I need to reshingle my roof and some of the 3/8″ roof sheathing has gone bad. Can I lay 1/2″ sheathing over the entire existing 3/8″ or do I need to remove the bad sheets and replace them individually? Thanks for any help you can provide!!
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I doubt that "bad" 3/8" sheathing will hold fasteners very well, and you may also have a mold issue if the sheathing got wet. 3/8" is not very strong for sheathing to begin with, and I doubt it is to code, I think you should consider a complete replacement if you can afford it.
Either way, be careful up there as you most likely do not have very solid footing up on your roof.
Don't even think about walking on that stuff, you'll go through in a heartbeat.
Hurts. Could hurt worse.
Joe H
If it's damaged, I'm betting that it either got wet, is delaminating, or both. I'd have to say you should replace it out right. I'd use 5/8" fir this time.
3/8" ply on 16" centers is rated 40 psi total load. Just make sure the nailing schedule is spot on or better.
Adding 1/2" adds weight... make sure you have the rafters to hold it.
Certainteed Hatteras (8" exposure, 18" tall, 110 mph wind rated) shingles call out 3/8" on 16" centers as the minimum sheathing to hold them DOWN.
If 3/8" will hold those big shingles on the roof... ya gotta think what the 1/2" is worth to you, 'cause it ain't gonna keep the shingles on any better.
And really, how often are ya walkin' 'round up there, huh?
Troy Sprout
Square, Level & Plumb Renovations