Cutting Edge Green Building Methods and Materials (infographic)

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new construction methods - infographic


Screen Reader Version
Smarter and Greener: How cutting edge methods, materials and tech are making the world a more environmentally friendly and productive world.

Cutting Edge Construction Methods

Robot swarm construction

What is it? Researchers at Harvard have built small construction robots programmed to work together as a swarm to build structures.

How it works? The large swarms of robots can use artiificial intelligence to construct buildings, taking inspiration from insect swarm builders such as termites. Being a swarm, if some of the robots for some reason can’t work the others will still be able to complete the job.

What are the benefits? Quicker and safer construction of buildings without the need of human attendance on site. Perfect for constructions in dangerous places or space/colonized planets.

3D Printed Houses

What is it? Using giant 3D printers to build the main structural components of houses and other structures.

How it works? Giant 3D printers take raw materials and fashion them into buildings.

What are the benefits? Quicker construction and less production of waste in the building process. It is also thought that 3D printing may be how we build on the moon and other planets.

Is it being used yet? A small number of teams across the world are pioneering this method, including DUS Architects in the Netherlands, who are building a 3D printed Canal House that is under construction in Amsterdam and the Chinese company WnSun, that have built ten demo houses for $5,000 each.

Innovative Materials


What is it? Uses live micro algae growing in glass to generate renewable energy and provide shade.

How it works? The microalgae are supplied with liquid nutrients and carbon dioxide. They are then harvested to create biogas.

Where it’s being used? Arup have used this technology in the BIQ house as part of the International Building Exhibition in Hamburg, 2013.

Aerogel Insulation

What is it? One of the least dense substances in the world, Aerogel is almost as light as air and has super-insulating properties.

How it works? By removing liquid from gel you are left with the silica structure. This can be spun out to create sheets that have up to four times the insulating power of fiberglass or foam insulation.

What are the benefits? Better insulation in buildings could reduce the environmental burden of heating.

Is it being used yet? Recent reduction in the price of Aerogel has made it viable for usage in construction. Some predict it will soon take over the market in insulation.

Transparent Aluminum

What is it? Aluminum oxynitride or AION is four times harder than fused glass and 85% as hard as sapphire.

How it works? Aluminum oxynitride powder is stuffed into a rubber mourld and compressed in hydraulic fluid to 15,000 psi. It is then fused together by heating for days, then polished until clear.

What are the benefits? Although currently excessively expensive, it could be very useful in the construction of skyscrapers and in providing fire-resistant glass.

It is being used? It’s expense means it is more likely to be found in military tech than in the city.

Features of Smart Buildings

It’s not just materials that are making buildings better, technology is also playing its part

System integration – Systems that interact with each other can better understand, and respond to, the movement of people and resources around a building.

Environmental control – Smart building systems should be able to understand when lights and heating can be altered and turned off. This reduces wasted energy.

Data collection – By collecting data on how your office space is being used, a smart building can help you manage desk and office space more effectively.

Productivity benefits – By monitoring staff productivity through your building, it is possible to see what makes your staff more, and less, productive.

Buildings that Break the Mould

The Edge – Amsterdam

Often called the smartest building in the world, the Edge combines green building techniques with smart building innovation to create a place that’s great to work in and isn’t a burden on the environment.

Rating: Outstanding
BREAM rating : 98.36%

Electricity – 70% less electricity than comparable office buildings
Energy – The solar panels on the roof produce more energy than the building consumes
Heating – Aquifer thermal energy storage system provides all of the energy required
Water – Drained rainwater is used for cleaning and flushing the toilets
Lighting – LED lighting can be regulated via smartphones. Sensors measure occupancy and adjusts energy use.

The Crystal – London
The Crystal showcases state-of-the-art technologies to make buildings more efficient and more sustainable.

BREAM rating: outstanding

Energy – 20% of energy is from solar panels. 70% lower emissions.
Heating – 100% natural heat sources. Has 199 ground source heat pipes
Water – WC water is taken from non-potable sources, 80% of hot water is heated by solar heating and ground source heat pumps
Light – Triple-glazed windows let in 70% of natural light

Source: RubberBond

August 26, 2016 |

Public Works and the Importance of Creating Sustainable Communities [infographic]

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Communities both big and small are having a sustainable makeover in order to reduce energy demand, utilize renewable power, and lessen their environmental impact. This infographic provides an in-depth look at sustainable communities, highlighting their environmental necessity, as well as their financial practicality.

Infographic - Sustainable communities

Screen reader version:

Sustainability is a catchword in many industries, including farming, forestry and production. It’s a growing topic of concern in the development of public works including roads, sewer systems and parks, public buildings, where costs and lack of knowledge related to sustainability result in a general oversight regarding the issue.

In a world of diminishing resources, those tasked with planning and developing public works programs must be prepared to do so in a way that reduces energy demand, exploits renewable power and lessens the impact on our environment.

source: Norwich University’s Online Masters in Public Administration program

June 29, 2015 |

How to make rubber shingles out of old tires

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One day I saw a bunch of old tires used as a retaining wall and that got me thinking about what other uses old tires are good for. I had a few thoughts about what to make but I liked the idea of tire shingles the best. The fact that they would be malleable really hooked me. I couldn’t wait to get started!

About tires

The fabric of the tire is steel, nylon, aramid fibre, rayon, fibreglass, or polyester combination. The rubber is natural and synthetic (hundreds of polymer types). There are plenty of chemicals such as reinforcing chemicals, anti-degradants, adhesion promoters, curatives and processing aids such as oil. During my research I also found the typical percentages of the (synthetic rubber and natural rubber) rubber mix in various types of tires. Passenger car tires are 55 to 45 per cent, light truck tires are 50 to 50 per cent, race tires are 65 to 35 per cent, and off-highway tires 20 to 80 per cent.

Next I wanted to know what other environmental problems tires cause other than those related to their composition. I hadn’t thought about this but it makes perfect sense. I discovered that tires make the perfect breeding ground for mosquitoes. With all the diseases mosquitoes carry today tires are causing a potential threat to public health and safety.

Finally, I wanted to know what other methods of tire recycling are out there. I found a company called Rubbur Concepts that uses a compression mould to turn used tires into replica cedar and slate shingles. I also found that old tires are shredded and used in combination with asphalt to pave roads.

Materials for shingles

  1. 36 race car tires
  2. Sharp razor blades

Materials for roof

  1. (3) 3/4″ Plywood sheets
  2. (2) 8ft 2″x4″
  3. Screws
  4. Miscellaneous wood that I had


As you can see these are my clients. The owners of the chickens wanted the run of the coop covered. I discussed my idea with them and they agreed to let me build it. Little did I know . . .

Trial and error

As with any project there are always mistakes, or learning curves as some might say. So here is where I tell you about what didn’t work (for me). The initial tire concept was based on utilizing radial tires and that changed very quickly. The first tire I tried to cut was, to say the least, very smelly. I tried using a cutting wheel on the end of a drill (spinning at about 30,000RPM) and I found that while it would cut through the bead of the tire and all of the steel belts it wouldn’t cut the rubber, it just melted it. After breathing a cloud of burning rubber and trying it again wearing a breathing mask, I decided that it may not be the most “appropriate” method.

That particular method took about an hour and a half with only 8 small shingles being produced. The next method I tried was a jigsaw; it didn’t even cut through the rubber. The tire was too flimsy and would shake, so the jigsaw couldn’t cut it if the tire didn’t stay still. I didn’t even get one shingle out of that attempt. The last method I used on the radial tires was a hacksaw and let’s just say that it would have taken more than a year to cut the shingles that I needed. I then learned that there’s only one part of a radial tire that doesn’t have steel belts and that’s the side wall between the tread and bead. I did try to use a utility blade (box cutter) and cut just the side wall but it was harder to cut curves and keep them somewhat straight edged.

The method used

After several failed attempts with radial tires, I spoke with a local tire dealer and found that racing tires only have steel belts in the side walls, not in the tread. He happened to have an old tire so I took it home to see what I could do. I drilled a hole in the tread and used a key hole saw to start cutting. It went rather smoothly but it did take two people and still took about 45 minutes to make 12 to 14 shingles. I knew these were the type of tires I needed but I needed a lot of them, it turns out the guy at the local tire dealer knew someone who had a ton of old racing tires. Before I went to the store to buy brand new hole saws, I tried a utility blade (box cutter) (just for laughs actually) and found that it cut through the tire like a hot knife through butter (image 1). This method cut the time down to minutes. After cutting the side walls off, I had a round thin circle of rubber (image 2). Then cut it so it was a long flat sheet about 8” x 80” (image 3).

image 1

image 2

image 3

Now that I had a sheet of rubber all that was left to do was make the actual shingles. As you can see in image 3 I used a piece of chalk to mark where I needed to make the cuts and this is a good time to have someone with you. I averaged 14 shingles per tire and the shingles were 5″ x 8″. My friends and I used a method that we called “the bend and spread.” As you can see, below in image 4 the “bend” portion refers to actually bending the rubber strip to help keep the rubber from kinking while cutting. Image 5 is showing the spread part, while being cut the person bending the rubber should also help spread it so it’s easier and faster to cut. I didn’t time how long each individual tire took to cut, but with four people and in four hours we cut all 36 tires and made 460 shingles. I was very happy with the time results. Each tire produced about 2ft2.

image 4

image 5

image 6

The roof

As mentioned in the Clients/site section, I ended with “little did I know . . .”. Well, I didn’t think ahead with the weight factor. The run that was already built for the coop was way too flimsy to support these shingles. The shingles averaged 14 lb per 25 shingles and I had 460. Since covering the run was out, the owners and I needed to think of what we could do instead. They had a big enough garden and the chickens already had access to it so we decided to build a semi-portable roof and place it in the garden area. To the right is the sketch for the new roof and it required (2) 8′ 2″x 4″ and (3) 4’x 8′ plywood sheets.

image 7

image 8

Image 7 shows the assembly of the sides and front portion of the roof. The other parts of the structure are shown in image 8. All wood was assembled with reused screws and nails that the owners had. Also in image 8 you can see part of the removable roof measuring 6’x6′. The top of the roof was 4′ high and the lower portion was only 3′ high.

Shingle installation

The typical shingles you see on roofs are installed using tar paper, which helps ensure that water will not leak in. Also standard shingles are usually doubled up on the first row to help keep water out. The shingles were a bit thick (1/4″) so I was not able to double up, but I did find that the rubber is very tight against the nail and helps to seal the holes much more so than traditional shingles. In Images 9 and 10 you will see a plastic bag that I stapled down for a little extra protection and the process of installing the shingles. The owners did have some roofing nails but I ran out and had to buy a box to finish the project. I took about 14 hours of labour to nail all of the shingles in and it only took four hours to make them all.

image 9

image 10


In all, the design worked just as I thought it would. It was put through the Northern California rain test and there were not any visible leaks, although, water always finds a way. I was happy that I only spent $10 to make the shingles, the $10 was the purchase of several razor blades and utility knives. The structure itself was a bit more, but the main focus was the tire shingles themselves. This was a successful project, but that depends on your definition of appropriate technology. At the beginning of this class I thought the definition was that all other technology is inappropriate. I then formulated my definition to “our best effort in leaving the smallest environmental impact.” I now know that what is good for one person will not be good for another, so my definition has changed again: “Our best effort in leaving the smallest environmental footprint within the ways that we choose to live.”



While undertaking this project I had several ideas that I wasn’t able to implement or test.

  • The shingles did work fine, but if I was going to use them on my roof I would want them to be a bit more uniform and not so wavy. I need to find a way to cut straight lines; I had thought of a paper cutter, but this project needs something with more leverage and durability.
  • Another idea I had was to build a rain gutter to catch the water; then I could have it tested so I could know exactly what’s running off. Unfortunately, the funding for this project didn’t allow such an expensive test.
  • It might have made things easier if I had made the shingles bigger.
  • In case you’re wondering what happened to all 72 sidewall rings (image 11), I spoke to the guy who gave me the tires and it turns out that he also races go carts so he said he could use those to lay out track designs.

This project was carried out and written up by Brad Thompson. This article was republished from Appropedia.

Learn more:

March 10, 2014 |

Reviving a neighbourhood by building affordable sustainable housing

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Massachusetts Avenue Park was not a place you’d want to take your kids. Before, the small neighbourhood park in the heart of Buffalo’s West Side was little more than vacant land with a small playground and a crumbling basketball court. “It was a real mess,” says Terry Richard, a neighbourhood resident who was born in Trinidad and Tobago and later moved to Buffalo by way of Brooklyn. “So we figured … why don’t we just take this on as a task to really force the city’s hand to take care of their problem,” she adds, standing next to the park’s new playground with a bright smile.

Buffalo is located where the waters of Lake Erie feed into the swift currents of the Niagara River. It was established as a major grain shipping and storage centre in the late 19th century, but as shipping routes changed and heavy industry packed up and left the Great Lakes region, Buffalo’s population rapidly declined. In 1950, Buffalo’s population was about 580,000, but by the 2010 census it had fallen to about 260,000.

It isn’t just the population that’s been shrinking though: employment numbers are down, and like other Rust Belt cities, Buffalo has struggled to support its infrastructure with a shrinking tax base. The rebirth of Massachusetts Avenue Park echoes many other stories taking shape throughout the city. Instead of waiting for the city to make things better, residents like Richard are taking matters into their own hands.

Richard is a board member for People United for Sustainable Housing (PUSH), a grassroots organization based in Buffalo that seeks to provide affordable, environmentally friendly housing and job training.

In early June PUSH celebrated the opening of Phase 1 of the small but pleasant new Massachusetts Avenue Park, which resulted from about two years of petitioning City Hall to fund the project. The park is just one piece of PUSH’s broader plan to create a Green Development Zone within the West Side—a 25-block area where the group is developing sustainable, affordable housing and creating new career pathways for neighbourhood residents.

There goes the neighbourhood

Like many Buffalo neighbourhoods, the West Side is full of vacant properties, and PUSH co-founders Aaron Bartley and Eric Walker wanted to know why. When they launched the organization in 2005, their first order of business was to conduct a survey of Buffalo’s West Side, which meant going door-to-door in the community for about six months.

With a bit of digging, they discovered that a sub-agency of the New York State Housing Finance Agency was in control of nearly 1,500 tax-delinquent properties in the city—about 200 of which were on the West Side—that were being left to rot. In 2003, the state of New York’s Municipal Bond Bank Agency bought the delinquent tax liens for those homes, which were then bundled and sold as bonds to investment bank Bear Stearns.

But there was one major problem: According to a report published in Artvoice, Buffalo’s main alternative weekly, the assessed value of the properties was much higher than they were actually worth. In effect, the state was using vacant houses in Buffalo to speculate on Wall Street.

Meanwhile, nothing was happening with the houses; the state was neither maintaining them nor selling them. “There just was absolutely no due diligence done as part of the transaction,” Bartley said. “If there had been, they would’ve seen that bond was fraudulent.”

The value of bonds was based on revenue that was supposed to have been generated by the houses, through either selling them or collecting unpaid taxes. But the state made little effort to sell or collect taxes on the properties. Why? Because doing so would reveal the true value of the properties, according to Bartley, and the house of cards would come crumbling down. “The reason they didn’t do that is that would’ve shown the lie to the deal, because they would have sold for $0, and it would have indicated that it was worthless,” Bartley explained.

When Bartley and Walker made the discovery, they tried to bring it to the attention of state officials through standard channels, but when that failed they launched a direct action campaign. Using a big stencil, they painted an image of then-Gov. Pataki’s face on more than 200 houses across the city. Eliot Spitzer was campaigning for governor at the time, and he took an interest in the issue. When Spitzer took office, his administration unwound the bond, gave the houses back to the city of Buffalo, and created a small housing rehab fund. The houses were turned back into the city’s inventory, and when PUSH or one of its partner organizations wants to redevelop one, they ask to have it transferred.

The green zone

Two years later, PUSH invited hundreds of residents to a neighbourhood planning congress to draft a development plan for the largely blighted 25-block area on the West Side that would later become the Green Development Zone (GDZ). The plan went far beyond energy-efficient affordable housing to include the creation of employment pathways and promoting economic stability within the zone.

“Sustainability” in the context of PUSH’s agenda means reducing the neighbourhood’s environmental impact, but also strengthening the local economy and creating green jobs.

On the surface, the GDZ still looks similar to other Buffalo neighbourhoods: The streets are lined with 100-year-old two- and three-storey houses, and in the summer, they teem with people. Old ladies sit and talk on first-floor balconies, while kids weave in and out of slow-moving traffic on bicycles. But this small neighbourhood is in the midst of a pretty radical transformation.

“Sustainability” in the context of PUSH’s agenda means reducing the neighbourhood’s environmental impact, but also strengthening the local economy and creating green jobs in the building, rehabilitation and weatherization industries. PUSH was instrumental in getting the Green Jobs – Green New York legislation passed, which seeks to create 35,000 jobs while providing green upgrades and retrofits for 1 million homes across the state. PUSH recently established PUSH Green to implement the GJGNY program in the Buffalo area, functioning as an independent outreach contractor in the region. For the work, PUSH has established what it calls a “Community Jobs Pipeline,” a network of contractors who agree to provide job training, pay living wages and hire local workers from target populations.

Energy-efficient—and affordable too

In September, PUSH held a ribbon-cutting ceremony for three gut-rehab buildings with a total of 11 affordable housing units, bringing the total number of residential units PUSH completed in the GDZ to 19.

But the organization has much bigger ambitions. In December, PUSH announced plans to build nine new-construction buildings and to renovate seven existing properties, adding a total of 46 more energy-efficient, affordable units to the neighbourhood. “We’re very strategic in our development work, so we’ve taken a small section of the West Side, and we’re really trying to concentrate our development,” explained PUSH Development Director Britney McClain. “We don’t want to contribute to the scattershot development work that is also common in the city of Buffalo.”

Ensuring that the homes it produces are energy-efficient is an important component of PUSH’s work, because heating and energy costs account for a large percentage of living expenses in Buffalo. “A lot of the houses in this city are over 100 years old and poorly insulated, so to have an apartment at an affordable rate but also that is totally energy-efficient, through the new windows and insulation, the utilities bills will be drastically reduced,” McClain told me.

Green buildings enjoy lower operating costs, but they’re more common in luxury real estate portfolios than in the inner city. That’s a perception that PUSH is looking to change.

In 2011, PUSH completed a net-zero energy house—a home that produces as much energy as it uses. The project was launched to showcase renewable energy technologies and to help give low-income residents paid job training. In the process, the builders found another innovative use for vacant lots: they dug a deep trench in the adjacent lot to provide geothermal heating and cooling for the house. On all of the buildings, PUSH reuses existing materials where possible, upgrades the windows and insulation and installs Energy Star-rated metal roofs that help to passively cool the buildings.

Extreme neighbourhood makeover

Back at the PUSH headquarters I met co-founder Eric Walker, who I instantly recognized even though we had never met. Walker guest-starred on an episode of ABC’s reality TV show Extreme Makeover: Home Edition that aired in 2010. In a typical episode of the show, a handful of hyperactive celebrities and local volunteers target a distressed home that is owned by a family undergoing illness, disaster, or some other hardship, and they quickly fix it up for the family in need. Instead of just fixing up one house, though, PUSH and some 4,500 volunteers teamed up with the show’s producers to fix up several surrounding properties in the neighbourhood as well.

Extreme Makeover brought the West Side some positive national exposure, but Walker still has mixed feelings about the show. Neighbourhood improvement can either come from external forces or it can come from within, and the forces of change portrayed in the show weren’t entirely homegrown. “In organizing, we talk about three kinds of power: power over, power for and power with,” explains Walker. The TV show gave PUSH an opportunity to inspire, but the tools of change were in the hands of the ABC producers and the celebrity hosts—not members of the community. “It was one step removed from the power we’re trying to build,” Walker says.

The TV cameras packed up and left, but the transformational power remains in the neighborhood. It is evident in the carefully restored Victorians that line Massachusetts Avenue; in the raised beds the community has acquired through PUSH; and in the fact that parents now take their children to the once-dangerous park they fought for and won themselves.

Check out Eric Walker’s talk at TEDx Buffalo:

Mark Andrew Boyer wrote this article for YES! Magazine, a national, nonprofit media organization that fuses powerful ideas and practical actions. Mark is a photographer and writer based in the San Francisco Bay Area. His work has appeared in GOOD, Inhabitat, and Mindful Metropolis.

March 9, 2014 |

Building an eco-friendly cottage for $10,000

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Three years ago, I decided to downsize. I sold my big house (which I loved!), got rid of all my stuff, and built an itty-bitty eco-friendly cottage. When I finished building, I slid my little house into a friend’s backyard. This isn’t as odd as it sounds. My house actually “fits” in the backyard. It looks like a tiny cabin, or a tree house. It’s also super-small and built on wheels.

My house offers 84 square feet of living space and cost about $10,000 to build. It was built for the highway, but—honestly—it isn’t anything like a travel trailer. It doesn’t contain any space-age plastics or fake wood. Instead, it’s the real deal: knotty pine, cedar and fir.

I made the house to be as simple and natural as possible. I minimized my construction footprint by using a bunch of “green” building techniques, including:

Recycled and salvaged wood – The house took shape based on the materials that were offered to me or “found.” For example, I decided to install skylights after I found two huge windows at the salvage yard. I installed knotty pine siding on the interior walls and ceiling, and used cedar planks for the loft floor after the wood became available at the local reuse store. I installed exterior cedar siding after my neighbour offered me a bundle. He had originally purchased the wood in the 1940s, and had been storing it in his garage since that time. It was beautiful old-growth cedar—the kind you can’t find anymore.

Insulated windows – The house has nice, wood-clad windows that are low-emission (which reflects sunlight to keep the house cooler in the summer) and argon-insulated. They cost a mint, but have proven to work great! They cut noise and heat loss and look fabulous.

Solar electricity – A 240-watt photovoltaic (solar) system powers my lights and other electric gadgets. It was sized to meet my needs, based on Olympia’s cloudy weather.

Non-toxic stains and sealants – I used a water-based stain on the outside of the house and a water-based sealant on the kitchen counter. I didn’t coat the floors, walls, or ceiling. As a result, the house carries a subtle, natural cedar and pine smell. I love the woodsy, peaceful smell of my house.

Primitive water/sewer – I don’t have running water in my house. I pull water from a nearby garden spigot and jug it into the house. I use a composting toilet and I shower elsewhere. This “primitive” set-up has presented some of the greatest challenges for me. But I’ve gotten used to things, and I recognize that (on a world scale) any sort of toilet or shower is a blessing. Millions of people live without running water or a sanitary sewer. My situation is gifted by comparison.

Other good ideas – I used shredded cotton insulation in the walls and ceiling, and Marmoleum (a natural linseed product) on the floor. I placed the house in the backyard with consideration for wind, sun and shade. Most importantly, I simply minimized the size of the house while creating a sense of space, utility and natural beauty (smaller really is better for the environment).

I’ve been in the backyard for over two years. I didn’t intend to find myself stumbling down a “greener” path, but the house has worked on me. I buy less stuff (there’s no place to store it). I rethink leaving lights on and mull over better ways to manage my compost. I take fewer and shorter showers because I’m imposing on someone else. My ecological footprint has definitely gotten smaller by living in my little house.

I’ve saved a lot of money (my utility bills don’t really exist, and I don’t have a mortgage). I also spend less time fixing things and cleaning. Now, I have more of the “stuff” that I always wanted: time and resources.

I’ve tried to explain my house to other people. It’s a bit awkward. For example, a few weeks ago, a group of 5th-graders visited my house. I was trying to explain how my house works and what makes it “green.” And ultimately, we spent less time talking about the house (itself) and more time talking about how the house has connected me to the community.

I’m less autonomous. I rely on the sun to power my lights. I trust the rain on the roof to keep me company. I love that the wind cools my house in summer (it works!). I depend on the library and food co-op, and the generosity of friends and neighbours. I have to ask for water every day, and that has changed me!

I find myself wanting (more than ever) to give something back. And that is at the root of all sorts of new ways to live more simply and in-step with my world. Downsizing just keeps getting better!

Read more about small homes in SMALL AND SUSTAINABLE: Review of small and tiny home kits, plans and finished homes>>

Dee Williams’ tiny house was featured in Sustainable Happiness, the Winter 2009 issue of YES! Magazine. Dee is an inspector with the Washington State Department of Ecology.

Reprinted with kind permission from South Sound Green Pages. Interested? Dream House: Tour Dee Williams’ house
See the houseplan at

February 19, 2014 |

Green building pyramid [infographic]

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Screen reader version:

H20 and carbon zero – At the highest level of green building, the finished home recycles water and uses little or no outside energy. It may include geothermal heating/cooling, solar hot water, a wind turbine and/or photovoltaics.

Push the envelope – Several time-tested alternative structural systems offer higher R-values and other advantages over conventional stick framing. They include structural insulated panels (SIPs) and insulating concrete forms (ICFs), along with straw bale, cordwood and other systems.

Apply for green certification – Various organizations will “certify” your project’s green features, including the NAHB, USGBC and EarthCraft House. Some may argue that certification belongs lower on the pyramid, but earning that green stamp of approval will come easily if you have given attention to the bottom two-thirds of the pyramid.

Opt for low- or no-VOC paints

Reduce job-site waste/transport – Production and transportation of materials used in building a home account for only 6 per cent of its lifetime energy use. Reducing and recycling waste on the job is an important but relatively small player in a home’s long-term ecological footprint.

Program & zone HVAC

Select rated appliances

Lower H2O flow

Upgrade windows – At a minimum, windows in a new home should included insulated low-E glazings. Look for durable window frames made with materials that are renewable or recyclable and seal and flash them meticulously.

Upgrade HVAC

Opt for durability – Durability is a green characteristic. On the roof, opt for metal, clay tile, recycled rubber or extended life (recyclable) asphalt roofing. Side with fiber cement, cedar, brick veneer or other long-lived products. Build decks and patios with recycled plastic composites or long-lasting wood species. Indoors, specify durable countertops and floors made from renewable or recycled materials.

Insulate foundation – Uninsulated concrete foundations can reduce HVAC efficiency by 30 to 50%. Specify rigid or spray-on foam insulation or insulating concrete forms (ICFs) for best results. Consider a frost-protected shallow foundation or slab-on-grade construction.

Upgrade shell insulation – For stick-framed walls and ceilings, air infiltration is a major concern. Consider an insulation package that seals walls tightly, whether with spray foam housewrap or a combination of insulating materials. Specify 2×6 framing with 24″ stud cavities.

Siting – Well-designed site plans take advantage of free solar light and energy and minimize damage to existing plants and habitats.

Location – Automobile dependency is not a green asset. Build close to transit hubs.

Education – If you don’t understand basic green principles, you’re likely to make decisions you’ll later regret. Consider a course at Green Builder College ( or hit the books on your own.

House size – Doubling a home’s size triples its annual energy use for the life of the home. Think small and clever, not big and boxy.

February 1, 2014 |

BUILDING WITH PUMICE: How to build pumice-concrete houses [part 2]

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Part 2 of Building with Pumice (read part 1>>)

This chapter tells how to build several different kinds of houses using building members of the kind described. Typical, practical models that have already been successfully built in various countries were selected.

They include: one in-situ pumice-concrete house, three pumice-brick/block houses, two simple panel-wall houses and two houses made of wall-height hollow-core planks. All of them have approximately 5 – 6 m (= 30 m) floor space and are suitable for self-help construction.

House with in-situ pumice-concrete walls

Technical description:

This house has load-bearing walls made of in-situ cast pumice concrete. It rests on a reinforced concrete strip footing (normal-weight concrete, not pumice concrete) or on a natural-stone masonry foundation. The in-situ pumice-concrete walls are erected directly on the foundation. They are 15 to 25 cm thick and, to the extent necessary, reinforced with steel to provide protection against earthquakes. The massive walls can be rendered/plastered or smoothed with several coats of paint. The door and window openings are simply left free, and the door and window cases are embedded in the concrete. In-situ concrete walls have the advantage of not requiring prefabrication (like bricks or panels). On the other hand, they do require the installation of wooden form work to contain the concrete, which in turn involves extra expense, work and prior knowledge (Fig. 50). The roof substructure consists of lattice steel or wooden beams. The roof skin can be made of galvanized corrugated sheeting screwed down on wooden laths, although any other kind of roofing would also be suitable (e.g. clay roofing tiles, straw and reed, etc). The solid walls are strong enough to accommodate a ceiling for the possible subsequent addition of a second storey. The floor is made of thin concrete screed on a layer of sand and gravel. Wooden or steel frames hinged to the concrete—embedded cases are recommended for the windows and doors.

Pumice P41.GIF
Figure 50: Wooden formwork for in-situ pumice-concrete walls

This type of construction is most suitable for building new homes. Since it requires a substantial amount of formwork, it is appropriate for countries with adequate supplies of wood. Putting up formwork is no job for beginners, so the aid of specialists should be enlisted.

This type of house lends itself well to the construction of sizable housing developments by self-help cooperatives. The use of prefabricated forms that can be used repeatedly, together with the aid of trained specialists, can help maximize the effectiveness of the building effort.

The following list is a rough bill of quantities for the subject type of house. Local prices can be entered in the “price” column, thus allowing comparison with other house-building systems.


Quantities 4.1 House with pumice concrete walls Walls Prices
ca. 50 m² wall area Walls comprising 7.5 m³ pumice concrete for a wall thickness of 15 cm. A concrete mixing ratio of 1:4 will yield about 7.5 m³ pumice concrete for 1000 kg cement (20 bags weighing 50 kg each).
The same walls with a thickness of 25 cm require 12.5 m³ pumice concrete. For a mixing ratio of 1:4, about 1750 kg cement (35 bags weighting 50 kg each) are needed for 12.5 m³ pumice concrete.
70 m Reinforcing rods (approx. 10 mm diameter) for a peripheral tie beam, if the house is located in an earthquake area.
30 m Reinforcing rods for around the doors, windows and corners.
ca. 50 m² Wooden formwork, at least 2 cm thick for casting the walls. Suggestion: prepare forms with height of roughly 1.10 m and cast the formwork and pour the upper part. Wood for forms can often be borrowed, not necessarily bought.

Pumice P43.GIF
Figure 51 and 52

Pumice P44.GIF
Figure 53 and 54

Pumice P45.GIF
Figure 55: Section

Pumice P46.GIF
Figure 56: Isometric view

House with pumice-concrete solid-block/brick walls

Technical description:

In this case, the walls are made of masonry consisting of prefabricated pumice-concrete solid blocks/bricks. They can range in thickness between 10 and 25 cm, depending on the size of the blocks/bricks.

The strip footing can be made of in-situ normal-weight concrete or of natural stone masonry, as long as it’s strong enough to carry the weight of the walls. First of all, the blocks/bricks for the walls have to be made. Fifty bricks measuring 25 – 11.5 – 7 cm will produce one square metre of wall with a thickness of 11.5 cm. Only 7 blocks measuring 49 – 30 – 11.5 cm are needed per square metre wall area with a thickness of 11.5 cm. The pumice-concrete bricks are very light and therefore quick and easy to place. Care must be taken to ensure that the walls have the proper masonry bond and are exactly vertical (Fig. 57). It’s important to remember that pumice bricks have to be dipped in water prior to use to keep them from absorbing the gauging water and setting too quickly, which would result in very unstable joints. The walls of the house can be rendered/plastered and plinth rendering to a height of 30 – 50 cm is recommended in any case.

Pumice P47.GIF
Figure 57: Setting up brick walls

The top row of bricks should carry a peripheral tie beam of reinforced concrete or wood, so that a second storey can be added to the house at will. Walls with a thickness of about 15 cm will suffice for a single-storey house, but the wall thickness should be increased to approximately 25 cm for the first floor of a two-storey house (10 – 15 cm for the upper storey). The roof can be made of clay roofing tiles, corrugated asbestos, corrugated metal, wood, reed or palm fronds. The walls are sturdy enough to carry heavy roofing. The doors and windows can be made of wood or metal, and their cases should be tied into the masonry.

The house is very well-suited for self-help construction. One person alone can easily make the bricks/blocks since all that’s needed is a wooden mould, pumice, cement and water. After making just a “few” bricks, the same person can build the walls little by little. This type of construction involves no heavy work at all since more bricks can be made and placed whenever the builder has a few extra hours or days.

Quantities 4.2 Pumice-brick/block house Walls Prices
ca. 50 m² wall area For bricks measuring 24 – 7 cm and a wall thickness of 11.5 cm, 2500 bricks and about 700 kg cement (14 bags) will be needed to put up the walls.
ca. 2 m³ Masonry mortar, i.e. approx. 6 bags of lime/cement and approx. 2 m³ sand
(For a wall thickness of 24 cm and blocks measuring 49 – 24 – 11.5 cm, 800 blocks, 1400 kg cement (28 bags) and 2.4 m³ mortar consisting of approximately 7 bags of lime/cement and approximately 2.4 m³ sand will be needed for the walls.)

Pumice P48.GIF
Figure 58: Plan

Pumice P49.GIF
Figure 59 and 60

Pumice P50.GIF
Figure 61: Section

Pumice P51.GIF
Figure 62: Isometric view

House with pumice-concrete cavity-block walls

Masonry construction

Technical description:

The walls of this house are made of so-called two-cavity pumice-concrete blocks, which have the advantage of forming a strong and sturdy wall with less material than would be needed for a wall made of solid blocks. Additionally, the cavities have a good insulating effect in both cold and hot climates.

The foundation should be made of in-situ concrete or natural stone masonry and be 5 to 10 cm wider than the walls.

The first step in putting up the walls, of course, is to prefabricate the cavity blocks as described in section 3.2.3. The blocks are placed with the closed end up, i.e. such that the cavity openings are pointing downward. That way, it’s easier to spread the mortar around the edges of the last course before setting the blocks of the next row (Fig 32; cf. Chap. 3.2.3).

In earthquake areas, it’s a good idea to fill the corner cavities with reinforced concrete.

Pumice P52.GIF
Figure 63: Plan

The reinforcing bars should be embedded in the foundation at the corners. Then only the “tops” of the cavity blocks have to be neatly opened (Fig. 37, cf. Chap. 3.2.3), the blocks threaded onto the rods, and the cavities filled with (well-compacted) pumice concrete all the way up to the top of the wall. There, the reinforcing rods should be attached to a peripheral tie beam, which can be placed in special pumice channel blocks that are subsequently filled with pumice concrete (Fig. 43; cf. Chap. 3.2.6).

The door and window cases should preferably be prefabricated and built in; the walls can accept a second storey.

Pumice P53.GIF
Figure 64 and 65

The roof can be covered with clay roofing tiles, corrugated asbestos, corrugated metal, reed or palm fronds.

The door and window cases should preferably be prefabricated and built in as the walls go up in order to achieve a more stable connection between them and the masonry. If that’s not possible, a few pieces of wood, screws or the like can be embedded in the masonry joints at strategic locations to provide anchorage for the subsequently placed door and window frames. The floor can be executed in any desired fashion, although the installation of a layer of gravel covered by a thin layer of concrete screed or a bed of sand followed by ceramic floor tiles is recommended.

Pumice P54.GIF
Figure 66: Section

Pumice P55.GIF
Figure 67: Isometric view

Fair-faced concrete-column skeleton structure

Technical description:

This type of structure consists of a load-bearing concrete-column skeleton filled out with pumice-concrete cavity blocks.

The house rests on reinforced-concrete isolated or strip foundations with encastre concrete columns. The pumice-concrete cavity blocks fill out the spaces between the columns. The floor of the model house consists of a layer of sand and gravel topped with a thin layer of concrete screed. The roof substructure is made of lattice steel or wooden beams. The covering may consist of roofing tiles’ sheet zinc or corrugated asbestos sheet on wooden laths. The window and door openings have built-in cases made of square timbers or steel. The door leafs and window sashes are hinged to the case frames.

This model house is of very sturdy, durable design and can be added onto or altered at will, since any infill wall can be torn down and moved with no special effort. It’s relatively complicated to build, however, and therefore less appropriate for individual do it-yourself builders than for joint-effort projects of rural communities or building cooperatives.

Pumice P56.GIF
Figure 68: Plan

GATE has already sponsored the construction of such model houses in El Salvador and Nicaragua. This type of pumice-concrete block house is nearly identical to GATE’s “concrete column house,” for which detailed self-help instructions are available.

Pumice P57.GIF
Figures 69 and 70

Quantities 4.3 b) House with pumice-concrete cavity-block walls; fair-faced concrete-column skeleton Walls Prices
ca. 2 m³ Reinforced concrete for the concrete skeleton with 15 – 15 cm columns
ca. 50 m² Pumice-concrete block walls consisting of approx. 400 pumice-concrete cavity blocks measuring 49 – 24 – 15 cm (wall thickness: 15 cm)
ca. 1 m³ Masonry mortar for the joints, consisting of approx. 3 bags of lime/cement and 1 m³ sand

Pumice P58.GIF
Figure 71: Section

Pumice P59.GIF
Figure 72: Isometric view

House with pumice-panel walls

Sectional steel load-bearing system

Technical description:

This structure essentially consists of steel channel sections with pumice panels in between.

The house rests on a reinforced-concrete strip foundation with cutouts for the steel channel sections (or profiles made of galvanized sheeting). The cutouts are filled with concrete after the walls are properly squared.

Four wall panels of the kind described in Chapter 3.2.4 are stacked on edge between each two uprights, producing a rigid wall element measuring 2 m in height and 1 m in width (cf. relevant isometric drawing).

The wall structure gets its stability from the strip foundation at the bottom and a continuous tie beam in the form of a steel channel track at the top (cf. details in the relevant technical drawings).

The steel tracks are joined at the corners by riveting or welding (cf. 1:10 details in the relevant technical drawings).

Openings for windows and doors can be placed as desired simply by leaving out the appropriate pumice-concrete panels. The window and door cases are made of simple square timbers of the same thickness as the panels set in the channel sections.

The floor comprises a layer of coarse gravel, a layer of sand and a layer of smooth concrete screed.

The roof consists of zinc sheeting nailed onto a wooden substructure, although any other suitable material could also be used.

GATE has also published instructions for building this house (under the name “concrete panel house”); the instructions are available from GATE on request.

Bill of quantities:

Quantities 4.4 a) House with pumice-panel walls; sectional steel load-bearing system Walls Prices
ca. 3 m³ Concrete for strip foundations
ca. 4 Reinforcing cages appropriate to the foundation
ca. 44 Steel channel sections with a length of about 2.40 m and a profile thickness of about 3 mm for wall construction
ca. 76 Lattice-reinforced pumice-concrete panels (100 – 50 5 cm) as wall elements
ca. 4 Wooden, concrete or steel tie beams with cutouts for steel channel sections
ca. 30 m Boards for gable formwork
ca. 0.4 m³ Wood for the roof substructure and lathing
ca. 30 m² Corrugated metal sheet roofing or equivalent material

Pumice P61.GIF
Figure 73: Plan

Pumice P62.GIF
Figures 74 and 75

Pumice P63.GIF
Figure 76: Section

Pumice P64.GIF
Figure 77: Isometric view

Pumice P65.GIF
Figure 78: Details

Wooden post and beam system

Technical description:

This house is built according to the same basic system as the preceding house, except that the frequently very expensive steel channel sections are replaced by relatively inexpensive wooden posts and beams. While the model house has corner posts measuring 10 – 10 cm and intermediate/interior posts and tie beams measuring 7 – 10 cm, the wooden-post cross sections ultimately depend on the thickness of the pumice-concrete panels. The posts should consist of sawn wood that has been treated against pests with chemical agents, tar, used oil, lime, saltwater, etc.

Cutouts of adequate size are left for the wooden posts in the natural-stone or concrete strip foundations. The posts are inserted into the cutouts and wedged in place. Later, the cutouts are filled with concrete. Thin laths nailed onto the wooden posts hold the panels in place. One lath can be left out at first to allow easier stacking of the panels. Only when all of the panels are in place and properly aligned should the last lath be nailed on. The horizontal joints between the panels can be closed with mortar (= grout).

Pumice P66.GIF
Figure 79: Plan

This structural system is particularly well-suited for use in areas with easy access to cheap wood. The wood in question does not have to be straight lumber. If the wood is a little crooked, the pumice-concrete panels can be made to conform, and any residual openings can be sealed off with pumice mortar.

It’s important that the wooden posts be rigidly anchored at top and bottom.

Since pumice-concrete panels are very easy to make, and since the wood and pumice-concrete are both easy to work with and mutually adaptable, the house can be built as a family-scale self-help project.

Pumice P67.GIF
Figure 80: Detail of plan

Quantities 4.4 b) House with pumice-panel walls; wooden Walls Prices
ca. 22 Wooden posts, approx. 10 – 10 cm, 7 – 10 cm
180 m Wooden laths, approx. 2 – 3 cm or 2 – 4 cm, as “guide rails”
ca. 64 Pumice-concrete wall panels, 100 – 50 – 5-8 cm, requiring: 2.50 m³ pumice concrete, i.e. 350 kg or 7 bags of cement
ca. 0.20 m³ Mortar for horizontal joints between the panels
ca. 26 m Wood for the continuous tie beam, approx. 7 – 10 cm or 12 – 12 cm

Pumice P68.GIF
Figures 81 and 82

Pumice P69.GIF
Figure 83: Section

Pumice P70.GIF
Figure 84: Isometric view


House with wall-length reinforced pumice-concrete hollow-core planks as self-supporting wall members

Technical description:

This house has no load-bearing skeleton structure. The thick, wall-length self-supporting, hollow-core planks suffice to yield a stable house (as long as the planks are at least 7-15 cm thick). Such planks are rather heavy, requiring several people or special-purpose tools for handling and placing them. Consequently, this house is most suitable for housing projects involving several appropriately equipped professionals.

The house needs a solid natural-stone or reinforced-concrete foundation. The planks are easy to make, once a good set of moulds has been prepared (cf. Chapter 3.2.5). It’s important that the planks be cast properly and true-to-size, otherwise they may not fit together. Placing consists of erecting one plank after another, beginning at a corner of the house and propping each plank with wooden stays. As soon as one side of the house and its two corners are standing, the joints between the planks can be grouted with thin pumice-concrete containing only very small aggregates. Care must be taken to ensure that the entire joint is properly filled and compacted from top to bottom. A continuous tie beam made of normal-weight concrete must always be installed around the top of the walls to help hold the planks together. The roofing can consist of any preferred material.

If all planks are properly joined and plumb and if the foundation is strong enough, this type of construction can accommodate a second story.

Bill of quantities:

Quantities 4.5 House with wall-length reinforced pumice-concrete hollow-core planks as self-supporting wall members Walls Prices
ca. 50 m² Hollow-core plank walls, 10 cm thick, i.e. 38 hollow-core planks measuring 220 – 50 – 10 cm and comprising 3.42 m³ pumice concrete (approx. 500 kg or ten 50-kg bags of cement)
ca. 1 m³ Fine-grain pumice concrete for grouting the joints and casting the continuous tie beam
ca. 150 m Reinforcing rods, 3/8″ diameter for tie beam and joints

Hollow-core planks 50 – 205 – 10 cm

Pumice P72.GIF
Figures 85 and 86

Pumice P73.GIF
Figures 87 and 88

Pumice P74.GIF
Figure 89: Section

Pumice P75.GIF
Figure 90: Isometric view
Hollow-core planks 30 × 205 × 12 cm

Pumice P76.GIF
Figures 91 and 92

Pumice P77A.GIF
Figures 93

Pumice P77B.GIF
Figures 94

Pumice P78.GIF
Figure 95: Isometric view

Building with unbonded pumice

In many Third World countries, bonding agents like cement and lime are disproportionately expensive. In the late 1970s a mason in the Federal Republic of Germany had to work about 20 minutes to earn enough to pay for a bag of cement. At the same time, a mason in Guatemala, India or Bangladesh had to work three days to earn the “same” bag of cement. In terms of wages, cement was roughly seventy times as expensive there as it was in the Federal Republic of Germany.

That fact prompted the Research Laboratory for Experimental Building at Kassel Polytechnic College to investigate the question of how natural building materials like sand and gravel could be used for building houses without the necessity of using such binders. The use of fabric-packed bulk material was found to be the most cost-efficient approach. In that connection, various ways of producing and applying such materials had to be developed and tested. Pumice proved to be an exceptionally good bulk material for such applications, because it weighs less and has better thermal insulating properties than ordinary sand and gravel.

The first trials were conducted in 1976. Figure 96 shows a 2.20 m high column with a frustum-shaped shell made of PVC-coated polyester. Open at the top, the column is rendered stable by the bulk filler and its conical shape. The internal pressure generated by the filling stretches the jacket tight and keeps it from collapsing. The column’s load-bearing capacity depends on the tensile strength of the jacket. The column shown in the photo is capable of accepting a load of more than 10 kN (1000 kg). As shown in Figure 97, a load-bearing arch can be made by filling an arch-shaped fabric tube with sand -the only trouble being that filling the tube is very time-consuming.

In 1977 a dome-shaped experimental structure made of fabric-packed bulk material was erected on the research laboratory’s test grounds

The structure is 3.20 m high, has an outside diameter of 4 m and consists of 220 m of thin polyester hoses. The hoses are filled with the aid of a vacuum cleaner-driven bag filler of in-house design (Fig. 98). A pair of vacuum cleaners draw the bulk material into an elevated funnel (up to 3 m high). The bags are attached to the bottom end of the funnel. When the vacuum cleaners are turned off, a gate at the bottom of the funnel opens automatically, letting the bulk material fall into the hose.

The empty hoses have a diameter of 20 cm; after filling, they take on a elliptical shape, i.e. about 11 cm high and 25 cm wide. The structure is erected by placing the hoses on top of each other in concentric rings of decreasing radius. The dome-shaped structure has a cross section that roughly corresponds to the shape of an inverted catenary. The desired shape is obtained with the aid of a rotating vertical template mounted at the centre of the structure.

The round opening at the top is reinforced with a supplementary steel-pipe compression ring and covered with a mushroom-shaped member that can be raised for venting. Filling the hoses takes about 7.5 man-days, and the erection work, including manufacture of the compression ring and cover, takes approximately 12 man-days.

Based on experience gathered during that project’ the research laboratory designed and tested an earthquake-proof stacked-bag type of construction in Kassel in early 1978 (Fig. 100 and 101). The basic element consisted of 2.5 m long bags made of 0:5 m wide strips of burlap and filled with pumice gravel. The hose-like bags were knotted at the ends, bent double and stacked to yield 1.2 m wide wall members. Thin bamboo poles were pounded through the bags and fastened to a continuous tie beam (made of slender pine poles) at the top to make the stack stable. Several coats of whitewash were applied to keep the fabric from rotting and the wall from soaking up precipitation. Subsequent trials showed that it’s a good idea to immerse the bags in lime slurry prior to use.

In connection with a joint research project conducted by the Research Laboratory for Experimental Buildings’ the Francisco Marroquin University in Guatemala, and the Centro de Estudios Mesoamericano Sobre Tecnologia Apropiada (CEMAT), a 55 m² house made of stacked bags filled with pumice sand was erected in Guatemala in 1978 (Fig. 102 -105). This type of construction draws on prior experience with the aforementioned stacked-bag type of construction and was modifed as necessary to satisfy local requirements in Guatemala.

The basic structural member for this system was a hose-like bag made of cotton fabric with a diameter of about 10 cm and a length of anywhere from 1.70 to 2.80 m. The bags were filled with pumice sand and gravel, then stacked and pressed together so that the originally round bags took on a rectangular cross section measuring roughly 8 – 10 cm with round edges. The bags were first dunked in whitewash and then stacked directly on a 0.1 m-wide and 0.8-1.0 m-high strip foundation/plinth made of natural stone masonry. Immersing the bags in whitewash prior to use ensures that the cotton fabric is saturated with lime as protection against rotting.

Vertical bamboo poles placed at intervals of 0.45 m on both sides of the bags and interconnected with wire loops gave the stacked bags the necessary stability. The bamboo rods were fixed to the foundation and to the horizontal tie beam at the top.

Additional stability was provided by thick, round or square timbers (6 -8 cm diameter) that were rammed 0.3-0.5 m into the ground at the end of each stack of bags (ca. 2.25 m). This wall-building system is flexible enough to accommodate the motion induced by an earthquake. The continuous tie beam at the top keeps individual wall members and the entire system from falling over. After the walls were finished, they were given two coats of whitewash inside and out to keep rain from soaking into the bags. Table salt and alum were added to the whitewash to improve the vapour diffusion capability of the finished coating and to protect it against the digestive attack of microorganisms (1 bag of lime to 4 kg table salt, 2 kg alum, and approx. 30 litres water).

With reference to seismic stability, the purlin roof structure was separated from the wall structure. It rests on six roundwood columns with interconnection provided by wooden struts.

The building materials for the 55 m² house cost US .78, or US .46 per m².

It took 6 -8 workers about three weeks to build the house, meaning that labour only accounted for some 20 -25 per cent of the total cost of construction.

Compared to a similar house built according to customary methods using cement-bonded cavity blocks, this house took about the same amount of time to build, but cut the cost of building materials by 48 per cent.

A different earthquake-proof mode of construction for fabric-packed bulk materials was developed by the research laboratory in 1977 and tested on an experimental structure in Kassel (Fig. 106). This type of fabric-packed bulk-material wall comprises two rows of roundwood poles that are tilted toward each other and separated by two strips of fabric that are either sewn together at the bottom or nailed onto a lath and then filled with pumice gravel. The lateral pressure exerted by the bulk material is contained by driving the wooden poles into the ground and tying the top ends together. The 4-8 cm-thick poles are 2.10 m long and spaced at 0.45 m intervals.

The walls are 0.45 m thick at the bottom and 0.20 m at the top. As protection against ground moisture and splashing water, the walls were built on a cat 0.3 m-high plinth. The fact that the vertical poles are fastened to a flexible round-wood or bamboo-pole tie beam at the top and inclined toward each other on all sides ensures adequate stability to cope with vertical and horizontal seismic ground motion.

As shown in Figure 107, such wall members can be prefabricated. Rolled together, the poles and fabric making up a 10 m long section of wall turn into a single roll measuring 2.5 m in length and 0.5 m in diameter. This “shell” is easy to handle and haul, e.g. in a pickup, can be erected in a short time by two people, and then just has to be filled with loose pumice and sand.

December 14, 2013 |

BUILDING WITH PUMICE: Making blocks out of pumice, lime and concrete

Comments Off on BUILDING WITH PUMICE: Making blocks out of pumice, lime and concrete

Pumice P07.GIF

Everyone would like to live in his own home. Many people in industrialized countries occupy apartments in multistorey buildings.

This situation involves lots of problems for which there’s no immediate solution. This book is intended to stimulate interest in a line of approach to such problems by describing how to build simple, inexpensive houses out of a very commonplace raw material, namely pumice, i.e. volcanic glass or hardened volcanic froth. Such homes can be constructed on a self-help basis by individual builders, as cooperative efforts, or on an industrial scale. Which building components can be made of pumice and how those components can be put together to make a house is described in the following chapters.

We will be referring throughout to a basic model with roughly 30 m² floor space, for which the requisite building material costs approximately US . Such houses could serve well and be affordable as a minimum size dwelling for a family of six or less (Fig. 2). The described home-construction systems can be enlarged, built onto and/or modified at will, depending on the prevailing architectural style, the family’s space requirement and their given financial situation. The building materials for the house do not have to be bought or made all at once, but can be accumulated or put together little by little. With a bit of handicraft skill, it’s relatively easy to make the most of the building material assuming, of course, the builder has access to and knows how to handle pumice (or volcanic ash), cement, water and a few elementary tools.

The best way to tackle the job is for several prospective home builders to team up with each other to jointly plan, organize and implement their own building projects.

The main purpose of this book is to give practical information on the use of pumice as a building material and on organizing one’s own home building project. Naturally, no individual solutions can be offered for problems concerning the purchase of property or the financing, obtaining a building permit or actual construction of the house.

Building material for a house can be made from any number of raw materials, such as straw, reed, rocks, soil, wood, metal, depending on what’s available within a reasonable distance, for which climate the house is being built, and which culture-dependent conceptions it will have to incorporate. Pumice, too, is a good raw material for use in making building members. Pumice is not found everywhere, but only in the vicinity of extinct or still-active volcanoes, e.g. in Central America, East Africa, East Asia and Europe (Fig. 3).

Pumice P08.GIF
Figure 3

Europeans have always used pumice in residential buildings and industrial structures and continue to do so. As a building material in general it’s very popular, particularly in the near vicinity of the deposits.

The dissemination of knowledge and the transfer of technology concerning the production of pumice building materials should help developing countries establish their own indigenous production of inexpensive, versatile building materials. This book hopes to stimulate the utilization of existing resources in the form of volcanic ash/pumice deposits while also providing practical guidance for the production of building members for low cost homes.

Turning pumice into building material

All pumice building members can be made using simple craft skills. No complicated (and therefore expensive) machinery is needed.

What are needed most are a wood or metal formwork, a wheelbarrow, a shovel, a trowel and a level area for shaping and drying the pumice building members. Cement or lime, sand and water must also be available.

Producing one’s own pumice building members can always be recommended where the raw material is sufficiently inexpensive or, even better, available free of charge and the building is to be put up on its own, where there is solid foundation soil, and the builder/owner has some skill and prior experience in handling building materials.

It’s important to know that pumice building members are very durable if made properly and that they’re particularly suitable for dry climates.

As mentioned above, the materials needed to build a pumice home with 30 m² floor space cost roughly US . Add to that, of course, the cost of the property and any wages paid to helpers or contractors. For making one’s own wall members from pumice, the raw material should be available within a radius of 30 km (Fig. 4).

Pumice P09.GIF
Figure 4: Maximum distance between deposit and building site

Further information on rules and regulations governing home construction can be obtained from:

  • cooperative building societies
  • building authorities
  • credit institutions
  • architects
  • missions

What is pumice?

Pumice is a very porous form of vitrified volcanic rock, usually of very light colon. Its true density, i.e. the density of the powdered material, amounts to between 2 and 3 kg/ dm³ and its bulk density, i.e. the density of the loosely piled material, amounts to between 0.3 and 0.8 kg/dm3. In other words, pumice is very light. It has roughly the consistency of a mixture of gravel and sand, with light, porous individual granules that normally either float on water or sink only slowly. Pumice particles are either round or angular and measure up to 65 mm in diameter. Only particles in the 1 -16-mm size range should be used to obtain good building material.

Pumice P10.GIF
Figure 5: A volcanic eruption

In addition to light-coloured pumice, there are also various dark-coloured forms referred to as lava, tuff, etc. They, too, can be used as building material, but the light-coloured pumice processes better, as described in Chapter 2.4.

Pumice has the following chemical composition:

silica SiO2 approx. 55%
alumina Al2O3 approx. 22%
alkalies K2O+Na2O approx. 12%
ferric oxide Fe2O3 approx. 3%
lime CaO approx. 2%
magnesia MgO approx. 1%
titania TiO2 approx. 0.5%

Pumice originates during volcanic eruptions, when molten endogenous rock is mixed with gases before being spewed out (Fig. 5). The light, spongy particles are hurled up and carried off by the wind. As they cool and fall back to Earth, the particles accumulate to form pumice rock or boulders. Sometimes the molten rock is too heavy to be ejected, in which case it flows out and collects at the foot of the volcano as a compact, fairly homogeneous, usually somewhat less porous rock formation. Most such lava deposits can be cut up into natural stone blocks for direct use in construction work.

Where is pumice found?

Most pumice is found on the downwind side of volcanoes (Fig. 6).

Pumice P11.GIF
Figure 6: Pumice deposits on the downwind side of a volcano

The average deposit is loose, with a layer thickness ranging from 50 to 300 cm. Pumice should always be extracted under expert supervision and not haphazardly; otherwise, the results will look like Figure 7. The thickness of the pumice strata decreases with increasing distance from the center of the eruption.

The size of pumice particles ranges from superfine powder (0-2 mm) to sand (2-8 mm) to gravel (8-65 mm). The particle porosity can reach 85%, meaning that 85% of the total volume consists of “air” and only 15% of solid material. Its high porosity gives pumice good thermal insulating properties and makes it very light.

Old pumice deposits in areas with once-active volcanoes are covered with a 0.2-1 m thick layer of humus. When quarrying it, care must be taken to ensure that no humus is mixed into the pumice. If a large area is being mined, e.g. for a housing project, the humus should be replaced afterwards to prevent erosion and consequent ecological damage.

Additional site-specific information on pumice deposits is available from the various national geological institutes and/or soil research offices.

Pumice P12.GIF
Figure 8: Pumice extraction

What properties does pumice have?

Pumice has excellent properties. As a building material it is:

  • very light
  • inexpensive
  • refractory
  • resistant to pests
  • easy to work with
  • sound-absorbent
  • heat-insulating
  • temperature-balancing (Figs. 9, 10 and 11)

But it also has some negative properties like:

  • the lower compressive strength of pumice concrete, as compared to concrete containing other, heavier aggregates
  • the tendency of its edges and corners to break off more easily than those of heavy concrete
  • its lack of frost resistance when wet

Consequently, pumice building material should not be used for:

  • foundations
  • components with constant exposure to water, e.g. in showers
  • components subject to heavy traffic, e.g. stair treads and floor tiles

Pumice P13.GIF
Figures 9, 10, 11

How can pumice be made into building members?

A few expedients that facilitate working with pumice are required for turning it into building members, e.g.:

– some means of hauling the pumice from the deposit to the building site (Fig. 12);

Pumice P14A.GIF
Figure 12: Various means of transportation

– various tools like a wheelbarrow, shovel, buckets, saw, hammer, nails, spirit level, a folding rule, trowel, plumb bob, set square, plastic sheeting, etc. (Fig. 13).

Pumice P14B.GIF
Figure 13: Various tools

– an adequate supply of natural pumice (amounting to, for example, about 5600 kg, or 7 m³ for a house with 30 m floor space). A wheelbarrow holds about 0.15 m³, meaning that about 45 wheelbarrow loads would be needed to build the house;

– wooden moulds for bricks, moulds, etc. and/ or a press for making cavity blocks (Fig. 14: cf. Figure 34, p. 31).

In addition, a roofed-over, level work area is needed. The pumice being processed should have a particle-size distribution of 1 – 16 mm. The requisite cement should be Portland cement with normal compressive strength, to which lime or pozzolana can be added. Pumice building members can also be made exclusively with lime, as described in Chapter 3. The cement and lime must be kept dry, and there should be enough on hand to last for a full week of work. The gauging water should be clean; unpolluted rainwater is well-suited. How to make the moulds is described in Chapter 3.

In general, pumice building members are classified as lightweight concrete, since they are produced and processed in a similar manner, the main difference being that the aggregate—namely the natural pumice—is very light, porous and water-absorbent, so that such material has to be worked somewhat differently than normal-weight concrete.

As a rule, natural pumice is first saturated with water and then mixed with cement or lime, poured into the prepared moulds, compacted (either manually or by mechanical means), removed from the mould and stored to set and cure.

What sets pumic material apart from normal-weight concrete is that pumice concrete is usually soil-moist, i.e. used with relatively little gauging water and only small amounts of fine-grain aggregate—enough to cover the pumice particles with cement paste, but not enough to fill the cavities between the particles of aggregate. Consequently, pumice building components normally have a porous not quite smooth surface like that of nor mar-weight concrete. If so desired or necessary, e.g. for facade tiles, fine aggregate like sand can be added to obtain a smooth surface.

What kind of buildings can be made of pumice?

Pumice-based material can be used for building various kinds of structures:

  • single-storey homes
  • apartment buildings (up to four storeys)
  • workshops and storehouses
  • schools

Pumice P15.GIF
Figure 15: What kind of buildings can be made?

This book deals with the construction of single-storey homes, for which pumice building materiel can be made into (cf. Fig. 15)

  • pumice concrete solid blocks (solid pumice bricks),
  • pumice concrete cavity blocks,
  • pumice tiles,
  • pumice panels/planks,
  • in-situ pumice concrete,
  • special-purpose pumice building members (cf. Chapters 4.6 and 5)

Chapter 3 describes how prefabricated pumice wall members can be used for building houses.

Pumice-plank and pumice-panel homes are houses made of prefabricated members. After laying the foundation, the individual members (mainly the wall members) are prepared and used to erect the house on the foundation slab. This mode of construction is expecially well-suited for collective self-help measures in which several families wish to build the same kind of house, because erection of the plank or panel walls requires the work of several people at once (Fig. 16). One of the main advantages is the comparatively short erection time.

Pumice-concrete brick houses are built in a similar manner to heavy-clay brick houses, i.e. the masonry consisting of relatively small pumice bricks is built up on a solid foundation in the traditional manner. This method yields very individual homes and serves well for renovating or expanding existing homes.

Precast pumice-concrete building members

This chapter offers some practical self-help information on how to make and use simple pumice building components and members.

The following activities are explained:

  • making simple pumice-concrete solid bricks
  • making simple pumice-concrete cavity blocks
  • making simple pumice-concrete wall panels
  • making wall-length reinforced pumice concrete hollow-core planks

Such building members can be made using elementary do-it-yourself techniques without complicated tools and implements and may then be used for building a simple home.

The essential raw material is, of course, pumice. Consequently, the first step should be to find out where the raw material can be obtained, either by quarrying it or buying it from an inexpensive source. Then comes the decision as to how well the Chapter 2.3 conditions are met, and whether or not one’s own handicraft skills and available time will suffice for making the pumice concrete needed for the prefabrication work (solid or cavity bricks, planks or panels).

Pumice P17.GIF
Figure 17: Pattern for sketching out a self-help builder’s home.

In preparing one’s own pumice-concrete home building project, the following checklist could be valuable:

My property has an area of … m².

Pumice is available within a radius of … km. I have the means to buy and haul cement and lime. 1 bag costs US ..
There is an adequate supply of water located … km away.

I either own or can borrow the following tools:

  • shovel
  • pick
  • hammer
  • bucket(s)
  • wheelbarrow
  • trowel
  • nails
  • boards
  • saw

I have either made concrete before or know a mason and one or two friends who would be willing to help me make the building members and erect my house.

Enter your own ideas for a house in Figure 17. There are many ways to design a floor plan, depending mainly on the nature of the property upon which the house is to be built. Figure 18 shows several examples of common floor plans as a guideline. Fill in the following list as a basis for calculating the cost of construction:

The house I am planning to build has :

….. m² floor space,
….. m² wall area,
….. windows measuring ….. cm by ….. cm,
….. doors measuring ….. cm by ….. cm, a floor made of …..
….. m² roof made of ….. other important characteristics:

The property for the house will cost an estimated US …..

In order to calculate the quantities of building material needed for the house as planned, the following technical data must be known:

– 1 m³ pumice concrete contains:

  • 3 bags of cement (= 150 kg)
  • 600 kg pumice material
  • 250 litres of water

– The same cubic meter of pumice concrete will yield:

approx. 500 solid bricks (24 — 11.5 — 7 cm), approx. 120 cavity
blocks (40 — 15 — 20 cm with 2 cavities),
approx. 25 pumice panels (100 — 50 — 7 cm), 12 wall planks (200 — 50 — 10 cm, with cavities),

or, in other words:

– One bag of cement (50 kg), 200 kg pumice and 80 litres of water are needed to make 0.33 m³ pumice concrete.

– Thus, 1 bag of cement is enough for making:

165 solid bricks (24 — 11.5 — 7 cm),
40 cavity blocks (40 — 15 — 20 cm with 2 cavities),
8 pumice panels (100 — 50 — 7 cm),
4 wall planks (200 — 50 — 10 cm with cavities)

For a house with 30 m³ floor space, the following quantities are needed:

2500 solid bricks (24 — 11.5 — 7 cm) or
500 hollow blocks (40 — 15 — 20 cm with 2 cavities) or
64 pumice panels (100 — 50 — 7 cm) or
36 wall planks (200 — 50 — 10 cm with cavities)

Pumice P19.GIF
Figure 18: Selection of four 30 m² plans


How is pumice processed?

The pumice gravel is screened to separate the coarse and fine fractions and remove soil contamination. Then, the pumice is mixed with carefully measured amounts of cement and water to produce a batch of lightweight concrete. Careful mixing is very important for ensuring that the pumice concrete will be of uniform quality.

The mixture is filled into moulds (the dimensions of which vary, of course, depending on what kind of building member is being made) and then compacted by shaking and tamping. Then, the moulds are carefully removed and the block (or plank, panel, brick, etc.) is laid out to dry. After four or five days, the individual pieces can be stacked and left to cure and dry for at least another four days. After another 20 days, they are sufficiently transportable and can be used any time after that. Walls made of pumice members should be rendered/stuccoed to obtain a smooth finish and keep water out of the masonry. (The processing of pumice building members is shown schematically in Figures 19 and 20.)

Pumice P20.GIF
Figure 19: Production process for pumice building members (part 1)

The proper mixing ratio is achieved as follows: first, put together a suitable particle size blend. The heavier the end product should be, the more fine material and cement you will need.

Pumice P21.GIF
Figure 20: Production process for pumice building members (part 2)

The consistency of the mixture should always be such that the large particles touch each other, providing mutual support, while the fine aggregate materials more or less fill in the spaces in between. Good pumice cement usually consists of four parts mixed pumice, one part Portland cement and one part clean water. Mix the parts by hand or in a mixing machine until the material takes on the appearance of soil-moist light weight concrete of uniform colon.

Use the mixture as quickly as possible (within 30 minutes at the most) and do not let it even begin to dry out beforehand. In most cases, the described mixing ratio will be just right. If, however, the pumice is already moist and/or has a less-than-optimal particle-size composition, add more pumice, sand, cement or water as necessary (cf. Fig. 21).

Pumice P22.GIF
Figure 21: Proper moisture content of pumice-concrete

Heed the following points in preparing your pumice concrete:

  • Use only clean pumice
  • Saturate the pumice with water prior to mixing
  • Use only new cement
  • First mix the presaturated (soil-moist) pumice with cement; then add water and mix thoroughly to obtain a moldable mix
  • Compact the mixture well, but not excessively
  • Keep precast building members out of the sun and cover them with, say, wet cement bags to keep them from cracking
  • Keep building members out of the rain
  • Let pumice bricks, blocks, planks and panels dry for at least 28 days, or one month, prior to use
  • Stack building members on a level base
  • Handle them carefully to avoid breaking off their edges
  • Remember that pumice building materials can also be made with lime instead of cement

3.1.1 Making building blocks from pumice and lime

Building blocks can be made of natural pumice and lime. Indeed, such blocks used to be quite common. However, careful consideration must be given to the characteristics of the lime.

In the first place, use only hydraulic—or better—eminently hydraulic lime. Dolomitic or magnesium lime, i.e. lime with a somewhat grey colour, is preferable to fat lime, i.e. chalk-coloured lime, for making good pumice. Lime blocks, thanks mainly to the fact that the grey types, as the name implies, contain more magnesium, which reacts with the silica fraction give the finished product superior strength properties. On the other hand, whatever lime is used should contain as little salt as possible, particularly in the form of sulfuric acid, because salt causes efflorescence and detracts from the blocks’ mechanical strength.

To obtain pumice-lime blocks with strength values exceeding 20 kg/cm²:

– the exact chemical composition of the lime and all pumice materials under consideration should be ascertained by way of careful chemical analysis, and

– sample blocks and compression strength test specimens should be prepared.

In general, the following mixing ratios are recommended:

1 m³ pumice (slightly moist, but not dripping wet)
150 kg hydraulic lime gauging water as necessary or
3 m³ pumice (slightly moist, but not dripping wet)
250 kg hydraulic lime
100 kg Portland cement gauging water as necessary

The latter batch should yield about 1000 pumice-concrete solid bricks measuring 25 — 12 — 10 cm and displaying a compression strength of roughly 25 kg/cm² after approximately 3 months’ curing time.

It is extremely important to realize and act on the fact that pumice-lime bricks need a much longer curing time than do pumice-cement bricks. They should be allowed to cure a good three to six months to develop adequate stability and compressive strength prior to transportation and use.

Accordingly, it’s better to make solid bricks than cavity blocks out of pumice-lime mixes, since the thin walls of the latter are much more susceptible to breaking and therefore require more caution in their manufacture and use.

What can you make with pumice?

Once the pumice-concrete mixture consisting of pumice, cement and water has been properly prepared, it can be poured into various moulds to produce different kinds of wall members, e.g. pumice-concrete tiles/panels and reinforced pumice-concrete hollow-core planks (cf. Fig. 22).

Pumice concrete should not be used for making building members that will be exposed to heavy wear and tear, e.g. stairs, nor is it suitable for building members that are liable to have constant contact with moisture.

3.2.1 Pumice concrete

Lightweight pumice concrete is made in the same manner as normal-weight concrete, except that natural pumice takes the place of sand and gravel. To make pumice concrete from the basic materials, pumice, cement and water, follow these steps:

  •  The first step after the raw pumice is delivered to the intended production site is to remove any humus and other impurities by screening or desilting as necessary.
  •  The second step is to establish the particle-size spectrum of the pumice material. To obtain a good pumice concrete, the particle -size distribution should be about 1-16 mm, i.e. the pumice should have roughly 40 per cent particles measuring 1 – 3 mm in diameter, 25 per cent particles measuring 3 -7 mm in diameter and 35 per cent particles measuring 7-16 mm in diameter.

Pumice P24.GIF
Figure 22: Four pumice-concrete building members

If the particle-size distribution of the raw material does not approximately correspond to the above, it will have to be screened as shown in Figure 23.

Frequently, it will suffice to screen off the particles that are larger than 16 mm, perhaps replacing them with sand.

Pumice P25A.GIF
Figure 23: Screening the raw material

  •  The third step is to add cement and water to the pumice gravel to produce pumice concrete, preferably with the aid of an electric or diesel-powered mixer. If none is available, the concrete can be mixed just as well with a shovel on a clean base or in some kind of big tub (Fig. 24).

Pumice P25B.GIF
Figure 24: Hand-mixing system

How much cement and water are needed depends greatly on the physical condition of the pumice material, especially its inherent moisture and particle-size distribution. As a rule of thumb though, four parts pumice to one part cement and one part water is about right (Fig. 25).

Pumice P25C.GIF
Figure 25: Volume indication of quantities

Pumice concrete should be soil-moist, i.e. it should have no excess water. The moisture level is right if the mould surrounding the concrete can be removed immediately after compacting without having the shaped piece fall apart (Fig. 26).

Pumice P26A.GIF
Figure 26: Immediate removal of forms possible

3.2.2 Pumice concrete solid bricks/blocks

The least complicated kind of wall member for do-it-your-self production by people with little or no handicraft experience is the simple solid pumice brick (Fig. 27). The dimensions can be chosen at will, but adhering to a standard commercial brick format is recommended. If the bricks are to be used for repairing existing walls, they naturally should be of the same size as the bricks or blocks in the old masonry.

Pumice P26B.GIF
Figure 27: Pumice-concrete solid brick.

Elementary-type pumice-concrete bricks are best suited for use in filling out concrete skeleton structures, but are also good for putting up self-supporting walls. Particularly in areas where no loam or clay is found, pumice bricks serve well as alternative wall-building members, assuming, of course, that natural pumice is available (Fig. 28).

The production of pumice concrete solid blocks measuring 49 — 24 — 15 cm is described below. Such blocks are easy to make in a self-help situation.

First, make a simple wooden mould with inside dimensions corresponding to the desired block format (Fig. 29). Normal, smoothly planed boards or square timbers make good box-mould building material. In making the box mould, be sure that it will be easy to remove from the freshly compacted block, i.e. that it is either easy to take apart and put back together or has such smooth inside faces that the block slips out easily.

Pumice P27.GIF
Figure 29: Wooden mould for pumice-concrete solid brick, including board

Place the box mould on a smooth, level base, or better yet on a smooth backing board. Try to have a large number of such boards on hand, depending on how many blocks are to be produced in a certain length of time.

Pour the pumice concrete into the mould(s) and compact it by tamping with a wooden or iron compactor (Figs. 30a and 30b). Smooth off the top with a lath (strike board). If the concrete is soil-moist, the box mould can be removed immediately after the concrete has been compacted (Figs. 30c and 30d). Clean it with water for immediate reuse. If the pumice concrete mixture is right, the freshly compacted block, the so-called “green compact” will not lose its shape, i.e. crumble or sag.

Pumice P28.GIF
Figure 30: Forming pumice-concrete solid bricks

Give the green blocks four or five days to harden before stacking or otherwise handling them. Subsequently, they will require another four days of hardening before they can be transported. All in all, a curing time of 28 days, i.e. one month, is required before they can be placed.

The dimensions 50 — 25 — 12 cm and 30 — 24 — 11.5 cm make a good choice for commercial-scale production of handstruck blocks/bricks, because one and the same kind of block/brick can be used for putting up a 30 cm thick wall, a 24 cm thick wall or an 11.5 cm thick wall.

3.2.3 Pumice concrete cavity blocks

With a little practice and skill, pumice concrete cavity blocks are also easy to make in small quantities. The size of the wooden mould is more or less a question of personal preference, but a 49 — 24 — 15 cm format with two cavities is recommended (Fig. 31). With a view to facilitating placement of the blocks, it’s advisable to leave the cavities open at one end only. That way, the mortar is easier to distribute around the supporting surface without having it fall into the cavities (Fig. 32). Since the blocks are supposed to be removed from the moulds immediately after they are compacted (so that the wooden moulds are immediately available for reuse), the inside of the moulds should be made as smooth as possible. Some sort of sheet metal lining serves exceptionally well. Considering the handmade nature of the finished blocks, either round plastic tubing or blocks of wood would be the best choice for use as cores for forming the cavities, since both are easy to twist out of the green product without damaging the cavities.

Pumice P29A.GIF
Figure 31: Wooden mold for two-cavity blocks

The production of concrete cavity blocks requires careful work to avoid damaging the corners and edges of the blocks when the moulds are removed. The main things to watch for are that the pumice concrete is neither too dry nor too wet and that it’s carefully compacted.

Pumice P29B.GIF
Figure 32: Spreading mortar on a cavity block

  • Follow this procedure for making two-cavity pumice-concrete blocks:
  • Place the wooden mold on a support (wooden board)
  • Cover the bottom of the mould with about 2 cm of pumice concrete (Fig. 33a)
  • Put the core pattern (for plastic tubes or wooden blocks) on the mould (Fig. 33b)
  • Insert the tubes or blocks for the cavities
  • Remove the pattern
  • Fill the remainder of the mould with pumice concrete and compact it well (Figs. 33c and 33d)
  • Then, slowly and carefully pull the plastic tubes or wooden blocks out of the mould and remove the mould itself (Fig. 33e)

Pumice P30.GIF
Figure 33: Forming pumice-concrete two-cavity blocks

Leave the block on the board to dry for 4 – 5 days. Then stack the blocks to harden for another 4 days. After a total of 28 days, the blocks will have cured sufficiently for transportation and use. Handle the blocks with care, because they break more easily than solid blocks.

If you wish to produce large numbers of cavity blocks, use either steel molds instead of wooden moulds or, better, a simple hand-operated mechanical press that compacts the blocks and ejects them from the moulds.

Pumice P32A.GIF
Figure 36: Filling the corners with concrete and reinforcing bars

Since cavity blocks have relatively thin walls (approx. 2 – 3 cm), the pumice concrete should have a maximum particle size of about 10 mm, i.e. any fraction above 10 mm will have to be screened out of the pumice gravel prior to mixing the concrete. Screening can be accomplished using simple wire screens with mesh sizes of 10 mm (approx. 3/8″) and 7 mm (approx. 1/4″). The recommended mixing ratio reads:

  • 2 parts pumice, 1-6 mm in diameter
  • 2 parts pumice, 6 -10 mm in diameter 1 part (Portland) cement

The advantage of cavity blocks is that they weigh less than solid blocks/bricks, which also means that less pumice concrete (and, hence, less cement) is consumed in making enough blocks for a wall of a given size. An additional advantage is that the cavities situated at the corners of the house can be filled with concrete and reinforcing bars to yield a strong framework’ which can be very important in areas subject to earthquakes (Fig. 36). To do so, ram the reinforcing bar (or some other round tool) through the block bottoms to get wall-length cavities at the corners (Fig. 37).

Pumice P32B.GIF
Figure 37

Pumice concrete cavity blocks are useful above all else for filling out skeleton structures, but they are also suitable for making load-bearing walls. Different house-building systems based on cavity blocks are discussed in Chapter 4.3.

3.2.4 Pumice wall panels

How self-help builders with little or no training can use pumice to make simple wall panels measuring 100 — 50 — 5 cm or 100 — 50 — 7 cm is described below. Such panels can be used in any of several time-tested special-purpose house-building systems.

The main merit of the relatively small format is that it makes the panels relatively light and accordingly easy to produce, haul and handle—just right for do-it-yourselfers. A panel width of 50 cm and length of 100 cm combine well for a 2.00-m wall height, and openings for doors and windows can be made by simply leaving out a number of panels at the appropriate places.

To make such pumice-concrete panels, proceed as follows:

Make a simple wooden box mould out of 5-8 cm thick boards. If a large number of panels are needed, it would be a good idea to make several identical moulds. That way, the panels can be stacked to save space. The long sides of the panels are supposed to be grooved. To make the grooves, use strips of wooden trim or plastic tubing (Fig. 38a). Later on, when the panels are being placed, the grooves must be filled with mortar to obtain strong joints. For details on wall construction with pumice-concrete panels, refer to Chapter 4.4.

Pumice P33.GIF
Figure 38: Forming pumice-concrete panels

The panel-making area must be absolutely level. Each panel should have its own support made of smooth sheet-metal or wood. If nothing else is available, smooth paper or plastic sheeting can be laid out under each mould/panel, as long as the ground is perfectly level.

Considering the size of the panel, it would be a good idea, but not absolutely necessary, to include some form of iron reinforcement consisting of, say, a lattice arrangement of 10 mm (3/8″) reinforcing bars sized to match the panels’ dimensions. Any panel that will be subject to bending stress (sag), though, should have at least two such bars running lengthwise with several bends/curves (Fig. 38b).

Pumice P34.GIF
Figure 39: Mould for hollow-core planks

For poring the panels, prepare a soil-moist pumice-gravel concrete, consisting of four parts pumice gravel to one part cement, and fill the wooden frame with it as described in Chapter 3.2.1. Place the reinforcing lattice such that it “floats” at the centre of the panel; smooth the surface of the panel with a strike board or trowel (Figs. 38c and 38d). Leave the panels on the ground to set and harden for about five days, after which they can be handle and stacked. Then give them 25 days to cure prior to transportation and placement. In loading the panels for transportation, be sure to protect them against impact and bending, i.e. it’s better to arrange them in an upright position instead of laying them flat.

If the floor in question will not be subject to heavy loads, reinforced pumice-concrete cavity planks can be used in place of the reinforced hollow girders (cf. Fig. 40, Chp. 3.2.5). Planks up to 10 cm thick, however, can only be used to span not more than than 3.0 m. In homes of simple construction, however, such reinforced planks can serve well, as long as careful attention is given to reinforcement, installation and handling, in addition to clarification of the acceptable span width with the aid of a stress analyst (structural engineer).

Pumice P35.GIF
Figure 40: Forming pumice-concrete hollow-core planks

The prime use for such simple building panels is for filling in skeleton structures, although they can just as well be used for repairing existing walls and building new houses. Consider for example the house described in Chapter 4.4. It consists of a skeleton made of channel-section steel into which the panels are inserted. An alternative example consists of a load-bearing wooden framework and inserted panels.

Pumice P36.GIF
Figure 40 (2)


Pumice P37.GIF
Figure 40 (3)

3.2.5 Reinforced pumice-concrete hollow -core planks

Compared to the simple type of panel described in the preceding chapter, it takes somewhat more skill, tools and technical equipment to produce reinforced pumice-concrete hollow-core planks. Consequently, this approach is more suitable for collective self-help building projects than for individual homes. Since easy handling of building members is an important criterion in connection with self-help building projects, care should be taken to avoid making excessively large planks that could not be carried by hand. A maximum length of 250 cm and a maximum width of 50 cm are recommended. The planks used in the model homes discussed in Chapter 4.5 measure 220 — 50 — 10 cm. Planks of that size are just small enough to be carried and placed by four workers.

A relatively large area is needed for producing hollow-core planks. Especially the casting area has to be absolutely level, hard-wearing and easy to clean. The plank moulds should be made of solid wood, because they will have to be used repeatedly (Fig. 39). Longitudinal cavities are necessary to save weight. To make them, place plastic tubes or steel pipes in the moulds and pull them out after the planks have been compacted. To cast the planks, place the fully assembled wooden moulds on a perfectly smooth and level floor panel or on ground covered with plastic sheeting. Alternatively, the floor panel can be coated with used oil before the moulds are filled. Soil-moist pumice concrete prepared as described in Chapter 3.2.1 should be used for making the planks.

First, pour a 2 or 3 cm thick layer of pumice concrete into the properly prepared mould and carefully tamp it with a broad hand-held compactor. Even better results can be achieved with a roller, e.g. a steel pipe filled with concrete (Figs., 40a and 40b). Try to get the surface as level as possible. Next, insert the pipes or tubing through the holes in the short ends of the moulds (Fig. 40 c). Place thin reinforcing rods (do not forget to have them ready) between the core tubes/ pipes (Fig. 40d). Now, fill out the interspaces with a second layer of pumice concrete that just barely covers the pipes/tubes. Again, carefully tamp the concrete with a broad compactor (or use a roller). Then, pour the third and last layer of pumice concrete, compact it, and strike off the surface with a straightedge lath, subsequently smoothing it over with a trowel (Figs. 40e and 40f). Now, carefully twist the pipes/tubes out of the mould and remove the mould from the green plank. Leave the planks on their bases to set and harden for about seven days. After that, they will be durable enough for lifting and carrying. They must be transported in an upright position (as opposed to lying flat) and will require a total of 28 days curing prior to use (Fig. 41). With a view to achieving uniform quality, the planks should, if possible, be prepared in series in a small production installation. That, in turn’ will require the availability of several identical moulds and pumice concrete of uniform quality.

Reinforced pumice-concrete hollow-core planks serve well as filler members in various types of frame construction. A simple model house made of load-bearing hollow-core planks is described in Chapter 4.5.

3.2.6 Special-purpose pumice-concrete building members and their applications

Channel blocks can be very useful (Fig. 42) as form blocks for peripheral tie beams, as lintels for doors and windows and as filler blocks for anchoring steel door hinges, wall ties, etc. (Fig. 43).

Pumice P38.GIF
Figure 43: Channel form block in a tie-beam configuration

Channel blocks are made in much the same manner as cavity blocks, except that the core (block of wood) is not placed at the centre, but flush with one side of the mould. The walls of channel blocks should be at least 3 or 4 cm thick to make them strong enough to cope with the pressures that arise in connection with pouring and compacting the pumice concrete.

Closed, square hollow blocks serve primarily as form blocks for columns and as chimney blocks (Fig. 44). The blocks must be carefully aligned during placement, or there will be danger that the concrete could push them out of line, resulting in a crooked column. Such blocks serve well as chimney blocks if the clear cross section measures at least 10 — 10 cm and the walls are at least 5 cm thick.

Pumice P39A.GIF
Figure 44: Chimmey block

Naturally, attention should be paid to dimensional accuracy in fabricating the blocks in order to obtain straight, well -functioning chimneys.

Pumice P39B.GIF
Figure 45: Masonry corner with channel block serving as support fromwork

Fine-grained pumice concrete can also be used to make diverse kinds of vent blocks that provide through-wall ventilation without letting in sizable vermin or other uninvited guests (Fig. 46). Such blocks also serve as ornaments and in the construction of ventilated storerooms. They are made in a manner similar to that used for producing cavity blocks, as described in Chapter 3.2.3. However, we recommend not trying to make blocks of very complicated shape, because pumice blocks are never as smooth as those made of normal-weight concrete.

Pumice P39C.GIF
Figure 46: Vent block

Yet another application for pumice-concrete blocks are intermediate floors. So-called pumice-concrete “hollow floor fillers” can be used in constructing ribbed floors (Fig. 47), e.g. when there is a shortage of form – work material, since such floors consist exclusively of prefabricated members.

The load-bearing beams, i.e. “lattice girders with concrete flanges” are suspended between the walls in a carefully aligned arrangement, with spacing to accommodate the hollow floor fillers. Then the fillers are placed side by side on the concrete flanges of the lattice girders. Check the visible under face, the seating, the end blocks, etc. and install any supplementary reinforcement that may be considered necessary. After that, place a 5 cm-thick layer of pumice concrete over the fillers. The main function of the pumice in such floors is to minimize concrete consumption and reduce the weight burden in the tensioned zones of the floor.

With the requisite accuracy of static analysis, orderly installation and a small-scale industrial production mode, self-help groups can manufacture so-called “beam floors with pumice-concrete hollow-core plank fillers.” The precast hollow planks should measure about 30 — 30 cm, with a length of 3 – 4 m, and have structural-iron reinforcement in their tension zone. They’re placed side by side then filled with concrete. This yields a very sturdy floor that will carry relatively heavy loads, depending on the span width, reinforcement, and the thickness of the pumice-concrete hollow girders.

This article was excerpted from Building with Pumice (GTZ, 1990, 86 p.). Reposted from Appropedia. © 1990. Open Access.

November 23, 2013 |

The BIQ Building: The world’s first full-scale bioreactive façade

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Energy production from algal photosynthesis isn’t new of course, but with fifteen apartments, The BIQ building is the world’s first full-scale bioreactive façade. BIQ, which stands for Bio Intelligent Quotient, uses heat recovery as its main source of energy, capturing energy not used in photosynthesis from the bioreactor solution. The façade of this building located in Hamburg, Germany, also acts as a natural thermostat: thick algae growth in the summer keeps the sunlight out.

The two south-facing facades are covered in a shell of bioreactors, clear containers that create a controlled environment for an algae farm. Exposed to sunlight, the algae photosynthesize, absorbing CO2 as they grow. Nutrients and CO2 are circulated through the bioreactors to encourage growth. Periodically, the algae are collected and fermented in a nearby biomass plant, then burned to produce electricity.

The technology was created by SSC Strategic Science Consult, which developed the building in collaboration with Arup, a design, engineering and consultancy firm; Colt International, a project management company; and Otto Wulff, a Hamburg construction firm.

Subject to further tests, SSC claim a conversion efficiency (the amount of light hitting the façade converted to energy) of 10 per cent for biogas and 38 per cent for heat—almost 50 per cent in total. That compares to a typical efficiency of about 15 per cent for PV solar. The heat and power from the bioreactors are also supplemented by rooftop solar panels and an underground heat storage system. The building’s creators claim it can meet 100 per cent of its energy needs.

The main barrier to further adoption of the technology is price. Of the €5 million invested in the project by the German government and IBA Hamburg, an international building exhibition, over €1.3 million financed the bioreactors. However, Martin Kerner, Managing Director of SSC, is confident the technology can become competitive. “We need standardization of hardware production to reduce costs,” he says.

Demonstrating the efficiency of the algae building could not only prove a source of sustainable energy production, it could also shape future cities, according to Jan Wurm, Europe Research Leader for Arup. “If we can demonstrate microalgae facades, we can transform the urban environment [and provide] architects with a new source of inspiration.”


By Fionán O’Muircheartaigh. This article originally appeared in Green Futures, the leading magazine on environmental solutions and sustainable futures published by Forum for the Future.

September 16, 2013 |

Building deconstruction and C&D material reuse stores

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Demolished buildingBuilding deconstruction, or “construction in reverse,” is the most effective way to preserve the embodied energy of the materials that comprise the built environment.  Deconstruction is defined as the comprehensive dismantlement of building components, specifically for reuse, resale, recycling and waste management. Compared to traditional demolition in which a structure is torn down as quickly as possible and waste is deposited into commercial landfills, careful consideration is given to deconstruction and waste redirection throughout the entire process. Deconstruction focuses on giving salvageable materials a new life once the building as a whole can no longer continue and addresses the appropriate disposal of waste.

However, the biggest drawback to deconstruction is the extra time and labour required by the process, thereby adding to its upfront premium. To offset this disadvantage compared to traditional demolition, most deconstruction firms are non-profits, thus providing a tax deduction to the property owner for the appraised value of any materials salvaged for reuse. Deconstruction Management Inc. (DMI) is a for-profit entity that provides on-site management of deconstruction contractors and facilitates the reuse, resale and redirection of salvageable materials. In a recent project, we successfully returned 70 per cent of the proceeds received on the sale of reclaimed materials back to the property owner (a non-profit with no incentive to receive a tax deduction for donations).

One of the industry’s primary goals is to identify potential consumers of reclaimed building materials that are prepared to pay cash to give a building component a new home. One such solution to date is the Habitat for Humanity’s ReStore project where local Habitat for Humanity affiliates own and operate a retail store that sells building materials reclaimed from deconstruction projects or donated by contractors. These stores have been a valuable component of the independent affiliates to offset their reduced operating cash flows due to the recent economic downturn. There are many other local outlets for the resale of reclaimed building materials, most of which are non-profit organizations that not only sell, but will accept donated materials in good working condition in exchange for a tax deduction.

In her 2009 report, Dr. Rachel Weber concludes a study on the demand for a large scale C&D material reuse store in the greater Chicago are with the following statement:

A growing ecological awareness is influencing consumption patterns… buying used has the potential to save not only consumers money but also building owners and developers who will likely have to pay higher fees for dumping debris in landfill in the near future. This is why building material reuse stores across the country are reporting increased sales despite the current recession. Moreover, on the labour market side, deconstruction is becoming an oft-mentioned “green job” that has the potential to replace some of the manufacturing jobs that have been lost, while offering a path to additional opportunities in the construction industry and the skilled trades.


Mark Rabkin oversees the marketing and administrative functions of Deconstruction Management, Inc., the first, dedicated, for-profit deconstruction management firm in the country. Mark is a leader in the advocacy of sustainable building strategies both locally and nationally, serving as the volunteer Director of Advocacy for the Northeast Ohio Chapter of the United States Green Building Council.

Reposted from Construction Law Musings under a Creative Commons BY-NC-ND license.

image: Tristan Smith (Creative Commons BY-NC-SA)

June 8, 2013 |
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