Our adobe house was our first DIY building. We chose adobe for a variety of reasons: natural building, low cost, amenability to DIY building, and being a part of indigenous building tradition.
The issues worth sharing about our experience include the reasons for our choice of materials, building techniques, positive features of building with adobe, downsides of an adobe home, and personal insights into our relationship as a couple as a result of a cooperative DIY building.
As complete novices to DIY adobe building, we began by reading about the process. Two of the most helpful books can be found in our book section with a link to Amazon. One is Adobe: Build It Yourself by Paul Graham McHenry and the other is The Natural House by Daniel Chiras. (see the book list page)
In choosing adobe as the material for our first house, we considered the historic role of adobe in the Southwest - including indigenous building sites as well as factors such as low cost of building material, no expensive tools, and the amenability of the material to DIY building by novices.
While adobe buildings existed in Africa and Asia for thousands of years, the Southwest United States sites built by the Anasazi such as those in Chaco Canyon and Mesa Verde date from about 800 to 1100 C.E.
From these beginnings, later Native American tribes continued to utilize this local material for buildings being used today. Communities such as Tucson, AZ have commercial adobe production furnishing adobe block to builders around southern Arizona.
The fact that adobe blocks are essentially a mixture of clay, sand, and some binding material that ranges from straw to horse manure means that material for making blocks can be found in many areas of the state.
We live on an alluvial plain or bajada and have too much silt in our soil for good blocks. There is a great clay mine within a short driving distance so our adobe clay was inexpensive to have brought on site. Our initial loads were less than $25 per ton.
While later in our building process, we used a small electric cement mixer, our Bear Cave was mixed with hoes in heavy black tubs. Our tool set included hoes, trowels, shovels, a wheel barrow, 1/4" screening, and forms made from 2x4 dimension lumber. We used the same material for plastering as for block only processed through a finer screening.
Perhaps the factor of working with adobe that makes it so amenable to novices building an adobe house is the fact that it is forgiving. With concrete or any cementitious plaster, once it sets up there is no change possible. You just start over. With adobe, a bad or broken block is just tossed back in the tub, soaked with water, and reused. You do get "overs" with adobe.
The following links are to pages providing a pictorial process for the stages of building the Bear Cave.
Adobe Block - Adobe block and adobe plaster are the keystones to all of our buildings. Easy to use from local materials, we used adobe for a wide variety of purposes from wall plaster to walls to a foundation.
Stem Wall - The footings and stem wall of our adobe house were designed to support a heavy wall. The footing was about 16" wide and 4" inches thick with two rows of rebar running parallel around the building. The monopour concrete stem wall was poured in a form above the footing. The description for this stem wall is on the footings and stem wall page of the straw bale house. Please just follow the link.
Utility Rough In: Raceways for water and electricity were in place before the stem wall was poured.
Sub Floor: A subfloor of rough fill with four inches of AB road mix was leveled and tamped prior to beginning the wall.
Laying Block Walls: The block walls were laid using a running bond. The first course was secured to the stem wall with rebar pinning. Corners were "tied" with rebar every third course.
Door and Window Bucks: Door and window bucks were leveled, plumbed and braced as block was laid around them.
Electric Fixtures, Outlets, and Switches: Conduit and electric boxes for outlets and switches were installed as the wall was laid.
Bond Beam and Trusses: We used 2 runs of 2" x 10"s to create our bond beam and anchored it with pins piercing the top run of block. The dimension lumber was installed with a running bond. For this building, we built our own trusses. I will discuss these, but advise you to buy fabricated trusses. Inexpensive and stronger.
Purlins vs. Sheathing under Steel Roof: For the Bear Cave, we chose to attach the roof steel to purlins attached to the trusses. Again, the learning curve. The roof is fine, but I would use sheathing as we did on the house if doing it again.
Front Porch: We created a pitched roof including the front porch by attaching rafters to a plate on the front of the truss. Strong and works fine. The porch posts, anchors, and flagstone are similar to the techniques used on the house.
Although we much prefer our straw bale buildings for ease of building, energy efficiency and practicality of hanging shelves and fixtures, I am happy to have had the experience with adobe. We love our cottage as do the many guests from all over the world that have stayed in the Bear Cave BNB.
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