Deck Ledger Board Attachment Done Right

Most catastrophic deck failures aren't the joists or the beam — they're the ledger pulling away from the house. The ledger is the board that bolts the deck to the building, and it carries half the deck's load straight into the wall framing.

Fasteners, not nails

The IRC (R507.9) requires a specific pattern of lag screws or through-bolts into the house's band joist — never nails, and never into just the sheathing. The bolt spacing depends on the joist span the ledger carries; longer joists put the bolts closer together.

Flashing is not optional

• Water trapped behind a ledger rots the band joist until the bolts have nothing to hold.
• Flash over the top of the ledger and integrate it with the house's water-resistive barrier.
• Leave a small gap so water drains rather than wicking into the connection.

When to go free-standing

If the band joist is questionable — engineered I-joists, a cantilevered floor, brick veneer, or stucco — a free-standing deck with its own beam and posts on the house side sidesteps the ledger problem entirely. It costs a little more in footings but removes the single biggest failure mode.