Saturday, July 19, 2014

The Adobe--Part 1 Gordon Rottman



The Adobe—Part 1

The adobe building was the most common shelter in the old southwest. They were a great deal more common that the wood-frame and plank ranch houses with wooden shingle roofs depicted in Western movies sitting in the middle of desert. was too far from sources of scare trees and sawmills. Besides the excessive raw materials costs, freight transport was high.
Adobes were common in south and west Texas, northern Mexico, and the southern portions of New Mexico, Arizona, California, and elsewhere. These places are characterized by hot dry climates and so happened to possess an abundance of the raw materials necessary to make adobe mud—dirt.
The word goes back to at least 2000 BC, the ancient Egyptian dbt for mud brick with the modern spelling coming from Old Spanish.
Part 2, Raising an Adobe House, will appear here on July 21, Monday.

http://upload.wikimedia.org/wikipedia/commons/0/0f/Callejon_de_Huaylas_Adobe_House.jpg
Simple adobes under construction. Note the modern tile roofs.

Morelos, Coahuila
I took an interest in adobe construction after examining buildings and compound walls in Morelos, Coahuila in northern Mexico, my wife’s hometown. The town and the other four towns of Los Cinco Manantiales—the Five Springs—are about 30 miles across the border from Eagle Pass, Texas. The communities were established some 170 years ago and some original adobes still in use. We have relatives living in adobe homes build around or even before the turn of the century (the one before this last one). They’re structurally sound and built like forts. They’ve been modernized of course with electrical outlets, lighting, water and sewer lines. Many are now air conditioned. Most have the original exterior plaster, although this occasionally requires patching. In most cases the original interior plaster was removed and a more durable concrete-based plaster applied. The floors in most are a layer of adobe bricks overlaid with attractive title. In a few instances the base bricks broke up and were replaced by poured concrete with iron rebar, sometimes after laying water and sewer lines. In the old days a smooth layer of thick plaster was laid on the floor bricks. Floor tile came with increased prosperity along with indoor plumbing in the 1960s.
The exterior walls are 18 inches, sometimes 24 inches thick making for interesting and utilitarian window sills. Interior walls are 10-14 inches thick. All walls are considered loadbearing. Interior and exterior plaster could be 3/4 to almost 2 inches thick and using the same mud as for the bricks and mortar.
Asking about maintenance is like talking about the passing of great grandparents. The last repairs were always a long time ago. Unlike modern North American homes with weathering, paint peeling, dry rot, termites, deteriorating roofs, etc, it’s just not a concern. I’ve asked about roof leaks and everyone looked at each other like it’s a subject that’s never thought about. Finally someone will say, “We have never had a leak.”

Making adobe bricks
An adobe house can be built almost entirely from locally available materials, de la tierra—from the earth. The soil is tested by filling a large glass jar with 1/3 earth and 2/3 water. Its shaken vigorously and then allowed to sit until the water’s completely clear—one or two days. It will settle in three layers—top to bottom: clay, silt and sand, and course sand and gravel. A good mix for adobe mud is 15% clay, 10-30% silt, and 55-75% sand/gravel. Mixes will vary greatly. Up to 25% or more clay is preferred by many and there should not be too much gravel. Old builders dug the soil from favored quarries, even if it meant transporting it some distance. It was mostly dug from river banks with an abundance of clay, sand, and silt.
Adobe mud is not created by adding specific percentages of clay, sand, silt, and gravel like concrete. It comes “pre-mixed” in the soil that is selected. The mud is mixed on the construction site in a 5-inch pile spread on the ground, lower in the center. Small amounts of water are poured and uniformly mixed with a hoe eliminating lumps to create a stiff mud.
A 3-inch layer of 4-6-inch long chopped straw is spread over the mud—one part straw per five parts soil. Dead weeds, finely chopped twigs, and cow manure can be used. The fibrous material is completely worked into the mud. Once dried, abode bricks made with manure do not smell and it repels insects. The straw does not strengthen the bricks. It allows the bricks to dry evenly and quicker to reduce cracking. After the turn of the century, cement or lime was sometimes added to make them more durable and waterproof. Today liquid emulsified asphalt is used for the same reasons.
The mud is shoveled into wooden forms. Forms are not always single bricks, but multiple bricks, five or eight, for example. Bricks can be 3-5 inches thick, 8-12 inches wide, and 14-18 inches long. There is no standard size. It’s the builder’s preference. They are generally the same size for a specific house. Exterior walls may be 14-36 inches thick, usually toward the thinner. Smaller bricks might be used for interior walls though.

http://i961.photobucket.com/albums/ae91/Vons_photos/IMG_1025.jpg
4 x 12 x 14-inch adobe bricks. The crude mortaring will be plastered over.

Bricks are removed from the forms after a day or two and laid on level ground to dry further. They are not stacked as the bottom ones could break. Broken bricks are okay as many half bricks are needed. Bricks are laid in the shade to dry. If sufficient shade trees are not available, leafy branches are laid over them. Drying too fast in sunlight will crack them. After a couple of days they are set on edge with an airspace between them to dry for up to six weeks. Two men can make 200-300 bricks a day. Like Rome, adobes are not built in a day. Nor can it be done in the rainy season. Once completely dry—2-3% moisture content—bricks can be stored for extended periods and stacked, but it is best to store them on edge with air spaces. They can still absorb moisture from humidly, dew, and showers.

13 comments:

  1. Fascinating. Thanks, Gordo.

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  2. Great article! I am surrounded by adobe and the last buildings of Badito, CO are now (unfortunately) returning to the earth. So many historical adobe's in Colorado are allowed to fall apart. I don't understand this.

    Thanks for this piece.

    Charlie

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    1. That is sad that at least a couple were not preserved. I had suggested to the major in Morelos that the oldest adobe be identified and preserved, but they don' have too much of a sense of preserving history in small rural ranch towns. There's too much everyday work to do.

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  3. In one of my first westerns, the proofreader, who'd probably never been west of Manhattan, changed every instance of "adobe" to "abode."

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    1. Sigh. If only you would learn to spell, Bill, you might make it as a writer.

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    2. That some how comes as no surprise.

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  4. Interesting post and I look forward to the sequel. I've always been fascinated by adobe construction. My dad was a masonry contractor. Thought about test-building something small...maybe a dog house!

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  5. I love the look of the adobe construction. This was an eye-opening post. Thank you. Doris

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    1. Me too. We considered building an adobe in Morelos, but will probably go with the more durable current concrete and cinder block construction. But, I'm going to at least have some adobe interior wars as well as the compound wall in adobe.

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  6. Gordo, this is fascinating to me. I never knew any of this--only that I have always loved the way adobe looked. I know you have Part 2 of this article coming up on Monday, and I look forward to it!
    Cheryl

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  7. Gordo, this is great! Would that every young homeowner have the chance to lay his/her own bricks. My grandpa could lay the straightest row of cinder blocks ya ever saw, all day long with nary a waver. Alas, a talent I didn't inherit.

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    1. Folks built their own sometimes, but usually had some degree of previous experience. Mostly they hired experienced builders. I know they took great pride in squaring buildings.

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  8. Thanks for a most interesting article - looking forward to Part 2!

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