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don62
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# Posted: 18 Sep 2017 22:11
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I'm gonna resheet my roof, I'll be using 1/2 inch 4 ply . My question is, should I use 2 1/2 inch ring shank nails from an air nailer or 2 inch coated deck screws. I have plenty of both so I don't have to buy anything, is one better than the other for any reason??
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ICC
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# Posted: 18 Sep 2017 23:01
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No to deck screws; not approved by code. They are case hardened and brittle. Nails are malleable and bend before breaking. No sudden failure.
Nails for 1/2 or 5/8" roof sheathing are spec'd to be
8D common (2-1/2" x 0.131" shank). Air nails are usually smaller diameter, maybe as small as 0.113", more like a box nail is sized. So you need more of them. In an 8D size you need about 25% more box nails to equal the strength of common nails.
So something like 4-1/2 inches apart around the edges of the panel instead of 6" for common. In the field of the sheet then about 9" apart instead of 12 inches.
Reference on substituting
code nailing table (scroll down)
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snobdds
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# Posted: 19 Sep 2017 00:31 - Edited by: snobdds
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This is an area where I have evolved to really like staples and OSB sheeting. Coated 16 gauge crown staples are what I use on all sheeting projects now. It takes a few more staples, per sheet, but it's cheaper and easier to fasten down and provides the same sheer strength. Now if your set on using plywood, then I would use the ring shank nails in the nailer.
Definitely don't use screws.
Here is some light reading on the topic...Specifically look at page 25.
http://www.icc-es.org/reports/pdf_files//ESR-1539.pdf
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don62
Member
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# Posted: 19 Sep 2017 14:26
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Thanks for the replys, I already have the plywood so I'll use it and nails are the plan.. thanks a lot...
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KinAlberta
Member
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# Posted: 24 Sep 2017 21:53
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So - maybe a dumb question here, but if the original sheathing is left in place (if allowed) aren't shear requirements already met?
So wouldn't screwing on (or both nailing and screwing on the new layer) provide significant improvements to the overall roof strength. Additionally, if a new second layer of sheathing was overlapped and glued then wouldn't you have bragging rights to some amazingly strong roof? 
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ICC
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# Posted: 24 Sep 2017 22:50
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Quoting: KinAlberta but if the original sheathing is left in place (if allowed) aren't shear requirements already met?
Perhaps the original sheathing had been weakened by water damage? Why else replace sheathing?
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KinAlberta
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# Posted: 25 Sep 2017 10:12
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Quoting: ICC Quoting: KinAlberta but if the original sheathing is left in place (if allowed) aren't shear requirements already met? Perhaps the original sheathing had been weakened by water damage? Why else replace sheathing?
Yes, on the poster here said it had to be replaced.
A couple years ago I posted somewhere saying that I’d put 50 yr shingles on my house. They responded with a post about how it’s a scam because typically the sheathing isn’t being renewed and old sheathing deteriorates, delaminates or some such thing. News to me and I’m still not sure if it’s believable or generalizable information.
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ICC
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# Posted: 25 Sep 2017 10:29 - Edited by: ICC
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Quoting: KinAlberta A couple years ago I posted somewhere saying that I’d put 50 yr shingles on my house. They responded with a post about how it’s a scam because typically the sheathing isn’t being renewed and old sheathing deteriorates, delaminates or some such thing. News to me and I’m still not sure if it’s believable or generalizable information.
The only sheathing, wall or roof, that I have ever seen need replacing was because of water or termite damage. A couple years ago we re shingled a house that was built in 1972. We stripped all the shingles and roofing felt. The only sheathing we replaced was where the chimney penetrated and that was because we removed the chimney because he installed a new 97% efficient furnace that no longer used that original chimney.
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