The Adobe House (La Casa Adobe)
February 13, 2007
You can feel the warmth, the spirituality, the charm. It radiates! It has a round and soft feeling. Most appealing is in it's exactness and simplicity. These are the words Danny Martinez uses to describe homes constructed of adobe. Danny and his wife Renee have been designing and building custom adobe homes for 21 years. In 1974 they designed and built their own home. During this process they received requests to build other homes. "Things just went from there,"Danny says.
Included in the Martinez's idea of an adobe home is an active or passive solar design, wooden frame windows, exposed beams, vigas, and brick floors with radiant heat. Richard Martinez, Danny's father adds his touch to the custom homes by carving traditional Mexican designs on the interior structures and doors. All these things together make the adobe home a true folk art which attracts people from all parts of the world.
Adobe is one of man's first building materials. The mass of the adobe walls will absorb heat and radiate it back out into the house at night. In the summer the converse is true. Thus the swing in temperature inside the house is very mild. For thousands of years adobe houses have represented the practical wisdom of people who learned how to use the materials at hand to build homes that fitted the climate and landscape in which they lived. Adobe making runs back to the time of Pharaoh who withheld from the children of Israel the straw for sun-baked bricks. Adobe construction also embodies strands of our southwestern history. When the Spaniards came to New Mexico they found the Indians using adobe, wood, and stone to house themselves. The Indians did not make bricks, but "puddled" the mud allowing each layer to dry before adding more. Adopting these materials the Spanish made moveable sun-baked bricks, formal fireplaces, and wooden doors. "Adobe" is a Spanish word derived from the Arabic "atob," which literally means sun-dried brick. The Spanish brought to the the Southwest the craft of forming the mud into blocks in wooden molds which is still used today.
Today's bricks are 14 inches long, 10 inches wide, and 4 inches high. They are still made with straw to make the dried mud more weather resistant, and also have a small bit of asphalt mixed in to stabilize them. The bricks can be bought at a reasonable price from a manufacturer who uses bulldozers to mix and pour the mud into the forms. After the mud is poured a board is drawn across the top of the forms to take away excess mud and make the surface flat. After the bricks are dried they are taken from the forms and stacked by hand. The average cost of a brick is about 60 cents. Because the weight of an adobe house is so much greater than that of a frame house, the ground must not only be cleared, but should be compressed before the foundation and bricks are laid. If the ground is not compressed there could be movement promoting cracks in the walls at some later time. Next the footing is dug with a back hoe and then hand tampered to compress the dirt once again. In the Albuquerque area the footing is laid about 18 inches below grade (the surface) to avoid the expanding and contracting that takes place when temperatures go below freezing. In the mountains and the colder regions of New Mexico the footing level will be deeper. Both the footing and the stem wall of an adobe home must be larger because of the extra weight of the walls. The footing and stem wall of a frame house are commonly 16" and 6" respectively. The footing and stem wall of an adobe house are commonly 24" and 14" respectively. Of course this increases the cost of adobe construction.
After the foundation is completed, the first layer or "course" of bricks must be laid. This course must be made of special adobe bricks that are made with more asphalt to make them waterproof. It is best is best to lay the adobe bricks in warm weather because the mud used as mortar will freeze. Ditch bank dirt is used for this purpose because it does not have too much clay or too much sand. The right consistency will shake off a shovel. The mud is applied with a shovel and trowel. Each course is laid the whole length of the walls at the same time with bricks overlapping at the corners. Story poles are set at the ends of the walls and support a string used to mark the next course of adobes. Lintels are beams of wood put over the windows and doors. They are often decoratively carved and serve as headers that help support the openings. Construction progresses and adobes are laid one brick at a time with a "more or less" attitude. While, in construction of a frame house, all of the structures and drywall must be measured and cut exactly to fit with precision. People who are sensitive to toxic substances prefer to build with adobe since their is no need to use chipboard filled with formaldehyde.
When the courses of adobes are high enough, bond beams are laid to tie all the walls together and the vigas are laid on top of this with more adobes in between them. The vigas, hewn from trees, make up the ceiling and are often seen sticking out of adobe houses. Traditionally they were not cut off at the walls simply because of the labor involved, but they have since become a notable architectural trait of the adobe house. Over the vigas, latias are laid at 90 degree angles to each other creating a pattern design. Latias are smaller hewn poles made of pine, spruce or aspen. Sometimes today one inch decking boards are used instead of latias because they are more economical. Twelve inches of fiberglass insulation is then installed between 2" x 6" sleepers which are sloped to give a gravel and tar roof drainage. This is called a pocket roof because the space between the ceiling and the roof provides an area for electrical wiring, recessed lighting, and insulation. A canale, or drain channel, is put in every ten feet or so to help any water drain from the roof.
If two inches of foam insulation is applied to the outside walls at this point it will increase the ability of the adobe walls to maintain an even temperature. This will bring a 14" adobe up to an R-value of 22. A screen is applied after that to help the plaster tack to the walls. Plaster is applied in three coats after the foundation, walls, ceiling and roof are completed. Plastering is said to be an acquired skill. Ninety percent of the cost of the plastering is in the labor.
In present day, the adobe house is for the very rich or the very poor, not because of the expense of the materials or the complexity of construction, but because of the expense or availability of labor. Adobe construction is labor and detail intensive. You must be rich enough to hire out the labor, or poor enough to have the time to do the labor yourself. A custom built adobe house will cost about $100 and up per square foot. An active solar design may add $20,000 to the final cost.
A frame house might go up in two months, while a 3000-3500 square foot adobe might take nine to ten months to construct, Typically, adobe walls range in thickness from 10 to 30 inches with 14 inches being the mean. A frame house will have 4 inch walls and about 5% of the house will be consumes in the walls. The walls of an adobe house will absorb 15-20% of the total space because of their thickness.
Builder Martinez uses radiant heat in the adobe homes he constructs. Pipes circulating hot water are contained in floors covered in bricks or saltillo tiles. Radiant heat is more expensive to install but cleaner and more economical to operate. With a forced air heating system you are heating the air and the air leaks out. With a radiant system you are heating bricks that hold heat longer because they have mass.
Some details that add to the uniqueness, charm, and cost of an adobe home are bancos, nichos, trasteros, tile work, corbels and lintels. As mentioned earlier, lintels are carved beams used as headers over openings. Traditionally, when the lintels were very long, corbels were added to help strengthen them. Now, corbels are used solely for decorative purposes. They are pieces of sculpted wood that fit at the ends under the lintels. A banco is an adobe bench, that is usually cut into a wall or built out of a wall. A nicho is a niche. The Spanish carved arched nichos in which to place santos, or wooden carvings of saints. A nicho can be any size or shape and can even be as large as a built in bookcase. A trastero is a built in cupboard. It will have doors on it. Mexican tile work incorporated into the bathroom and kitchen areas add a measure of color and design to those areas. All of these options make an adobe house easy to customize to the owner's particular pragmatic and aesthetic tastes.
Adobe construction has it's roots in simplicity. It was born in climates where there was great space and little water. There is an honesty in the utilitarian attitude of using the surrounding earth, hewn tree trunks from the nearby forest. The inertia of one adobe resting atop another to create one solid mass creates a feeling of non-changing stability that may be translated into a lifestyle.
If you are interested in becoming an owner-builder, Danny Martinez encourages people who want to do it themselves and even teaches a course on the design and construction of the adobe home through UNM's Continuing Education Department. Special thanks to Danny and Renee Martinez for the information in this article and for keeping an important tradition alive.