Rotten sheathing at roof overhang, cause?
We’ve uncovered some rotten roof sheathing on a past project and I’m looking for help understanding the cause. The general details include –
– Climate Zone 4A
– House was built in 2017
– The roof is flat, 1/4″ per 1′-0″ of slope with white TPO as the surface
– The underside of the sheathing was sprayed with open cell foam to R-49
The rotten sheathing is located at a 4′-0″ overhang above the 2nd floor deck. It’s the high side of the roofline. There’s no insulation in the overhang and the soffit is solid. The TPO roof above appears to be intact with no visible entry points for leaks.
I’ve included a photo of the issue along with a snapshot of the plan for reference. We’ve got a few differing opinions on the cause and I’d like to get some opinions from the community here for comparison before we get into repairs to make sure we’re not setting ourselves up for another repair down the road by not properly addressing the root cause. Thanks in advance for any help.
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Replies
I think air was leaking from the house interior into the soffit area there, hitting the cold roof deck and condensing. It doesn't look like there is any venting in the soffits which is probably not helping things.
First thing to check if you have air leaks there, sealing those up should limit the moisture plus also help with energy efficiency.