What Happens If You Build a Deck Without a Permit in Ontario?

Maybe you built the deck. Maybe you bought the house and inherited it, along with three paint cans and a mystery key. Either way, an unpermitted deck is a building question, not a confession-writing contest. Start with facts.

First, confirm that a permit was required

Permit triggers vary by municipality and deck configuration. Attachment to the house, area, height above grade, guards, roof structures, and zoning can all matter. Check the municipal building department and read our Ontario deck permit guide before assuming that small means exempt.

What can the municipality do?

Ontario's current building-permit guide says building without a required permit is an offence and explains that municipal officials can use enforcement orders. Under the Building Code Act, an inspector may order concealed work uncovered at the responsible person's expense when it was built without a permit and needs inspection.

• A stop-work or compliance order
• Drawings and a permit application for the existing deck
• Access to inspect footings, framing, ledger, guards, and stairs
• Corrections where the deck does not meet accepted plans or code
• Prosecution and fines in serious or unresolved cases

The safest order for an existing deck

1. Search the municipal property and permit records.
2. Photograph the full deck, height, house connection, framing, footings, guards, stairs, and visible defects.
3. Contact the local building department and describe the deck honestly.
4. Ask whether a designer or engineer must document the existing construction.
5. Apply using the municipality's requested process and keep work exposed for inspection.
6. Complete corrections and obtain written final status.

Will the deck have to be demolished?

Not automatically. The answer depends on zoning, structure, safety, available evidence, and whether defects can be corrected. A deck in a prohibited setback is a different problem from a sound deck with missing paperwork. The building department decides what it can accept; a contractor cannot pre-approve the answer from the driveway.

If movement, rot, loose guards, failed stairs, or a wet ledger is visible, restrict access until it is assessed. Our ledger flashing guide and Ontario railing guide explain two common safety and durability checks. Paperwork matters. Gravity has its own department.