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roof: putting on a 2nd layer of plywood -- good? bad??

Postby applesusan » Thu Sep 24, 2009 4:54 am

In the process of tracking down/repairing some leaks in a relatively newly shingled roof (5yrs), we discovered that several spots on this part of the roof were quite soft. We thought it might be rot and began ripping out shingles/felt. Only a little bit of the wood has been exposed so far but that isn't rotten. It is just that where two pieces of plywood come together and aren't near a rafter, the wood bends ... a lot. One guy suggested we could lay down a second layer of (thinner) plywood on top of the first in a different pattern to give the roof strength instead of ripping out and replacing all the old plywood (assumng none is rotten). Does any one know if this is a good idea, a bad idea, or....
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Postby stoneyboy » Sun Sep 27, 2009 9:53 pm

If you can get to underneath of the existing ply you could add noggin strips to support the joins.
If not adding an extra layer of ply is a good idea but will entail a complete roof strip.
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