In the U.S., decks often collapse when the ledger attachment to the main house fails. In response, codes now require the “positive attachment” detail shown here: a solid connection with closely spaced lag screws (or better yet, bolts).

Pete Sucheski

1. Fasten Securely Space lag screws or bolts in a staggered pattern according to code. Longer joist spans create heavier loads and require closer bolt spacing.

2. Remove Siding Decks must be attached directly to the house sheathing and framing, not fastened through siding or cladding.

3. Install Flashing Rainwater and rot can degrade the strength of the band joist and the deck ledger. Protect this joint from water with careful flashing.