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....
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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