How do I know if my deck ledger board is rotting, and how is it fixed?

What the ledger does

The ledger is the board bolted to the house that carries one edge of an attached deck. Half the deck's weight, and everyone on that half, goes through it and its fasteners into the house's rim joist. It is the single most important connection on an attached deck, and it is the one most often built wrong: nailed instead of bolted, bolted into siding instead of framing, or installed without flashing so it quietly rots behind the paint.

Signs from outside

Start at the wall below the deck. Water that gets behind the ledger comes out somewhere, usually as staining, efflorescence, or bubbled paint in a line under the deck. Then look at the ledger itself. A gap between its top edge and the wall, or a ledger that has started to tilt outward, means the fasteners are losing their grip in soft wood. Rust streaks from bolts or lag screws mean they are sitting in wet wood. Mushrooms or dark fungal growth along the bottom edge are a clear call.

Probe the bottom edge and the end grain at each end of the ledger. Probe around each bolt. Push an awl up between the ledger and the siding if there is room; soft wood there is the house rim, not the ledger, and it is the more serious finding.

• Stains or peeling paint on the wall under the deck
• Gap or outward lean at the top of the ledger
• Rusted, weeping, or missing fasteners
• Soft wood at the bottom edge, ends, or around bolts
• Fungal growth or a musty smell at the joint

Why this one matters more than other rot

Deck failures that make the news are very often ledger failures: the connection to the house lets go and the deck swings down. That is partly because the ledger is where water collects and partly because older decks were built before bolting and flashing requirements were enforced the way they are now. An owner who finds a rotted fascia has a maintenance job. An owner who finds a rotted ledger has a safety issue and should keep the crowd off the deck until it is repaired.

How the repair goes

The first row or two of decking comes off so the ledger is exposed. Joist hangers are released and the joists are supported on temporary posts or a temporary beam. The old ledger comes off. Now the house is visible: the rim joist, the sheathing, the building paper. Any rot in the rim gets cut out and repaired; this is where the job can grow, which is why Levi opens this joint early in the scope rather than guessing.

The new ledger is pressure-treated, cut to length, and fastened through the sheathing into the rim with through-bolts or structural lag screws in the pattern the code calls for, never into siding or stucco alone. On a stucco house the stucco is cut back so the ledger bears on solid framing and the flashing can tuck behind the building paper. Flashing goes on top of the ledger, lapped behind the wall barrier and kicked out over the face. Hangers are reinstalled or replaced with hot-dip galvanized or stainless hardware. Then the decking goes back.

Permits and codes

The California Residential Code includes specific requirements for deck ledger fastening, lateral connections, and flashing, and these are the sections a building inspector focuses on. Replacing a ledger may fall under repair or may be treated as structural work depending on the scope; the City of Carlsbad Building Division is the place to confirm what applies before work starts. We state this as general information for homeowners and point you to the official sources rather than guessing on your behalf.

Related questions

Sources and further reading