Deck permits are the single most misunderstood part of any backyard project. Half the homeowners we talk to think they never need one; the other half think they always do. The real answer is a clear set of thresholds — and getting it wrong costs you at resale.
When you DO need a permit
In most Ontario municipalities, including across the GTA, you need a building permit if your deck meets any of these:
- More than 600mm (about 24 inches) above grade at any point — this is the most common trigger - Attached to the house (ledger-board connection) - Larger than 10 square metres (108 sq ft) in some municipalities - Has a roof, pergola, or is enclosed - Serves a required exit from the home
A standard backyard deck off the kitchen door, raised a couple of feet off the ground and attached to the house, needs a permit in virtually every GTA city. That's the typical project — so assume you need one unless you've confirmed otherwise.
When you DON'T need a permit
You can usually skip the permit for a ground-level platform:
- Under 600mm above grade at every point - Freestanding (not attached to the house) - No roof or enclosure
A low floating deck or a patio-level platform in the backyard often qualifies. But "ground level" is stricter than people think — even a couple of steps usually pushes you over the height threshold.
The rules vary by city — check yours
Toronto, Mississauga, Vaughan, Brampton, and the rest each have slightly different thresholds and setback requirements (how close to the property line you can build). Setbacks are where a lot of decks run into trouble — even a permit-exempt deck has to respect property-line distances and easements.
We confirm the specific requirements for your municipality before quoting any deck project — and we pull the permit when one's needed, as part of the price.
What happens if you skip a required permit
This is the part homeowners underestimate. An unpermitted deck:
- Surfaces at resale. Home inspectors flag attached structures that don't appear in city records. Buyers' lawyers hold back funds or demand you legalize it before closing. - Voids insurance if someone is injured on a non-compliant structure. - Has to be retroactively inspected — and if it wasn't built to code (footing depth, ledger flashing, railing height), you're rebuilding parts of it.
The permit on a typical deck is $200-$600. Legalizing an unpermitted deck after the fact, with retroactive inspection and corrections, routinely runs $3,000-$8,000.
Footings are the hidden code issue
Even with a permit pulled, the most common deck failure is footings that aren't deep enough. In Ontario, deck footings must extend below the frost line — typically 1.2 metres (4 feet) — so the deck doesn't heave every winter. A lowball builder pours shallow footings to save a day of digging, and three winters later your deck is visibly tilting.
We dig every footing to code depth and pass inspection before framing. It's not negotiable — it's the difference between a deck that lasts 25 years and one that fails in 5.
The simple rule
If your deck is attached to the house or more than two feet off the ground anywhere — which describes most real decks — assume you need a permit, and use a builder who pulls it and digs proper footings. Serving deck projects across Toronto, Mississauga, Vaughan, and the GTA.