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Community and Q&A

How to best attach siding through 1.5″ polyiso?

BillWolpert | Posted in Green Building Techniques on

With continuous 1.5″ polyiso over 1/2″ plywood sheathing, can I nail wood siding through the insulation to the studs? I was trying to eliminate another layer of plywood. I am planning to use “Hydrogap” by Benjamin Obdyke and not need furring strips.

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  1. GBA Editor
    Martin Holladay | | #1

    I don't recommend installing wood siding over 1.5 inch rigid foam unless you are also willing to install furring strips to create a generous rainscreen gap.

    You could install your siding with 3-inch nails through the foam into the studs, I suppose, but it's a bad idea. The siding won't dry evenly after it gets wet in a rainstorm, and it may eventually check, cup, or split.

    -- Martin Holladay

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