How do I fix a deck that is pulling away from the house in Saint John NB?

A deck pulling away from the house is a failed ledger board connection, and it is the single most dangerous structural defect a deck can have because it risks sudden catastrophic collapse. This is not a cosmetic issue or a gradual maintenance concern. In Saint John, where decks are often elevated due to the city's hilly terrain, a ledger failure can mean a fall of 8 to 15 feet or more, causing serious injury or death. Treat this as an emergency and restrict access to the deck until the repair is completed.

The ledger board is the horizontal framing member that attaches the deck to the house's rim joist or band board. It carries roughly half the total weight of the deck, including all live loads from people, furniture, and snow. When the connection fails, the deck pivots downward away from the house like a hinge, and the collapse happens with almost no warning.

In Saint John's Maritime climate, ledger failures happen for specific reasons. The number one cause is missing or deteriorated flashing. Without proper flashing above the ledger, rain and snowmelt run down the house wall and into the gap between the ledger and the house sheathing. Saint John receives approximately 1,400 mm of precipitation annually, and that water rots the house rim joist, the ledger board, or both, weakening the wood that the fasteners grip into. After 10 to 15 years of this hidden moisture intrusion, the wood becomes so soft that the lag bolts or screws simply pull through.

The second common cause is inadequate original fastening. Many older Saint John decks were attached with nails or with lag bolts that were too short, too few, or improperly spaced. The National Building Code requires 1/2-inch diameter lag bolts or through-bolts in a specific staggered pattern, typically at 16-inch intervals, penetrating through the ledger, through the house sheathing, and solidly into the rim joist.

To repair the connection, start by temporarily supporting the deck with adjustable jack posts or heavy-duty temporary posts placed close to the house, transferring the load to the ground. With the deck supported, remove the old fasteners and pull the ledger away enough to inspect the house rim joist behind it. If the rim joist is rotted, it must be replaced or reinforced with new lumber sistered alongside it from inside the basement or crawl space. There is no shortcut here; driving new bolts into rotten wood will fail again.

Once the rim joist is confirmed solid, reattach the ledger using 1/2-inch diameter hot-dipped galvanized or stainless steel lag bolts, at least 4 inches long, in a staggered pattern every 16 inches. Each bolt should have a washer, and pilot holes must be drilled to prevent splitting. Before final tightening, install self-adhesive flashing membrane over the top of the ledger and up the wall at least 6 inches, lapping under the house siding or cladding so water is directed outward rather than behind the ledger.

Given Saint John's exposure to Fundy-driven weather and the serious safety implications of a ledger failure, this repair should be inspected by a qualified professional. If your deck is more than one storey above grade, New Brunswick building code requires a permit for structural deck repairs, and the inspection provides documentation that the work meets code requirements.

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