Green Building Discussion

 

Techniques for Building With Earth

Also see the Clay-Wood Chip discussion. Discussion participants:

All postings are the opinion of the writer, and BuildingGreen can take no responsibility for their accuracy or appropriateness.

Buzz Burrell describes some systems

From: Buzz Burrell
Sent: Tuesday, December 03, 1996 12:07 PM

Thanks for your comments; since he is a well-regarded person, I am glad to know Robert LaPorte exhibits much better behavior than I experienced. I guess he had a bad day 2 years ago - maybe like I was must have been having when I went out on a limb and described my negative experiences in a public forum.

>There are many paths, as you have noted, and the answer I have for myself which >i offer to you about the labor intensity of straw-clay and other similar >systems is that if we built only what we needed (very small) then we would have >time to hand-craft our dwellings out of more natural materials (and R value >would be less important, if the wall area is very small). I think this is >behind the work of the cob folks out in Oregon. So, not for everyone, but >maybe for some.

Well said! And besides the ecological aspects, there is the *satisfaction* factor - rather than supervising the building of a trophy house, I've always thought it would be really nice to handbuild a house out of rock, spending whatever time as it took. Just the thought of carefully examining each and every rock sounds wonderfull to me.

Bill C also responded:

>It (strawclay) still sounds better to me than making adobe bricks or rammed earth. But I >haven't done the hands-on with them yet either.

Actually, I was considering them both when I took that fabled workshop. One hour of gathering, shoveling, sifting, sorting, mixing, rolling, carrying, placing, and then beating on strawclay convinced me to use a Compressed Earth Block system. I thought I wanted to do the cheapest system possible, but I instantly decided to spend some money instead (with clear feedback from my body).

C.E.B. is sometimes just called Rammed Earth, and sometimes called Adobe, in order to avoid lengthy explanations and because they are very similar. Quick clarification:

Adobe - Sun dried mud. Famous, very common in SW, very historical. Blocks can be any size, but are commonly 10" x 14" x 3.5". and are stacked with a mud motar. Nowadays are often made with 4 - 10% asphalt for stabilization (weather resistance).

Rammed Earth - Like it sounds: compressing dirt under pressure into a structural form. Rammed Earth usually refers to a monolithic wall form, like a concrete pour, into which earth is tamped either by hand or with a hydraulic ram. Earth used is damp, never wet (amoung other differences from adobe).

CEB - Great pressure is used to compress earth into blocks. Thus, it like using Rammed Earth methods to create an Adobe block. Many sizes, but 8" x 12" x 4" is most common. Does not require motar joints. Another cool thing is you can (if the soil is right) excavate your foundation, and then use that same soil to build your walls! (Quantities used can be the same). Overseas (see below) people use lever-action presses, while in the states, people rent powerfull hydralic presses.

Disadvantage is same as adobe: unlike strawclay, there is minimal insulation. Advantage: my walls (including bond beam) were done in 12 working days.

>>Shortly afterward I (Buzz) >>went to India where I investigated various natural building methods in a >>country that prides itself on low-capital home-grown technologies.

>I'd (Bill) be interested in hearing what you felt were the most exportable building >methods over there. (I doubt many americans will want to build dung huts, >for instance). It seemed to me that the majority of the buildings that I saw >were brick masonry with plaster (this was in the New Delhi area)

Quite right. Brick and concrete is everywhere (as in about 90% of the world, wood is never a primary material).

What I found was Compressed Earth Block being tested in all parts of the country. I never heard mentioned strawbale or strawclay; adobe is rare but still being used in some remote locations. I found CEB machines made in France, California, and Australia in use, and now they are manufacturing one specifically for village use in India.

You may have heard of a company called Development Alternatives; based in Delhi, it is the most advanced alt-tech organization I've ever encountered, the RMI of India if you will. Additionally, the real international earth-building experts are the French; CRATerre has built amazing projects all over the world (except in NA).

CEB works great in India because it isn't all that cold, so insulation is less a requirement, and the comfort standards are broader. They just render the walls with a wetter version of the same earth mix, and then either do a earth, concrete, or tile floor, and the same for the roof. Seeing a CEB roof is quite impressive; reminded me how very little I know about building.

Take Care!

Buzz Burrell Geneva Development Corporation Boulder, CO

Top of file

Mike O'Brien on life in Ethiopia

From: Mike O'Brien
Sent: Tuesday, December 03, 1996 1:16 PM

Ah, your description of CEB brought back memories of using a cinva-ram press (made in South Africa, as I recall) with a manual written in French--thank goodness for those high school French classes I thought were so booooring--to build a house in Ethiopia. We were up against wattle-and-daub, usually consisting of split eucalyptus wattle and whatever-mud daub, finished with whitewash inside and out. Though rammed blocks were better, w & d was easier--nothing had to be square, and no cement stabilizer was needed--very expensive stuff in Ethiopia. That was 30 years ago--good to hear CEB still being used and improved.

What I mostly wished for then was a roof other than corrugated metal--when it rained you literally couldn't hear yourself think--we used to stop classes and just stand around with our mouths open watching rivers of water coming off the eaves of the school. The metal roof on our house did make for a good alarm clock when the ravens landed on it every morning at 5:30 AM!

Mike

O'Brien & Associates Environmental Building Consultants Portland General Electric Earth Smart program Earth-Wise Builders Association obrien@hevanet.com

Top of file

Hal Levin on the CINVA system

From: Hal Levin
Sent: Tuesday, December 03, 1996 2:58 PM

While working as a Peace Corps Volunteer architect, I designed some 18 schools, many of which were built with what Buzz is calling Compressed Earth Block (CEB) with the additional of between 7 and 16% cement to the mix to stabilize it. The amount of cement was determined by some simple, on-site tests of the available soil - the ratio of fines to coarse particles, or clay to sand, if you prefer. The pressure was applied in a steel press called a CINVA-ram. CINVA was a national housing agency in Bogota. The press was manufactured at that time in Bucaramanga, Colombia, by a company started by a limited-profit corporation of the Rockefeller Foundation. The presses were heavy, but they could be transported by horse or mule to the very remote, often high Andes sites of many of the schools. The cement would also be so transported. The resulting blocks were far stronger than fired brick at a fraction of the energy or cash cost. A bond-beam was poured around the top of the wall. I had one school under construction in a village hit by a significant earthquake that levelled the homes in the village. The bond beam had not been formed or poured, nor had the corner reinforced concrete posts. Yet the walls, basically free-standing, unreinforced, unbraced as they were, survived in tact. It was pretty amazing to me. Did we really need the posts and bond beams? I don't know.

These schools were labor intensive, but they were not cash intensive. The communities where they were built were quite poor, usually living at a subsistence level or barely above. My typical budget was about US$300. Hardware and roofing were the main purchases. Community action groups did the construction on community work days and they also raised money in some of the more urban sites by holding dances and raffles, etc.

Other stabilized earth products used asphaltic emulsions, a process also used successfully to stabilize roads made by churning up the soil and adding the stabilizer before rolling the road smooth with appropriate drainage slopes.

The cement does require external energy inputs. My view is that if something is going to last as long as it should given the amount of labor invested, it justifies some energy consumption. Hopefully, someday, there will be a way to create cement using renewable energy that will be commercially viable. Perhaps it is being done already in more isolated places or where energy costs justify more investment in renewable sources today.

Hal Levin email: hlevin@cruzio.com 2548 Empire Grade, Santa Cruz, CA 95060 Tel. 408 425 3946 Fax 408 426 6522

Top of file

Buzz Burrell tries the hydraulic version

From: Buzz Burrell Sent: Tuesday, December 03, 1996 11:14 PM

Good CINVA stories. Interesting that two people on the List have had direct personal experiences with this classic app-tech tool, seemingly from a by-gone era. I've never seen one myself (except pictures in old Whole Earth Catalogs), but the presses being made in India are improved versions of the same thing.

BTW, the ram I used (rented) cost about $25k new and puts out 4-5 blocks per minute by pressing a button. Dirt is put in the hopper with a backhoe. If you tried to amortize the cost of just those two pieces of equipment, one would have to make quite a few blocks before it would be cheaper than a CINVA ram with a bunch of strong-backed people.

Take Care!

Buzz Burrell Boulder, CO