Fastening Furring Strips to a Foam-Sheathed Wall

first_img Start Free Trial Already a member? Log in UPDATED March 1, 2012If you’re building a house with foam sheathing, and your siding is installed over vertical rainscreen strapping installed on top of the foam, how should you attach the strapping? Most builders screw the strapping through the foam into the studs; so far, so good. But what length screws should you use? And how closely should you space the screws?Answers to these questions can be found in a new technical bulletin published by FastenMaster, the company that manufactures Headlok screws. The bulletin, “Attaching Exterior Wall Covering Assemblies with Foam Sheathing to Wood Wall Framing,” is available from FastenMaster.If you follow FastenMaster’s prescriptive recommendations, your furring strips will adequately support the weight of the siding and will secure the furring strips to the wall in a way that resists wind and seismic forces.First, the basics:I have prepared two tables that incorporate FastenMaster’s recommendations. (My tables are more logical and easier to read than the table in the FastenMaster document, shown as Illustration 2, below.)The first table below is for houses with studs spaced 16 in. on center; the second is for houses with studs spaced 24 in. on center.Table 1 notes:Fasteners spaced 24 inches apart give you an allowable design wind pressure of 49 psf.Fasteners spaced 16 inches apart give you an allowable design wind pressure of 73 psf.Fasteners spaced 12 inches apart give you an allowable design wind pressure of 98 psf.Fasteners spaced 8 inches apart give you an allowable design wind pressure of 147 psf.Table 2 notes:Fasteners spaced 24 inches apart give you an allowable design wind pressure of 33 psf.Fasteners spaced 16 inches apart give you an allowable design wind pressure of 49 psf.Fasteners spaced 12 inches apart give you an allowable design wind pressure of 65 psf.Fasteners spaced 8 inches apart give you an allowable design wind… Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and construction details.center_img This article is only available to GBA Prime Memberslast_img

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