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vinyl siding and furring strips

Shaun A | Posted in General Questions on

I have a wall assembly that consists of 7/16 zip, 3″ of mineral wool, 3/4″ furring strips, and vinyl siding. My siding guy will not install b/c he says 3/4″ is not enough nailing depth and he needs a min of 1 1/4″. What can I show him that will support my install method? Of course he has never seen a wall assembly with exterior insulation and rain screen before.

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  1. Steve Knapp CZ 3A Georgia | | #1


    What does the siding manufacturer advise?

    FWIW. When I had one-inch furring strips installed on my last home, they were aligned with the framing. That was necessary to handle the weight of the cement siding.

    1. Shaun A | | #2

      I will check with the manufacturer. My furring strips will be screwed 16 inches on center up each stud with a 5 1/2 inch lag screw

  2. Burninate | | #3

    Vinyl siding is built with a substantial degree of cross-ventilation; Most people seem to consider it "almost as good as a vented rainscreen" when installed normally. suggests that the furring strips are advised, but that they're more about mechanical support for those nails than about venting:

    Q. "Also, Martin: I was hoping you might elaborate on why vinyl needs a rainscreen when put on top of more than 2 inches of foam. Is because of fastener length? Or some simple practical reason or is it building science based?"

    A. Basically, it has to do with fastener length. Vinyl siding can't be fastened tight to the sheathing -- the fasteners need to be just a little bit loose, so that the siding can expand and contract lengthways to accommodate thermal expansion and contraction. This is hard enough to do when you are installing the product directly over OSB; if you are doing it over 2 inches of foam, it becomes even more challenging. Joe Lstiburek says that 2 inches is the limit before you need vertical furring strips. I might even be more conservative, and limit the thickness of the foam to 1 inch before switching to furring strips.

    From :
    "Still, you’ll want to make sure that the nails you choose are strong enough—and long enough—to keep your siding from lifting off when the wind blows.

    Most builders agree that you should opt for roofing nails for this sort of project. Roofing nails have longer shanks—between one and two inches—and a flatter nail head to keep the material below held securely in place. They’re also extra sharp, so you won’t have to work as hard to nail them in. Most contractors agree that nails used in siding projects should measure at least 1 ½ inches long—or up to 2 ½ inches if you’re installing backerboard with the siding."

    From :
    "Most manufacturers require that nails penetrate at least 3/4 inch into a nailable substrate."
    " straight from the Vinyl Siding Institute's VINYL SIDING INSTALLATION GUIDE, which you can download from their site: - 1-1/2" for general use"

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