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· Registered
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Discussion Starter · #1 ·
Up here in Cold Canada a lot of people put vinyl over 2" foam. Gives you a r10.
Now I'm reading about guys that say it will warp if you do this and to use thermowall insulation at the most. What is the best practise?

· Registered User
11,730 Posts
The "drop-in backers" type of foam will buckle the vinyl because most are made of ESP- low density (1/2#) which really moves as it holds the moisture to expand/contract under the vinyl.#6 here;

Perhaps that is what you heard?

Your local code may require 1-1/2" in to solid wood or just 3/4" in to strapping, check with local AHJ. The older IBC required it. 1-1/2" is generally max. thickness (before strapping) because the foam will compress when nailing (hanging) the vinyl and prevent the required expansion/contraction inherent with that product due to temperature changes. Then it will buckle for sure, imperative to hang it on the wall, no tight (touching) nails; This could be the reason you heard about as well, without the backer board, just flat panels. The foam panels move as well, offset the joints with multiple panel, use a WRB over the taped joints/panels. Ask AHJ locally, for best installation.

FYI, the required max. nail shank size for vinyl (pp14) is 1/8" (0.125") shank per manufacturer's link, the 10d (3") shank is a little thicker- (0.1350") so it might void the installation warranty if ever a problem- possible buckling due to nail sides restricting movement in slots... something to think about.

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