How do I attach a deck ledger to the house?

Use ½-inch lag screws or through-bolts spaced per Table R507.2 into a solid band joist — never nails — with proper flashing (IRC R507.2).

A deck ledger carrying up to 50 psf must be fastened to a 2-inch nominal band joist with ½-inch lag screws or bolts and washers, spaced according to Table R507.2 (spacing varies with the joist span). The ledger itself should be at least a 2x8 of pressure-preservative-treated lumber.

Nails and ordinary deck screws are not permitted for the ledger-to-band-joist connection. Fasteners must be hot-dipped galvanized or stainless steel, and lag screw tips must fully extend past the inside face of the band joist.

Flash the ledger per Section R703.4 so water cannot reach the house rim. The ledger also may not be attached over exterior veneer such as brick or stucco.