A view of the new exterior earthen plaster crisp in contrast to the older small window in this
300 ft. casita. This building and walls has been exposed to the elements for many years and was in need of infill mud repair to the worn adobe walls.
During original construction the roof eaves were not long enough to protect the adobe bricks, let alone a non-water proofed earthen plaster. As is common knowledge in the natural building world, one cannot apply an earthen plaster on the outside of any structure and expect it to last year after year. The idea is a bit like pointing a water hose in the mud, it disintegrates as mud will do. An option which would have worked for many years is either a lime plaster (water resistant) or the more common solution in northern New Mexico, that or applying a cement stucco.
However the owner knew what he wanted, so we set about to create the strongest earthen mix we could think of. We not only supplemented it with a strengthener, but also painted a coat of the same clear substance on the outside of the walls. We have had some luck with this process on interior walls and decided we would use this structure as a bit of a test building. So far, the walls are doing well. We do however, expect the earthen plaster to wear over time, for the reasons stated above.