The Passion of the Un-Chaste
Twice a week, on average, someone accuses me of being a purist (I can at least be grateful that they aren't using the words "pure" or "Puritan." In neither of those forms does the word fit me well). I do take some passionate stands regarding adobe construction, partly because I love the material, but also because no one eagerly anticipates reading the apologies of a phlegmatic moderate on Sunday morning.
My "purist" approach to adobe construction and conservation is based on one principle -- the remarkable success and longevity of earth as the basis for building when it is constructed into a system of compatible materials in a logical spot. Applying this principle, I utterly reject using the word "adobe" to describe a house built on a hillside, of soil blocks saturated with up to 12% asphalt emulsion, laid up in a rigid Portland cement mortar, capped with a concrete bond beam, sprayed with polyurethane and then coated with a polymer-based render. That is a composite at best; at worst it is an abomination in the biblical sense.
This is not to say that I reject or even avoid modern components when building or repairing. Quite the contrary, I endorse concrete and steel as the most brilliant engineering materials ever invented and use both when it makes sense. Footings, for example. I am also a mega-fan of helical piers, galvanized steel screwed into the ground and used to support buildings, including historic ones, that would not otherwise stand. Among the other modern materials that I use and endorse all day, every day are bituthane (the thick rubbery waterproof membrane with the kraft paper that you remove from the sticky side), and geodrains, polypropylene sheets sandwiched between non-woven geotextiles, or filter fabrics. We also use miles of 3" polyester strapping in both new construction and restoration.
All of these materials are modern and, one would assume, utterly incompatible with a soft material like adobe. Nuh-huh. It is all in the way they are applied.
In the world of architectural conservation there are two basic tenets that we follow when designing and implementing structural interventions in older buildings; compatibility and reversibility. We almost never use concrete in a retrofit because it is neither compatible nor reversible, at least not without a totally invasive approach such as, say, jackhammers.
Steel is different. When we have an old adobe building without a footing, we will typically install helical piers and to provide span strength from point-load to point-load, we will use structural steel. The beauty, the elegance really, of the system is that it is completely reversible without leaving a trace and without inflicting damage.
And, where nearly every contractor I know finds it satisfying in a macho sort of way to drive a piece of re-bar into the top of an adobe wall to "anchor" his bond beam (and shatter his wall), we use poly strap. In new or old buildings, we run the belting through the wall four or five courses below the beam, then pull it up over the wood and screw or nail it down. Effective, non-invasive, reversible, strong. And, I have most local engineers and code enforcers sold on it.
So there! I am not the anachronism that some people believe me to be. And I am certainly not pure.