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Attaching siding through rigid foam

joenorm | Posted in General Questions on

I plan to wrap my building in 1 inch EPS. Part of the reason I am choosing 1 inch is in an attempt to save myself from overly complex detailing associated with thicker layers of foam. 

Siding will be a combo of reverse board and batten and corrugated metal oriented vertically. I like these two siding choices because they inherently provide an air gap without having to add during strips.

My question is about attachment through the foam. Is it sufficient to just get a little longer fasteners and attach like I would without foam? For the board and batt I would use a stainless ring shank nail and for the metal I would of course use a gasket screw. The concern is the the foam layer not being structural and allowing the siding to sag or something. Seems unlikely but I know a lot of people here have experience with these details.


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  1. GBA Editor
    Brian Pontolilo | | #1


    The IRC specifies 1 1/4 inch fastener penetration for wood siding installed over rigid foam insulation without furring strips. For other siding types the IRC calls for either following manufacturers' instructions or an "...approved design for support of cladding weight," which would require some engineering help. You should discuss this with your building inspector to make sure they are happy with your approach.

    I'm not exactly sure how "reverse board and batten" is different than vertical wood siding over furring strips, which is essentially a rainscreen siding install, but nevertheless, the same section of the code specifies fastener details for that as well. You can find it all here:

    If you do go with the "reverse board and batten" siding, you'll need to incorporate other rainscreen specifics, like screens to keep pests out and flashing details unique flashing detials. Here's an article that may be helpful:

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