What screws to use for vinyl siding with 4″ polyiso exterior sheathing?
I’ve put the cart ahead of the horse on a reno I’m doing it seems. I have installed 4″ of polyiso rigid insulation over the exterior of my house and will be covering that with vinyl siding that I already have waiting for install.
The problem I’m having is finding a reasonable priced screw that is Long enough (5″), Exterior grade (aluminum, coated, hot dipped, or even stainless), and with a flat pan head or similar (in order to be low profile enough and not let the vinyl pull out). I will need roughly 2500 screws for this job and spending $1200 or more dollars is outrageous and seems like overkill.
What do the PROS use for this scenario? I know somebody out there has put vinyl over 4″ polyiso.
Thanks a bunch!
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I am doing a similar install on my own house. I have decided to use 6" screws through furring strips into the wall studs and use regular ring shank nails into the furring. The siding manufacturer I used (original siding too) does not warranty this type of install.
The only issue I'm working with is for the starter strip for the siding and the coravent or similar venting on the bottom. The coravent will not hold a nail reliably IMHO and if you don't extend the furring down too the bottom to the wall assembly you may have issues.
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Tim,
Most builders install vertical furring strips if the rigid foam is thicker than 1 1/2 inch. (It's fairly common for builders to install vinyl siding directly on top of rigid foam up to 1 1/2 inch thick.)
Having said that, the Vinyl Siding Institute does not forbid the use of thicker foam under vinyl siding. The VSI Installation Manual notes, "When the fastener must penetrate through a non-nailable material such as foam sheathing, the thickness of that material does not count toward the total. In such cases, the fastener will need to be long enough to penetrate through the non-nailable material and then 1 1/4” (32mm) into wood framing or other nailable material." Nowhere in the manual (as far as I can tell) does the VSI note a maximum foam thickness.
Moreover, there has long been ambiguity and controversy over the best way to install vinyl siding over furring strips. For more information on that issue, see Can Vinyl Siding be Applied Over Furring Strips?
The advantage of installing furring strips is that you will need fewer long screws. For more information on furring strips, see Fastening Furring Strips to a Foam-Sheathed Wall.