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Old 04-02-2012, 06:44 PM   #1
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Roof Sheathing

I have a question about a project I started and has turned into a logistical disaster.

Was planning on replacing my shingles. Two days to tear them off and put titanium paper down then 2 days to put the shingles on. Ran into big trouble. Seems all the boards are bad. All of them. 24 square. They are 3/8 inch plywood that appear to be fried. The glue is totally fried and they just peel apart and are very gummy. A ridge vent was later cut into the boards, I assume when the shingles were put on in 1998.

My question is this. Could those boards have gone bad with a roof vent and lots of vented soffit in 14 years? The person I bought the home from a year ago stated they replaced the roof in the sellers disclosures in 1998. Are they lying? I think so. It seems to me these are the original boards that they later cut the vent into, you can see the circular saw marks in the joists at the peak, and not new boards.

Could those boards have gone that bad in 14 years under new shingles with tar paper and ice & weather guard on them and a ride vent and soffit? You can peel the boards right apart and they are as spongy as a trampoline if you don't go right through them.


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Old 04-02-2012, 08:46 PM   #2
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Very possible.

Bad batch of glue at the plywood factory will do it.

3/8ths is not ideal for a roof deck in my opinion too.


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Old 04-02-2012, 09:57 PM   #3
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3/8ths would make for a very spongey deck even after the new shingles are installed. We dont even offer 3/8ths, in my neck of the woods 1/2" is minimum.

It is never fun to tear off and see massive amounts of wood damage, no one likes to hear they need hundereds to thousands of dollars additional work
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Old 04-02-2012, 10:03 PM   #4
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The only time I've ever even seen 3/8 used on a roof is in a cheap mobile home.
Should have been a minimum of 1/2" with H clips between the rafters to keep it from sagging.
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Old 04-05-2012, 02:52 PM   #5
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Joe, back in the early 60's when plywood was first being used, 3/8's was common. Now we want more.
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Old 04-06-2012, 07:10 AM   #6
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Is it interior grade plywood? Seen this on a few roof decks, not good!

Everybody seems to things plywood is better than osb but I see a lot more issues with plywood roofs than osb roofs. You would think if plywood was really better they would make siding out of it! Example/ LP Smartside osb based...
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Old 04-06-2012, 08:15 AM   #7
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Just because they replaced the roof doesn't mean they replaced the sheathing. And 3/8 ply or 7/16 OSB is minimum code, and contractors will take the pocket dollars over more expensive and stronger lumber.

But I did re-roof some townhomes that had to have 30% of the 3/8 plywood sheathing replaced, and they were only 17 yrs old from new.
But they had no venting what so ever.
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Old 04-07-2012, 12:05 AM   #8
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Half inch min on the sheeting! Plus sheeting could have been bad when they put in the vents and just felt what the hell we going to sell this home so who care's. I would replace the sheething with 1/2 in CDX plywood min of five plys.
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Old 04-07-2012, 06:59 PM   #9
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Just did a roof job today, right off the bat I knew it was old 3/8" cdx cuz of the spungyness but about 8 sheets had to be replaced with the same 3/8" because they were delaminated. I can say that most of the house on that coldisack were probable 3/8" used back in that day, I didn't think either that anything less then 1/2" would be used but we are talking late 60s easly 70s.


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