Flat roof repair

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Mar 8, 2020
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We had a massive, much needed rainstorm a couple weeks ago but the downspout for the flat-roofed section of my mother-in-laws house clogged, the roof flooded and water leaked into the exterior wall of one bedroom. I suspect the water got deep enough that it simply over-topped the edge of the roof barrier. However, it is clear there is enough damage that serious maintenance is needed. The first photo below was taken from beside opening to the only downspout. After clearing the clog there was still some standing water right beside the downspout. It looks like the roof was previously treated with some kind of elastomeric coating. That coating is badly degraded in several areas but because the interior ceilings show no evidence of water I suspect (hope) those deteriorated spots (like in 2nd & 3rd photos) were not the source of the leak. Also, joints between sections of the perimeter wall cap are starting the separate (4th photo) and nails under mastic on top of the cap are starting to be exposed (5th photo).

At minimum, some maintenance is needed on deteriorated spots. It appears impossible to hire a roofer right now. Three I called said they are only doing replacements, no repairs. Whether for spot repairs or recoating the entire surface, do you recommend silicone or acrylic based elastomeric coating? Something else? For joints between wall cap segments, and to re-cover nails, is something like Henry's Wet Patch OK or should I use something else? Thanks.


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