Deck ledger attachment

FastenersR507.9.1.3#

Deck ledgers must be attached to the house with lag screws or through-bolts sized per Table R507.9.1.3(1). Nails are not acceptable as the primary ledger attachment.

Minimum fastener size is 1/2 inch diameter. Fasteners must penetrate the band joist by at least the length required in the table for the deck joist span.

Bolt spacingTable R507.9.1.3(1)#

Bolt spacing is determined by deck joist span and the adopted spacing table. For joist spans up to 6 feet, typical maximum on-center spacing is 30 inches; longer spans require tighter spacing.

Stagger the fastener rows. Two rows, upper and lower, offset so no two adjacent fasteners share a grain line in the band joist.

FlashingR507.9.1.4#

Continuous metal flashing is required between the ledger and the house sheathing, dressed over the top of the ledger and under the water-resistive barrier above. Flashing material must be corrosion-resistant and compatible with the fasteners used.

The flashing must integrate with the weather barrier so water sheds away from the ledger-to-house intersection. Caulk alone is not acceptable in place of flashing.

Band joist condition#

The band joist receiving the ledger must be solid sawn lumber, engineered lumber rated for the use, or concrete/masonry designed to accept the fastener loads. Rim joists of cantilevered floors or floors bearing on engineered I-joists often require additional blocking or a structural modification.

Common inspection flags#

The most common ledger failures on a residential deck inspection:

• Ledger attached with nails or undersized screws instead of lag screws or through-bolts
• Flashing missing or terminating short of the ledger ends
• Caulk used as the weather barrier instead of flashing
• Bolts driven into a band joist that is actually a non-structural rim board
• Stairs and deck corner posts relying on the ledger for lateral support