Q21) According to Murus the SIP panel manufacture that is spec’d per drawing set they do not offer a T&G fir board finish sheathing. They offer a Eastern White Pine but he advised that it would be better to put down T&G boards first to improve the overall finish and installation speed. What type and size of T&G material should be used here?

Answer: The T&G boarding shall be installed over the rafters. The spec. for the boarding is 1×6 v-groove T&G Knotty appearance grade Douglas Fir. The boarding shall be covered with 15# roofing felt prior to installation of the SIPS panels. The SIPS panels are installed directly over the felt and boarding, with fasteners penetrating through the boarding and into the rafters. Where the SIPS panels cantilever beyond the rafters, the boarding shall also be fastened to the underside of the SIPS panels using 2” 15 gauge finish nails.

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