What are the NB Building Code fire separation requirements between a garage and a deck?

There are no fire separation requirements in the NB Building Code specifically between a garage and an adjacent deck. Fire separation requirements apply to the boundary between the garage and the interior living space of the dwelling — not between the garage and an exterior structure like a deck.

That said, the relationship between a garage, a deck, and the house involves several code and practical considerations worth understanding clearly.

Where Fire Separation Actually Applies

The NB Building Code (following the National Building Code framework) requires a minimum 45-minute fire-resistance rating on the wall and ceiling assembly separating an attached garage from any habitable space inside the house. This means 5/8-inch Type X fire-rated drywall on the garage side of all common walls and ceilings, with taped and finished joints. The door connecting the garage to the house must be a solid-core door at minimum 1-3/4 inches thick (or a rated 20-minute fire door), with a self-closing device and proper weatherstripping.

This assembly exists because garages store flammable materials — gasoline, solvents, propane — and house vehicles with fuel systems. The fire separation buys occupants time to escape if a garage fire ignites.

Where a Deck Complicates Things

The scenario that does raise code concerns is when a deck is attached to the house and positioned adjacent to or above the garage, in a way that a deck door or window opens into a space that shares a wall with the garage. If that deck door leads into a room that is part of the fire-separated zone — say, a mudroom or hallway that connects to the garage — the fire separation integrity of that entire assembly needs to be maintained. Penetrations, doors, and openings in the fire-rated assembly must be properly protected regardless of what is on the other side.

Another situation worth flagging: if a deck is built over an attached garage roof, the garage ceiling below still requires its fire-rated assembly. The deck above does not change that requirement, and the structural connection between the deck and the garage must not compromise the fire-rated ceiling assembly beneath.

Practical Considerations for Garage-Adjacent Decks

Even without a specific fire separation requirement between garage and deck, there are practical building and safety considerations. Decks built directly adjacent to garage walls should maintain clearance from any garage vents or exhaust openings, since vehicle exhaust or fumes from stored materials can accumulate in the space beneath a deck. This is a ventilation and carbon monoxide concern more than a code-driven fire separation issue.

Deck ledger attachment to a garage wall also requires attention — the ledger must be fastened into structural framing, and any penetrations through the garage's exterior wall sheathing and weather-resistive barrier must be properly flashed to prevent water infiltration. In NB's wet Maritime climate, a poorly flashed deck ledger against a garage wall is a reliable path to rot and structural deterioration within a decade.

The Bottom Line

If you are building an attached garage with a deck nearby or connected to the same structure, the key questions for your building inspector are: Does the deck create any new openings or penetrations in the fire-rated assembly between the garage and the living space? Does the deck ledger attachment compromise the structural or moisture performance of the garage wall? Those are the details that matter.

For anything involving the fire separation assembly itself — drywall type, door specifications, fire-stopping of penetrations — hire a professional and have the work inspected. This is a life-safety system, and it needs to be done correctly.

If you are planning an attached garage addition and want to connect with a contractor experienced in NB building code requirements, New Brunswick Garages can match you with local builders through the New Brunswick Construction Network at newbrunswickconstructionnetwork.com.