The Deck Permit Guide for London, Ontario (2026)
Everything you need to know about deck permits in London, Middlesex County and Elgin County — when you need one, how to get one, and what inspectors actually check.
Most homeowners in Southwestern Ontario need a building permit for any deck more than 24" (600 mm) above grade — but the rules vary by municipality. This guide covers London, Middlesex County and Elgin County. We pull permits for our clients as part of the build, but it's good to know what's going on behind the scenes.
When you need a permit in London, Ontario
- Decks over 600 mm (24") high: permit required
- Decks attached to your house: permit required regardless of height (ledger flashing is inspected)
- Roofed or covered decks: permit required, plus structural review
- Decks under 600 mm and detached: usually no permit, but zoning setbacks still apply
If you're in St. Thomas, Strathroy-Caradoc, Woodstock, Tillsonburg or any of the other surrounding municipalities, the rules are similar — but always confirm with the local building department.
What inspectors actually check
Inspectors don't show up to admire the finish — they're looking for safety. Specifically:
- Footings: sized correctly (typically 10–12" diameter) and below frost line (1.2 m / 4 ft in Ontario)
- Ledger board: properly bolted to the house with structural lag screws, flashing in place to keep water out
- Beam and joist spans: consistent with OBC tables
- Railings: 36" min for decks under 5'11" above grade, 42" for higher decks; balusters max 4" apart
- Stair geometry: consistent rise/run, graspable handrail
Typical permit timeline
- Plan preparation: 3–5 business days (we handle this)
- Permit submission to review: 1–2 weeks in London
- Construction inspection: footings inspected after digging, framing inspected before decking goes on, final inspection at completion
Cost of a deck permit
In London, deck permit fees are typically $150–$350 depending on the deck size and complexity. In St. Thomas and Strathroy-Caradoc, fees usually fall in the $120–$280 range. We include the permit fee in our quote so there are no surprises.
What happens if you skip the permit
A few real consequences we've seen:
- Forced removal of the deck if a complaint is filed (rare, but it happens)
- Failed home inspection on resale — buyers often walk away or demand a price cut
- Insurance claims denied if injury occurs on an unpermitted structure
- Retroactive permit fees, typically double the original
We handle the permit for you
Permit hassles are why a lot of homeowners hire us. We draw the plans, submit them, schedule the inspections, and meet the inspector on-site. You just sign the forms.