Building a deck in Ontario is a regulated project. Here is what you need to know before you break ground.
When a Permit is Required
Ontario Building Code requires permits for decks attached to a dwelling, or freestanding decks over 10 sq m (108 sq ft). Permitted decks must meet guard rail height requirements (1,070mm for decks over 600mm above grade) and setback rules.
Zoning Setbacks
Typical Ontario rear/side yard setbacks: 1.2m-1.8m. Toronto has additional rules on rear yard coverage. Check your municipal bylaw before designing.
Material Options
Pressure-treated lumber: $25-$40/sq ft installed. Requires staining every 2-3 years.
Composite decking: $45-$80/sq ft. No staining required. Capped composite resists fading.
Cedar: $35-$60/sq ft. Natural rot resistance but requires sealing.
Structural Details
Ledger board attachment must be properly flashed — the most common source of deck rot failures. Footings must be below Ontario frost depth (1.2m minimum) to prevent heaving.
Costs in GTA
300 sq ft PT lumber deck: $10,000-$15,000 including permits.
300 sq ft composite deck: $18,000-$28,000.
Multi-level with features: $30,000-$80,000+.
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