Matt Melton lives in central Washington state in a 3-year-old house with a roof made of structural insulated panels (SIPs) that are 12 1/4 inches thick. The pitch of the roof is very low, only 1/2 inch-in-12, and the metal roofing has been applied directly over the SIPs with no air channel beneath the roofing for ventilation.
When the house was built, Melton sealed the seams between roof panels with tape, applied on the bottom of the panels. The top of the roof was completely covered in a peel-and-stick membrane. In both cases, Melton now says, the seams of the tape and the roofing membrane didn’t seem to stick very well.
This year, there’s trouble. For the first time, Melton has noticed an ice dam on the roof. Worse, he reports water leaking through a seam between SIPs, although the leak appeared on a roof overhang and not in the interior of the house.
“Now, I’m wondering should I pull all the roofing off once it warms up and let the thing dry out and also to see if there is any mold,” he writes in a Q&A post at Green Building Advisor. “Then maybe replace with a better underlayment and a TPO roof?”
There’s one more complication: Melton has sold the house and is now renting it back from its new owners. They apparently plan to take possession in May.
How should Melton deal with this developing problem? That’s the question for this Q&A Spotlight.
A site visit is a good first step
GBA senior editor Martin Holladay makes five observations: installers used an interior tape with adhesion problems; there is evidence of air leakage at the seams between SIPs; it appears that melting snow on the roof caused by air leaks led…
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