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| Q: With my wife, we have recently established a private company in Ethiopia for an investment in eco-cultural lodge in Lake Tana area. As the lodge will be build out of Adobe (similar to some historical construction in Ethiopia), we are considering various construction technique options. Each lodge will be build like a small Ethiopian Orthodox church with wall decorations and paintings. We only use local material (foundations made out of stones, Adobe wall, and thatched roof). The main concern we have in designing is to stabilize the plaster (mud or other material) in order to preserve the wall frescoes we are planning to produce. Do you have any reference on how best to plaster Adobe/mud houses? What material is mostly recommended for interior plastering, keeping in mind that the lodges need to keep a fairly high standard of comfort. A: The same mud that will make adobe bricks makes a good plaster if it is screened through a fine mesh of about 1/8th inch. Exterior Plastering: the rainy season can be very wet and in order to protect wall frescoes on Adobe, stabilization of mud plastering (or other material) is a main concern. Good overhangs of the thatch is the first defense. There must be something that locals use. Around here there is mashed up and fermented mixes of cactus and manure. Some folks rely on lime-based plasters. You can add latex to mud plaster. Careful. If it is so waterproof that it does not breath, then water vapor cannot get out and large chunks of the plaster fall off. Experimentation with appropriate ratios for each soil is required. Make test samples of various ratios and plaster a half-inch thick on a board. Let it dry and set them out to get rained on to see what happens. Moreover, the municipality of Bahar Dar and Amhara regional state in Ethiopia had very recently (19th of June 2005) agreed to lift a ban on mud house construction in urban areas. Yet, they would like to regulate such construction in order to maintain minimum standard for urban development (they don’t want to see slum types of construction in their cities…). Is there any existing standard to which the Municipality and regional government could refer? Bahar Dar enjoys a warm climate with mostly uni-modal rainfall. The wet season can really be wet but it does not last more than 5 months in total. There are links to the older New Mexico adobe code with an update to the newest code coming soon on QuentinWilson.com. Q: Can you make an adobe plaster type mix to cover an old unpainted cement block wall? A: (Kelly) Yes, adobe does adhere pretty well to a cement block wall. Make sure there is enough clay in it to make it sticky, without causing it to crack too much. Q: Should I mix anything else with the clay, and what is best to seal it so as it won't fall apart with the many changes of weather like rain, wind, dry heat, sun here in the Las Vegas Desert climate we have? A: (Kelly) Ideally you want somewhere between 10% and 30% clay, with the rest sand to keep it from shrinking and cracking too much. Sealing it depends partly on how well protected the wall is from the weather by roof eaves. If it is tucked under sufficiently, the straight adobe soil mix will hold up pretty well. Otherwise, you might want to add some Portland cement (maybe 5-10%) to help stabilize it. A: You can certainly plaster over adobe bricks. Some people think that adobe and cement based plasters are not compatible. I used standard cement/lime stucco over adobe homes new and old for 25 years with no problems. I would recommend omitting the use of tar paper or Jumbo Tex between the stucco and the adobes. It is the paper that introduces the barrier that stops the adobes from breathing. Stucco allows moisture and water vapor to pass through. So much has been written that we have ended up with Jumbled Text. A: Adobe plaster sticks to most anything but you may have trouble finding plasterers to do the job. You can do it yourself but it will take some experimenting. First you might tack 15-pound roofing felt over the siding. Jumbo Tex works also and meets the Code. On top of that nail or screw self-furring stucco netting and then plaster onto that. The best mud will have about 30% clay and 70% sand. Chopped straw can be added but is not absolutely necessary. Two coats might do it. To make it last longer, emulsified asphalt can be added in the amount of about 12-ounces per wheelbarrow. Emulsified asphalt comes from the companies which supply highway construction and repair contractors. Another alternative is to use standard cement/lime/sand plaster which will be familiar to most plasterers in your area. The final color coat can be a nice Santa Fe Brown. Q: Last year, I followed and old dream of mine and bought an old adobe house in Guaymas/Mexico. It was built in 1860, out of adobe bricks and mud. The walls are about 28 inches thick and are still in pretty good condition. But it is hard to evaluate as sometimes in the past a cement finish was applied on the outside, thus covering the original finish. Some of that outside skin detached completely from the original adobe and rainwater consequently washed some of the soil out, leaving a void between cement and adobe. One part of the house lost its roof a long time ago, thus showing a lot of wall damage. How can I restore these walls, using modern building materials such as cement if possible at all? Can I chemically bind cement to old adobe earth? What other restoration methods are recommended? A: You are in an enviable position. There are no chemicals that will bond adobe to cement short of spray-on two-part urethane. I don't think that is what you want to do. I recommend that you strip away the cement stucco where it has detached and use repetitive mud plastering to rebuild the missing adobe. Or perhaps parts or whole adobe bricks mortared back into the wall if the depth of the loss is great enough. Then you might re-plaster with cement stucco again. Or mud plaster. If not in Guaymas, somewhere in surrounding villages there has to be a few older folks who have abundant adobe experience. Most of the youngsters have only worked on concrete and clay tile buildings. C: That is exactly what my contractor in Mexico suggested. Using local dirt, ( una mezcla de tierra, agua, semillas de trigo, cal y un poco de yeso para reparar el adobe), and building it up to original size/shape. At that time, we may use DARAWELD C as a binder for the stucco mix. I had the Daraweld dealer stop by and explain how his binder could be used with adobe. Q: My son is building a passive adobe home in Willcox AZ. He is an amateur in adobe taking on this project. They are currently laying the block. He thinks the exterior must have stucco but hates the thought of covering up the beautiful block. His block has the cement added. What is the proper overlay for both the interior and exterior block. His whole purpose of using adobe is for conserving energy and plans to use a wood stove only for heat. A: The New Mexico Code allows adobe to remain unplastered on the exterior or interior. Lots of Arizona homes use exposed adobe. Nearly every Arizona county has its own, if any, adobe code. Plaster is chosen mostly for its look or as a protective or sacrificial coat in areas of greater moisture. A: Indoor plaster needs nothing added. The outdoor plaster can be waterproofed with emulsified asphalt which is used for cold process highway repairs. (12 to 16 ounces per wheelbarrow.) You might also be able to find some latex/acrylic at a paint manufacturing facility. Elmer's yellow, waterproof glue will work if you can find it. About a pint per wheelbarrow. Fish oil emulsion is used in Chile. If you use too much of any waterproofing material, the plaster will be unable to breath out any water vapor that gets into the wall and then the plaster looses its bond with the bricks. If you have a good old Panamanian roof of thatch with a lot of overhang, your problem is already solved. You might also look around to see what the local populations have developed where there is still earthen construction. Panama experiences more rain than most other locations. Q: Can you seal adobe brick. If so with what? I live in a adobe house the brick wash away every time it rains or it gets windy out. A: There is a product called OKON. It is formulated in w-1 and w-2. I can never remember which is the right one but the company or a distributor should be able to advise. OKON is invisible and breathes so water vapor is not trapped inside the adobe bricks. They were located in Colorado and could be found at www.okon.com . The company has been bought up by a chemical giant but the product should be available. There is no magic bullet other than mud plaster that is renewed every year or so or a cement/lime/sand standard stucco or a lime/sand plaster. Q: We live in North Carolina - plenty of red clay soil. Can I use this soil mixed 3:1 with Portland cement and plastered on (ca. 5 in thick) chicken wire to cover an adobe bread making oven. A:
I don't think that Portland cement is the right thing to add. Portland and clay are not compatible and work at ruining each other. Lime might work, emulsified asphalt might work. If you can find the highest clay content that will not crack that will give the best natural water resistance. As sand increases in a plaster mix, there will be less or no cracking but the water resistance begins to decrease. It's a balancing act. |
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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, 
