Minimum requirement for roofing nails sticking through sheathing?
LoudMouth
| Posted in Energy Efficiency and Durability on
Looking at a 2005 tile roof installation manual, it looks like the minimum penetration of a roofing nail into roof sheathing was 3/4″. So If I assume 1/2″ OSB sheathing, I should be able to cut the nails off with 1/4″ still sticking through the sheathing into the attic. Is this correct, or am I missing something?
Dave
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I’m sure your roofing manufacturer would have available downloads of their installation manuals. As I read a CertainTeed shingle installation manual (chapter 8), does not mention a word on cutting off any nails.
"Nail shanks must be long enough to penetrate the roofing and then go ¾” into solid wood, plywood or non-veneer wood decking, or through the thickness of the decking, whichever is less.”
David,
I disagree with your interpretation. Every time I read a requirement that says that 3/4 inch is "the minimum penetration of a roofing nail into roof sheathing," I interpret that to mean that the nail needs roof sheathing that is at least 3/4 inch thick, and that the nail must stick out the back side of the sheathing at least a tiny little bit.
So, I think you need 3/4 inch plywood or solid board roof sheathing.
Some time ago (a hundred years?) roofing nails did not penetrate the deck. Thicker decks and shorter nails. I remember the difficulty twirling those 1" roofing nails. This had two benefits: 1) a neater looking attic, and 2) no condensing or frosting points. The downside, I think, is that the shrink-swell process in wood that "walks" the nail out of the deck can happen more easily.
I've had historic jobs where I requested clipping the protruding nails with a bolt cutter.
Just for clarification: The roof is done, and the 1/2" OSB assumption was a worst case. If the sheathing is actually 3/4", then I should be able to cut the nails off flush per the specification. The question was whether any cutting of the nails would cause a problem as long as I complied with the 3/4" in the original specification.
David,
I'm confused. If the roof is done, you should be able to answer the question of whether the building has 1/2-inch roof sheathing or 3/4-inch roof sheathing.
The question is whether cutting the nails will be a problem as long as I leave >=3/4" penetration after doing so.
David,
“When fasteners do not penetrate the deck at least 3/4” or all the way through thinner panels, the likelihood of nails backing out, or coming loose, is very high” Minimum nailing base should be 3/8” plywood or 7/16” OSB… If you are worried about condensation on the nails, then you should install a double-decker with rigid foam in the middle.
What does your shingle manufacturer’s installation instructions say? What shingles are you installing?
Armando,
If the manual calls for a "minimum penetration of a roofing nail into roof sheathing" of 3/4 inch, why do you write that "Minimum nailing base should be 3/8” plywood"?
Martin,
If you are using roof sheathing that is 3/4" or thicker, then the nail must penetrate 3/4" min. into the sheathing. If you are using an approved roof sheathing that is less than 3/4", like 7/16 OSB or 3/8" plywood, then the nail must go all the way through. They do specify the shank to be 11-12 gauge, the head diameter to be st least 3/8”, but no specs on how long the shaft needs to be after passes through a 7/16” or 3/8” sheathing.
I do think it can be confusing the way their installation manual is written. I've contacted CertainTeed tech support and asked if they could answer this thread, hopefully they do.