Full Chisel Blog

April 28, 2008

Adobe

Filed under: Of Interest,Uncategorized — Stephen Shepherd @ 8:51 pm

The first building I ever built, besides a log cabin for a movie was made of dirt.  Adobe or sun dried bricks have been used for thousands of years and when people came out to the West and areas where there is not a lot of wood to build log cabins, adobe was the choice.

Brigham Young had knowledge of this technique and it is ubiquitous in the West.  It is simple, mud, some straw, dried grass, animal hair, egg shells, sand and wood ashes was mixed with water into a thick mud and placed in wooden molds and allowed to air dry and sun bake.

I made a 6 gang mold that would make six bricks matching the size of old adobe bricks and they do vary in size.  These are about 4 inches thick 8 inches wide and 16 inches long.  The mold is made about a half inch larger as there is some shrinkage when the adobe dries.

The adobe mixture is made in a pit and the pits were moved to fresh dirt and the mixing process begins.  One important ingredient that goes largely unmentioned is the addition of wood ash.  Simple ash from stoves and fireplaces add an important ingredient to the adobe and makes it more waterproof than adobe made without.

However given the uniform color or gray of the old adobe indicate that they did use wood ash, and they knew why.  It acts similar to portland cement and the wood ash reacting to water makes for a harder brick.  The mud is then shoveled into the molds, pounded down to remove any air spaces and is screed off to smooth off the tops.

 Adobe Making

The mold is then lifted, it requires two people to lift it off, it is repositioned on some fresh straw and an new batch of mud is is shoveled into the mold and the process is repeated.  Each new day the bricks are turned up on edge and turned over to allow all sides to dry equally to prevent cracking.  The straw, hair, grass all help to bind everything together, but it is important that the pieces dry equally.  Turning is done on a daily basis.

Depending on the weather, temperature and humidity the bricks dry in less than two weeks in the summer, the best time for making bricks.   We were actually building this building as we were making the adobe bricks, I had a helper to do the work but we made the bricks and built this adobe building in about a month, that was in 1977,  the photograph is from today.

Adobe Building

Adobe buildings are cool in the summer and warm in the winter.  Most adobe buildings were covered with stucco or siding to protect them from the weather as they are not fired so they are water soluable.

Stephen

6 Comments »

  1. Stephen,

    Nice building. What is its use? What did you use for mortar? Did the Mormans use adobe in their early buildings?

    Comment by Ron — April 28, 2008 @ 10:15 pm

  2. Ron,

    It was called a dairy building and was built at Brigham Young’s Forest Farm House at This is the Place Heritage Park where I work. (It houses a transformer). It is sand mortar like the originals and the Mormons built a lot of adobes, you can spot them by their thick walls at the fenestrations.

    Stephen

    Comment by Stephen Shepherd — April 29, 2008 @ 6:15 am

  3. Fascinating, as usual.

    Why egg shells?

    What’s the approximate recipe? Or is it measured in “sprinkles” and “handfuls”?

    Comment by Joe Cottonwood — April 29, 2008 @ 12:32 pm

  4. Joe,

    The egg shells are cheap filler and they also resist moisture and will shed rain.

    When you look at old adobies you will find everything, chicken bones, bird feathers and dried weeds, they may have used fresh weeds, they were just dry 150 years later. I even think they put in deer scat as I have seen little cavities that shape with a little fodder attached.I even found a wooden ox yoke bow pin, made of maple and used to lock the bow of an ox yoke to the yoke, interesting find.

    The batches were usually quite large so it was shovel fulls and bucket fulls, I am sure a good batch of a couple of yards would have a couple buckets of wood ashes (2 gallon buckets), a wheelbarrow full of straw, hair, weeds and filler and enough water to make into a thick mud that will not slump when the mold is removed. It may take a day or two for the bricks to get hard enough to turn up on edge. The more water the longer the drying time and more chance of cracking.

    Adobe should be kind of dry when it goes into the molds, so it stands up well and dries quicker.

    Stephen

    Comment by Stephen Shepherd — April 29, 2008 @ 5:14 pm

  5. So The building in the picture is 30+ years old? What sort of maintenance has it required, if any over that time?
    Bob

    Comment by Bob Entwisle — April 30, 2008 @ 12:17 am

  6. Bob,

    There is some damage from water on the lower courses but not much at all, the adobe should be stuccoed. The damage behind me on the corner of the building was caused when horses spooked and tried to pull a wagon between the building and the bush. The bail of hay is to prevent that from happening a third time.

    A couple of original buildings that are 160 years old is not weathering as well. One is scheduled to be stuccoed this year with proper lime stucco.

    Stephen

    Comment by Stephen Shepherd — April 30, 2008 @ 6:23 am

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