Embedded Downspouts: A Really Bad Idea
Occasionally in our assessments of adobe buildings we come across the ramifications of a really bad idea. As often as not the evidence will be found either (1) to date from the 1960s or 70s, or (2) in Taos. As you may have guessed, the reason for this phenomenon is counter-cultural in both cases.
Adobe was "discovered" during the heady days of communal living and Taos is home to a relict community of free thinkers. Adobe lends itself to sculptural forms and the incorporation of found materials like twisted wood and interesting bits of glass. As a material it also filled the bill (not really so any longer) for builders on a budget and was correctly recognized as the most renewable material on the planet.
But in the course of re-discovery, local knowledge, centuries old, that provided solutions to certain technical challenges sometimes got left behind. One of these was the abandonment of canales, the protruding drainage systems that take water from the roof and discharge it some distance from the base of the wall.
In place of, or occasionally incorporated with the canal, the nouveau adoberos will sometimes channel out the adobe and embed a vertical PVC pipe that opens to a scupper or drain grate on the roof. The pipe is then taken underground either to daylight or, frequently, to a cistern. The channeled-in pipe is then plastered over.
It's a really bad idea (have I made that clear?). We have found three primary reasons why they fail. First, the grates get clogged with debris and so water puddles on the roof; second, when the house is plastered, the guys nailing the lath into the adobes (a hideous practice in its own right) probably haven't been appraised as to the location of the pipes and so drive 16d and 20d nails right through the PVC. Finally, and this I can really relate to having failed to solder two copper connections in my own sub-floor heating system, someone forgets to glue the joints.
The result of failure is most often a saturated wall indicated by peeling paint and a musty smell. Now that we are attuned to these embedded abominations we can track down the source of moisture very quickly. The first time we met the problem, however it was a different story and we spent a lot of time scratching our heads and probing the walls.
The only effective solution to embedded downspouts is to eliminate them. They don't necessarily need to be removed, but the inlets should be well and redundantly capped and roofed over. Then the plaster should be stripped from the walls to let them dry out. Finally, the parapets should be cut and the roof re-worked to drain into canales that discharge, at the very minimum, sixteen inches away from the base of the wall.