Decks

Design the layout, choose materials (pressure-treated lumber, cedar, composite, or tropical hardwood), and create drawings showing footing locations, joist spans, beam sizes, guard details, and stair layout. Submit to your municipality for building permit. Include the ledger attachment detail — inspectors look at this closely.

Stake footing locations using string lines squared off the house. Call Ontario One Call to mark buried utilities. Dig footing holes to 4 feet below grade (Ontario frost depth). Footings must sit on undisturbed soil — never on fill or soft ground. Minimum 12-inch diameter for most residential decks, but your permit drawing specifies the size.

Pour concrete into footing forms (Sonotubes or BigFoot systems). Set post bases (like Simpson ABA or PBS) into wet concrete, positioned exactly on layout marks. Level the tops. Inspector checks footing depth and diameter before you pour — don't order concrete until the inspection passes.

Cut and set 6x6 posts (not 4x4 — those are no longer recommended for most applications) on post bases. Install the beam on post caps — never notch a post to receive a beam, as this removes up to two-thirds of the wood and weakens it. Bolt the ledger to the house rim joist using 1/2-inch lag screws or through-bolts at code-specified spacing (Table 2 in DCA 6). Install lateral load connectors (minimum 3,000 lbs total). Hang joists on the beam and ledger using rated joist hangers — nails alone are never acceptable for joist support.

Install flashing between the deck ledger and the house. This is the most critical waterproofing detail on any deck — water getting behind the ledger rots the rim joist and causes the deck to pull away from the house. Use self-adhering membrane behind the ledger, Z-flashing above it, integrated with the house water-resistive barrier. Seal all penetrations. Caulk is not flashing.

Install deck boards perpendicular to joists with 1/8-inch gaps for drainage. Pressure-treated boards should be rated UC4A or better (ground contact rated — this changed in 2016). Pre-drill near ends to prevent splitting. Leave 1/4-inch gap from the house for water drainage. For composite decking, follow manufacturer spacing and fastener requirements exactly.

Build stringers from 2x12 lumber — never smaller. Cut stringer throat must be at least 5 inches deep. Maximum riser height 7-3/4 inches, minimum tread depth 10 inches. No more than 3/8-inch variation between any two risers or treads in the same flight (uneven stairs cause falls). Stringers must be supported at top by stair brackets (not just nails) and at bottom by a concrete landing below frost depth.

Guard posts must be at least 4x4 and bolted through the rim joist with hold-down anchors — never just nailed or screwed. Guards must be 36 inches tall minimum (42 inches in some jurisdictions). Balusters spaced so a 4-inch sphere cannot pass. Stair handrails must be graspable (a flat 2x4 on top of the railing is not graspable) and continuous from top riser to bottom tread. Posts no more than 6 feet apart.

Building inspector checks everything: footing size and depth, ledger bolts and flashing, joist hangers and connectors, guard post attachment, baluster spacing, stair dimensions, and bracing. Fix any deficiencies and re-book if needed. Don't use the deck until it passes.