Secure polyiso temporarily to roof deck, nails or screws?
DamionL
| Posted in General Questions on
Hi all, curious what you normally use to secure polyiso to a steep roof deck? Are cap nails strong enough or are screws with special spacers better?
How far embedment past the bottom of the plywood deck is recommended? For example, if securing 2″ of polyiso onto a 1/2″ cdx roof deck, how long should the screws or nails be?
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Replies
Foam screws are cheap. 500 to a bucket What do you mean by temporary?
Temporarily because the upper layer of plywood with lag screws will ultimately secure everything together. Typically cap nails and screws penetrate the underside of the roof deck by 1/2” or so, is this needed or will the foam hold if the nails/screws are exactly as long as the foam + plywood roof deck? I’d hate to secure all the foam and lose it to the wind overnight!
verify if you can get your values with 1/2" sheathing. 5/8 or 3/4 is more common for fastening when screws don't go into framing.
8 EA #12 screws with 2" screw plates and 3/4" min depth sticking out the bottom for each full sheet would be more than plenty, especially since the common fastening of the subsequent layers will hold things down more.
i would not rely on cap-nails.