Here in Montgomery, Al, we are encountering some roofs that were built back in the 70’s and they were decked with 38 plywood. This stuff is so brittle that you cannot walk on the roof unless you step on the rafters.
We are going to redeck some on these. Do you guys think it will be alright to take off the shingles and deck over the 38? Will number 8’s be long enough or should we use 12’s? WE are going to put 716 osb on top. The rafters are 24 inches on center.
It is my intention to deck over the old. We have never done this so I’m wondering if I am on track with my thinking.
James
Replies
Had the same problem with my house and I went ahead and decked with 5ply 1/2" cdx over the old 3/8's and it's held fine. As long as there's nothing rotten and the framing can safely hold the plywood load it's ok. I used 8 penny ring shanked nails. The only iffy thing about yours though is that it's 24" oc. Just make sure the rafters can carry the load of the new and the old.
Does this have to do with your felt question?
Tear off the shingles ---redeck with ply ---Paper and shingle.....done.
Around these parts with 24 oc trusses we need 1/2 ply. and we can redeck with ring shank.
I wonder if it is that fire-ply stuff they used then. Guess it got brittle and would spall on the interior if some one walked on the roof . Just wondering outloud.
Hope it all works out for ya. Mike