Question:
Looking back over your experience, on average, what is your estimate of the percent of the “forensic problems” in homes that you have examined were due to genuine defects in materials (such as fire-rated plywood (FRT) in the early 90s), versus what percent were due to workmanship, improper application (as in right product for right job) or improper (or otherwise ignorant) installation?
As an example, regarding the exterior finish insulation system stucco problem, was it purely a materials issue, meaning that there was NO WAY it could have been installed correctly by anyone? Or was it a viable system, if installed correctly? I have heard both claims.
-Scott Sedam, TrueNorth Development, Inc.
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Answer:
Like anything in building science, the answer is “It depends.” I think there are really four main answers to the question. Bad materials used poorly tend to fail quickly so builders won’t use them anymore. Good materials executed well will last and perform for a long time in most climates. This leaves two categories, slightly different from those posed in the original question.
The performance of materials can only be determined when they’re observed in context of their installed environment. For example, we have observed many window installations that only leaked on end walls of homes. While the window installation was flawed, overhangs on the front and back of the home reduced the exposure to a point that didn’t show evidence of that failure. We have also seen windows installed in walls where only the large windows failed. In this case, the bending induced by high winds was severe enough on large windows to crack the corner welds. Orientation and exposure are critical factors in generating system failures.
Making changes to many systems and products in a house can also lead to a failure, which may not be the pure fault of the product. A good example is the presence of mold behind baseboards. The homes have been built the same way for well over ten years, but recently mold has shown up behind baseboards. What changed? The baseboards changed from wood to medium density fiberboard (MDF). But the homes also had added insulation and better performing windows, resulting in lower cooling loads. The lower cooling loads resulted in less air conditioner run time, and therefore often less dehumidification. So, a baseboard that was slightly more capable of drying in a higher drying potential environment worked, while a baseboard with slightly less drying potential in an environment with less drying capability failed. Because the mold shows up behind the baseboard, it appears the MDF is at fault; however, the fact that the air-conditioning system does not keep the house as dry also has an impact. There’s nothing wrong with the material itself, it’s just being applied in conditions that don’t allow it to perform in the way one would expect.
To address your question about the exterior finish insulation system problem in the southeast: yes, the system really could never be installed to work because you have to assume that the seals will fail, and you need to plan for bulk water management. Custom details and double vapor retarders really spelled doom from the start.
Certainly, even good materials can fail with poor workmanship. I guess the winner is most problems occur from good materials and systems being used poorly—poorly both in the sense of improper field execution, and in terms of being specified for inappropriate exposures and conditions.
-Brad Oberg,
Chief Technology Officer, IBACOS
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