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Question DetailsAsked on 11/9/2017

New roof / decking with a damaged plywood decking panel

I had a new roof put in last week. It was a complete tear-down with a new plywood deck installed, covered by new roofing felt layer and GAF shingles. It's a steep pitch roof.

Since it rained yesterday, I went up to the attic to check for any leaks. Looking up from the attic I noticed that one of the new plywood sheathing panels had cracked.

The decking was specified as 1/2 inch, 4ply plywood. This cracked panel looks different from other decking panels. It's roughly 8 inches wide and 3 feet long and has two cracks running along the full length with the panel separating in several places. It looks like it was a fill in piece cut from much thinner part of plywood.

How much of a problem is this going to be for the future? Is it reasonable to have the roofer come back and fix and what should that fix be?

Thank you in advance for your reply.

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1 Answer


Technically a piece that is delaminating or split should not be used as sheathing - but you have to consider the damage to singles (may be tough to get a perfect appearance match if they have to remove some to replace the piece of plywood) and would require splicing of the water barrier, leaving more opportunity for failure of that secondary barrier in the event water gets under the shingles in a storm.

Realistically, if this piece of plywood is the same 1/2" thickness (or more likely in many area, 15/32" / 12mm actual thickness) as the rest of the sheathing, I would not sweat it. Maximum roof loading on that small piece would be not more than 80# - not likely to fail or deflect under that small load assuming it is properly supported

If there are more than a couple of these small patch pieces (unless your existing sheathing is plank rather than plywood sheet) I would be more concerned that this was a scab job - and if the ends (longitudinally along the length of the roof direction) of the piece - or any sheets - are hanging free that would worry me a lot more. The ends of sheets (and at intermediate rafters too) should be supported and nailed on the rafters / truss top chord. Of course, the edges of the sheets (running perpendicular to the rafters) will be exposed without framing under them with conventional rafter/truss framing - modern construction does not put stringers under the joints like old-school quality roofing did. But the ends should be securely fastened, not hanging out between rafters.

If the ends of that patch are hanging free I would say he should come back and support them - I would use pieces of 2x4 or 1x4 attached under the joint using construction adhesive and screws at say about 6" spacing not quite penetrating the sheathing. He needs to be sure not to go too deep and penetrate the roof water barrier or shingles. I would consider this an acceptable fix assuming this is a localized issue - if the entire roof is scabbed scraps that would be another matter and lousy workmanship.

Another alternative would be a 2x4 scrap running between the rafters on edge, toenailed to the rafters or using joist hangers, under the small piece of sheathing and supporting it. Best would probably be one under each side of the scrap centered on the joint, but that might be a bit of overkill. But easy to do - about 15 minutes work plus getting in and out of the attic.

Answered 2 years ago by LCD

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