How do I Mount a Deck Ledger Over Zip System R-Sheathing?
The thickness of the foam insulation will dictate whether you should use a standard fastening schedule or get advice from an engineer.
Dan Crouse, Redding, CA
Editorial adviser Mike Guertin replies: Huber’s Zip System R-Sheathing has rigid-foam insulation bonded to the back side of the structural panel and comes in two product thicknesses: 1 in. and 1-1/2 in. (A thicker version is being developed but isn’t yet available.) The short answer is that if the walls are sheathed with the 1-in.-thick version, you can mount the ledger using the IRC fastener schedule and most major screw manufacturer’s products. This is because the IRC has a maximum 1-in. limit between the back side of the ledger and the face of the rim board.
If the wall is sheathed with the 1-1/2-in.-thick version or the new, even thicker version, you can’t use the prescriptive code table, and your inspector may require that an architect or engineer design an attachment system. If that isn’t a viable option, there is an alternative deck-mounting system. The Maine Deck Bracket costs $29, has an ICC-ESR (meaning it has been tested for code compliance), and works well with thicker sheathing. Because these brackets mount directly to the rim board by way of a hole cut through the wall sheathing, they can accommodate up to 3 in. of thickness.