If your deck attaches to the house, the ledger is where safety is won or lost. A properly bolted, flashed ledger lasts decades; a nailed or un-flashed one rots the house framing or tears off under a crowd. Below we answer the eight attachment questions homeowners ask most. This page is part of our complete guide to building a deck in Ontario.

Attaching the ledger so the house doesn’t rot

How do I attach the ledger so the house doesn’t rot behind it?

Bolt the ledger to the house’s rim joist through the sheathing — never to siding or brick veneer — and flash it so water can’t sit behind it. Lay a peel-and-stick membrane on the sheathing first, fasten with hot-dip galvanized or approved structural hardware, then cap the top with metal flashing tucked under the housewrap.

The enemy is trapped water. In Ontario’s freeze-thaw climate, moisture behind an un-flashed ledger soaks the rim joist, freezes, and rots the connection from the inside out — often invisibly for years. Bolting into solid framing handles the load; flashing handles the water. You need both. The same logic carries up into the deck framing that the ledger feeds.

What’s the correct flashing detail and layer order?

Water has to shed outward at every layer. The sequence matters: housewrap on the sheathing, a self-adhered membrane where the ledger lands, the ledger bolted tight, then Z-flashing over the ledger’s top edge tucked behind the housewrap and siding above. Caulk is not flashing — it fails in a few seasons.

1. Sheathing + housewrap: the wall’s existing weather barrier, lapped so upper layers cover lower ones.
2. Self-adhered membrane: a peel-and-stick strip on the sheathing where the ledger sits, so any bolt penetrations are sealed.
3. The ledger: bolted tight to the rim joist, often on small spacers/washers so water can drain behind it.
4. Z-flashing (cap flashing): metal over the top edge of the ledger, slid up under the housewrap/siding so water runs out over the ledger, never behind it.

Fasteners, brick and freestanding

Lag bolts vs through-bolts vs structural screws — what spacing?

Through-bolts are strongest; approved structural screws are code-accepted and easiest to install; plain lag screws are the minimum and must fully bite the rim joist. Stagger two rows and space fasteners roughly every 16 inches, kept back from the board ends and edges. Use only hot-dip galvanized or stainless hardware against treated lumber.

Whatever you choose, the fastener has to land in solid structural framing — the rim joist or blocking — not just the sheathing. Match every connector, washer, and bolt to treated-lumber-rated metal, because standard zinc corrodes fast against modern pressure-treated wood and can fail at the connection.

Can I attach a ledger to brick or brick veneer?

No. Brick veneer is a cladding, not structure, and won’t hold a deck. You either remove the veneer and bolt through to the framing with a proper standoff detail, or you skip attaching entirely and build a freestanding deck. Bolting a ledger to brick veneer is one of the most common causes of deck collapses.

The brick you see on most Ontario homes is a single decorative wythe tied loosely to the framing behind it — it can’t carry the pull-out and downward loads a deck puts on a ledger. Solid masonry walls are different and may allow a designed connection, but for typical veneer, freestanding is the safe, simple answer.

Attached vs freestanding — which is safer?

Both are safe when built right, but freestanding removes the riskiest detail — the ledger — entirely. If your wall is brick, the framing is questionable, or you can’t flash it properly, go freestanding: it adds one beam-and-post line but eliminates the rot-and-pull-away failure mode. Attached decks save space but demand a flawless ledger.

Lateral loads, tricky walls and old ledgers

Do I need lateral-load (hold-down) connectors?

Often yes. Many Ontario municipalities now require lateral-load (hold-down) connectors that tie the deck joists back into the house’s floor framing, because ledger bolts alone resist pull-away poorly. They’re inexpensive tension ties installed in pairs. Confirm your town’s requirement — and remember that going freestanding avoids this detail altogether.

Can I attach to a cantilevered floor or bump-out?

Generally no. A cantilevered floor or bump-out isn’t designed to carry a deck’s pull-out and downward loads, so you can’t safely hang a ledger off it. Build that side freestanding with its own beam and posts, or have an engineer design a connection. Don’t bolt a ledger to an overhang and hope.

My old deck’s ledger is just nailed on — is it dangerous?

Yes — a nailed-on ledger is a known collapse risk and should be fixed now. Nails pull straight out under load, and most deck collapses start at the ledger. Add proper bolts or structural screws into the rim joist, check for hidden rot behind it, and add flashing. If you can’t confirm solid framing behind it, convert the deck to freestanding.

Frequently asked questions