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Ways to Make Adobe Bricks |
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Q: What do you know about baked or fired adobe brick? Lots of energy is needed to fire the bricks. The Mexican technique is to stack the adobes to be fired and then build a mortarless vault of adobe over them. A flatbed truckload of firewood is ignited at one end and a simple chimney at the other end gets the fire roaring through the adobes for perhaps three days. After cooling the adobes are shipped north. The adobes which formed the vault are then stacked to be the fired adobes in the next cycle. An interesting observation of this process is that the outer layer of vaulted adobes never vitrify more than the inner quarter-inch if even that. It is only the interior stack that vitrifies. Nader Kahlili has a book on fired houses, but I think that the Mexican experience shows that it would be nearly impossible to do that. Meantime, the Mexicans have to keep going farther from their villages to find sufficient firewood for the process. The hills become denuded as was the case in Rome. So most folks don't build the entire home of quemados, just the exterior walls or perhaps the above mentioned wall copings. Add to that the fact that vitrification changes the nature of the adobe bricks ability to transmit heat. It speeds up the thermal diffusivity. That's too bad since it is the sluggishness of adobe that makes it stand out above all other masonry materials as a storage medium for heat especially in the passive solar home. Q: Is there any special treatment or chemical to be used in making adobe? (or just sand and clay and then fired?) A: Sand and clay. Not fired. Just baked in the sun. The largest energy input is solar followed by human metabolic energy. How green can you get? Just a shovel and wheelbarrow, a bucket of water and a simple wooden form. With no wood you can form adobe by hand as in Mali. With no wheelbarrow you can move earth in baskets as did the Anasazi of the Southwest United States, with no shovel you can use a pointed stick as many cultures do worldwide. With no bucket or no water one just waits for it to rain and then makes the mud. Q: My house design has a basement. Foundation, stemwall with insulation, then dig basement, use soil for the adobe bricks. Thought it might be easier to purchase bricks if price is reasonable. A: Your idea of making adobes from the basement excavation is excellent. With a little asking around, you might find someone who will make adobes for $.25 to $.40. With a pile of loose dirt, all that is needed is a wheelbarrow, shovel, water, and a form to make four adobes at a time. Once people get the hang of it, two can produce about 500 adobes per day. The secret is not to mix. If the excavated soil is the right blend of clay and sand (30% / 70%) water can be poured into a small area of the pile and when it soaks in, just shovel it into the wheelbarrow. That plus the action of pouring the mud out of the barrow and into the form is all the mixing that is needed. If the soil needs sand or clay, let the excavator machine blend it dry. Q: Where can I get ahold of a Cinva ram and for how much? A: They are being built somewhere in Africa. Cost and location unknown. We have a Cinva Ram here at Northern Community College in El Rito, NM. Come and try it. It has convinced a number of people to look for a different way to make adobes. I personally think two guys with a loose pile of dirt, a wheelbarrow, a 55-gallon drum of water and a form that makes four adobes at a time can produce adobes faster than a Cinva Ram. Most Cinvas make an adobe about 8 or 10 inches long, 5 inches wide and 5 inches tall. Most codes require a wall at least 10 inches wide so it takes a lot of CR bricks to make a wall. Standard New Mexico adobes are 10x14x4. Q: I am a 14 year old boy and I live in a rural area. I want to build a small house for "self-sustained" living. I made 16 bricks to start off with and they seem to be drying fine. However I spent forever mixing them. I am very happy to see your suggestion about "not mixing" that will save a lot of work. My main question is this: where I am we have "quack grass" all over the place and it's not perfectly level. Can I just place my form over the mowed grass and start throwing it (the adobe) in, or do I need a tarp to put it on? Thank you very much and my next web stop is the adobe message board which I started out to find! A: You are off on a wonderful enterprise. I was making models of adobe homes when I was 10 and 11. Sometime around age 13 I started making full sized adobes in the back yard. My dad got mad when it killed the grass but after a while he mellowed when he realized that he did not have to mow it any longer! Most any type of construction is hard work, and adobe probably tops the list. But the harder you work at it the more it will mean to you when you are done. Making the adobes is usually the hardest part of adobe homebuilding. Try making your adobes right on top of the quack grass. The first time around the grass imbedded in the bottom of the adobes might make it hard to lift the adobes or the bottom might be pulled off. Sooner or later, the grass will quit being a problem if it is one in the beginning. The tarp will make the adobe lift up for sure but they will take longer to dry. A lot of moisture in the adobes is lost downward into the ground. The wicking action of the ground is equal to the drying action of sun and wind at the top. Q: What are some of the potential disadvantages of using a compressed block machine to make adobes, and how would these blocks handle a warm humid summer like we have here in Wisconsin? A: The blocks should do okay in your climate. Like any wall material, they need to be kept dry after manufacture, as the wall goes up, and for the life of the wall. Since the blocks are made with high compression, sometimes when they get wet, they "blossom" or expand as unresolved internal forces realign themselves. Keep them dry and you will do fine. One reason that just a slurry is used instead of thick mortar is that there would be enough moisture in regular mortar to cause blossoming due to the uptake of the moisture into the blocks. Some blocks have grooves and they go together without any mortar at all. C: Something positive could also be said about CEBs like how they provide the same benefits as adobe. CEBs also allow people in wetter climates to produce blocks, and lots of them, because the blocks do not have to dry (Which works well in the SW but not as well here). Like any building material, CEBs must be protected from moisture, however, they can be stabilized with portland or lime. I have had no problem laying CEBs in mortar or a slurry. The only time I have seen the "blossoming" effect is when the blocks were drenched or submerged in water. So, when you say moisture I think it is important to be specific as to moisture as vapor (humidity) or moisture as liquid (rain, snow, broken pipe, etc.) Q: Where do you find details about making bricks, you said 2 people with a 4 brick mold could make 500 bricks a day. Can you take the mold away as soon as the mud is put in and leveled? A: You just have to fool around with the amount of water in your brick mix to get it stiff enough to stand up when the mold is pulled. And just plastic enough to work it into the mold without too much trouble. Invest an hour or two in fooling around and you will have the right blend for your soil. Also if there is too much clay, the bricks crack. You can experiment with adding sand, small gravel, and some straw to keep it from cracking. Q: I am seeking a source in central Texas (or anywhere reasonably close) for stabilized adobes. I helped a relative build a small adobe house in Alpine, and saw his own 2000+ sq ft house near Marathon, and an adobe home is the only way for me to go. I don't think I'll ever get the combination of time, materials, and weather required to build my own blocks like my relative did, so a source is desperately wanted! A: (Neal) Garten Gerdes in Burnet has equipment (lay down machines et al) but has never produced commercially. The adobe he has made and used on his property is very nice and uses the "fines" from the processing of limestone for road base (also sold and used as agricultural lime). His mix (roughly 70% fines, 30% caliche and 3% AE for stabilization) is very similar to that used at the Adobe Patch in La Luz, NM back in the 70s. It makes a very nice block. The material is readily available since there are rock crushing plants all along IH35 through central Texas. If you want to do it the old fashion way, I'll help you build some forms and get a mix put together. I also know of a form system called the Mold-Master here in Austin that might be available that would be an alternative to regular ladder forms. Not necessarily better, just different. If you only need 2-3k adobes, you could probably knock it out in a summer of weekends or hire some labor to get it done faster. Having a flat space to lay the adobes out and cure them is a necessity too. A: We have a very old CinvaRam here on the El Rito Campus of Northern New Mexico College in case you want to experiment with one before you buy. A number of us are not convinced that the press speeds things up especially if the soil has to be blended to work. Q: I wonder if you can advise me regarding some trouble I'm having with my experimental adobes sticking to the molds when I try to pull them. Can I use any oil? I brushed the molds with used cooking oil but they still stuck A: My best guess is that the adobes have a high clay content. 30% clay and 70% sand gives the strongest bricks but higher clay content gives more water resistance in a wall that is not protected from rain or other moisture sources. At those higher clay levels the adobe bricks will usually crack unless they have straw added to control it. I did not fool with oil as it was one more thing to have on the work site. My technique was to thoroughly soak the wooden form in water before the first bricks. The mud needs to be stiff enough to be able to lift off the form right away. With a 55-gallon drum handy or a bucket and rag it can be quickly cleaned or wet. Once my system was going and there was a low enough clay content so that the bricks did not stick, the form seemed to stay wet enough as it took up moisture from each brick. Then I would only clean it off if a bunch of mud stuck in a corner. The addition of cement will not make the bricks swell as far as I know. However, it might make the bricks a bit more sticky. Later, when I had enough forms to make 90 adobes per evening, I made a much slurpier mix and let the adobe sit overnight before pulling the forms. The forms nearly always came clean enough so that I did not have to clean them. Just keep fooling around as each soil and mix has its own personality. Sooner or later you will find the combination that works on your soil. Q : We are trying to secure funding to get a CEB machine to Canada. We need to know if the CEB will withstand a Canadian climate (western Canada at this point) and what mixture is in the block is the main question we are being asked. A: The real question is can anything, including humans, withstand a Western Canadian climate. We are down here in sunny New Mexico where it was a balmy negative 12 Celsius at dawn this morning. Human powered CEB machines are priced around $90US in parts of Africa. Engine powered hydraulic units made in the USA are a bit more pricey. Best blocks will be around 30% clay and 70% sand. There are many variations including silt and a bit of organic matter that can be tolerated in a CEB. It is just a matter of fooling around with perhaps some lab work included to determine the best ratios. If you can get a block out of your soil without having to modify it, then even if it does not give the highest lab test ratings for compressibility or modulus or rupture then it is the best block. Any sort of wall material in Canada needs to be protected from moisture moving up from the ground, moisture penetrating through the exterior wall covering and moisture coming down from the roof system. I am confident that the Canadians have worked out these systems very well. Otherwise their wood houses would mildew and rot, steel houses would rust and fired brick houses would spall apart. A: I think your idea of cutting the trapezoidal bricks is great. We tried to make them in trapezoidal forms and each form locks a person into a narrow range of dome diameter. Cutting them makes more sense and saves building multiple forms. Eventually we settled on rectangular bricks, 7x10x4, and put them together with trapezoidal mud mortar. Q: My Jr. High grandson chose to make a pyramid out of adobe for a school project. Where can we purchase clay to make adobe bricks. We live in KY and have lots of rocks but little if any clay. A: I am assuming that this is a model pyramid. Most craft stores that cater to ceramics hobbyists have clay. There must also be several clay suppliers that sell clay to professional potters in Kentucky especially the closer you get to Berea. Some suppliers will roll it out into a 1/4 or 3/8 sheet. This is perfect to cut into rectangles 1/2 by one-inch or 3/4 by 1-1/2 inch. These make perfect miniature adobes. They do not have to be kiln fired. They will be strong enough air dried just as most pottery is before it is fired. We are delighted to have heard that an adobe house was discovered in Greensburg, KY this summer. It is on the property of a Presbyterian church there and hopefully has been saved. It was being torn down until the adobe discovery was made. Just think, Kentucky has an adobe heritage! |
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Quentin
Wilson and
Associates, specializes in solar adobe design and construction. He grew
up in the South Valley of Albuquerque, New Mexico where he watched adobe
bricks being made. In the fifth grade, he made miniature adobes on cookie
sheets in his mother’s oven in order to construct house models for
a class assignment. By age thirteen he made full-sized adobes in the back
yard and ruined the grass. Later, he traveled a bit, went through the
Army, and graduated eventually from the University of New Mexico with
a major in physics, minors in math, chemistry, and education in 1970.
After teaching high school two years and community college math for three
more, Quentin moved into professional solar adobe construction in 1976
as the Project Manager and Instructor for the Sundwellings Demonstration
Project at Ghost Ranch, Abiquiu, NM. He became a licensed general contractor
in the State of New Mexico in 1982. He has been building homes and teaching
seminars and workshops ever since. In the fall of 1995 he established
and taught the full-time Adobe Construction Program at Northern New Mexico
Community College. His website, 
