Foam strips as furring for rain screen.
I’m looking at the different solutions to fasten 2″ foam to zip sheathing and studs, followed by a rain screen and corrugated metal siding.
I see that the most common practice is to use 1×3(or 4) wooden furring strips to secure the foam to the studs, and then the siding screwed to the furring strips. fastener type and length can be determined by one of these tables:
What I’m wondering is the possibility of replacing the wooden furring strips with strips of 1/2″ foam. In effect, that would be fastening the siding directly through 2.5″ of foam into the studs. One would need a 4″ screw to achieve 1.5″ of penetration into the studs, likely a #10 x4″. Securing siding directly through foam of varying thicknesses into studs (without wooden furring) is documented in the above article. So has anyone done this and is this a bad idea?
I’ll be running corrugated metal siding horizontally, so I’ll need vertical furring. The fact is that the quality and cost of lumber is going through the roof and a piece of 1×4 at for example home depot is $5 a piece! If strips of polysio or XPS can be used to create this rainscreen gap, it’d be a fraction of the cost (4×8 1/2″ is $13, which can make 16 strips of 3″ wide foam furring). Cutting it will be a pain, and holding the foam/foam strips up before the siding gets screwed through will be a bit fiddly and probably need some capped screws.
Benefits other than material cost include actually more overall insulation, and not having to worry about the wood strips splitting during installation (likely) and deteriorating over time because its thin and not treated.
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