Reroofing with Ply? Anyone in the Know?
When is it necessary to use plywood (OSB) during a reroof? I have seen roofs stripped on older single story homes (1950,60’s) and sometimes new ply is put down before the felt and shingles. Other times no ply, just felt and shingles over the slatted gable roofs. Is there some building code warranting this, is it overkill or what?
Replies
A lot of times the boards were beaten to hell from the inside due to moisture trapment. Plus a gent told me that plys were not used back then due to the glues were not of the standard of today. Fell apart so he says. But my bet is on it was rotten T n G.
The Harv
Standards call for spaces greaaater than 1/2" betwen boards or where there are loose knots to be patched with metal to support the new asphalt shingles. Also, a roof that has been re-roofed a number of times will have so many nails driven into it that the boards are full of splits and can look like broom straw. They won't hold a new nail. not even the 8d that's holding it down to the rafter. So it's not always rot. You need support under the shingle and enough integrity to grip the new fastners. If the old material won't satisfy those requirements, you replace or recover it.
Most around here are sound enough with a minor repair here and there but I've found that it's safer to just plan on adding a ply of 3/8" cdx or 7/16" OSB right over the existing and including it in the bid to avoid surprises for anybody.
Someitmes the labor pays for itself because the shingles can be so much easier and faster to apply when you are not fighting with bouncing deck boards, searching for sound nailing, etc. A smooth, sound deck will extend the life of the shingles too. and if you try to take off a large section of roof as I like to do, you can be more confident that the felt will stay on overnite because it will be harder for wind to get under it and uplift.
The best explanations that I've heard yet! So one really does'nt know if they will need to use ply until the strip has been done. So it's best just to plan to do it even if your final analysis is that you don't need it. Thanks guys!
actually.. if you can get up in the attic.. you can usually get a good idea if it's going to warrant a ply-over.. lots of broken boards... rotted areas & big gaps make it a no-brainerMike Smith Rhode Island : Design / Build / Repair / Restore
Or, If i'd been in the same place all my life, I'd have already roofed it once or twice myself.
So I'd know.
Excellence is its own reward!
The attic is easily accessible, and everything looks solid,dry, and tight from underneath. Not even any (obvious) termite damage. Looks like I might have to replace a board or two along the eave (about 8-10ft). I'm having shingles torn off on friday (2 layers), so I'll know more by then. By the way, this is taking place in Los Angeles. Thanks again, Ken