Making Adobe Bricks

Making adobe bricks is demanding in many ways, but when you've finished building a wall or a house, all the more satisfying in the end.

| March/April 1981

068 making adobe bricks - compression test2

With this apparatus you can conduct a simple compression test.


The following excerpt from The Owner Built Adobe House by Duane Newcomb is from chapter three, "Making Adobe Bricks," and is reprinted with the permission of the author.  

Modern adobe bricks consist of a mixture of clay, sand, straw, and emulsified asphalt.

Clay holds your bricks together just like the cement in a concrete block. It contains primarily an aluminum salt and is made up of extremely fine particles. There are several different kinds of clay, but you can use any one of them for making bricks. The so-called adobe soil of the Southwest actually contains too much clay to produce good bricks. What you need is a sandy clay or a clay loam. Soil with too much clay produces too many shrinkage cracks. Soil that is too sandy crumbles easily. If, after a soil test you find that your ground has too much or too little clay, you can bring in sand or soil with a higher clay content as needed.

Sand, the second ingredient used in making adobe bricks, actually is an inert filler held together by clay, much like gravel in concrete. You can use almost any type of sand in making bricks except beach sand, which contains too much salt. Add extra sand to your soil only when you need to lower the clay content to meet code requirements.

Straw, the third ingredient, doesn't add strength but binds a brick together and allows it to shrink without cracking.

Emulsified asphalt (a petroleum residue utilized in paving) makes the bricks water-resistant. In ancient days the Babylonians succeeded in making waterproof brick. The art was lost for centuries, then rediscovered about fifty years ago. Without the addition of emulsified asphalt, unprotected bricks soon weather away. With it, the bricks stand for many years without appreciable damage.

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Sept. 15-17, 2017
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