Am I correct in understanding that the valley flashing was looted, but the balance of the asphalt roof in is still in place, so there are just valleys in play here? 30 lengths where the dormer roof meets the rake of the larger roof plane?
First off, I would confirm that the deterioration is extreme enough and widespread enough that an experienced roofer can't manage, albeit carefully. Some lengths of roll roofing and adhesive/sealant might be the most roof-ey temporary solution. Not elegant but, literally, a bandaid.
Spray-on membrane in roofing is one of my least favorite systems, but it is made for being impervious and exposed to the elements. I would think that that would be a better strategy than just plain closed cell spray foam.
Allowing the saturated stuff, below, to dry out is another consideration....but that is the case regardless of strategy.
An interesting problem! Good luck!
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Peter Franks AIA
The Franks Design Group, P.C.
Glenwood IA
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Original Message:
Sent: 05-31-2019 13:56
From: Katherine Dowdell
Subject: Temporary roof repair question
I'm working with a small "friends of" group, to try to keep a former mansion in the center of what is now a public park from being demolished by the county who owns it. County ownership has not been kind to the building, and although the main hip roof (asphalt shingles, fairly steep slope) is still in decent condition, there are 15 or so large dormers, which have been stripped of their copper valley flashing, so water has an easy entrance into the building (and has for years). The roof sheathing and framing is now deteriorating, and the county is wary about anyone walking on the roof, even to do repairs. Someone has proposed closing these valleys temporarily with spray foam insulation, which could be done from a high-reach and is waterproof enough to last a few years at least. To be clear, we'd be using the spray foam as waterproofing, not for any insulation value - the building is vacant. This is just to try to get it buttoned up so we can start to dry it out.
I can't think of why this wouldn't work - any thoughts or feedback welcome.
Kathy Dowdell