Key Takeaways:
- A DIY deck build takes 2–4 weekends for an experienced handyperson
- Always get a building permit before starting — required for decks 24"+ above grade
- Footings must extend below the frost line (4–6 feet in most of Canada)
- Materials for a 300 sq ft PT wood deck cost approximately $2,500–$4,500
- The ledger board connection to the house is the most critical structural detail — do this wrong and the deck can collapse
Step-by-Step Overview
Step 1: Design and Permits
Decide on size, shape, height, and material. Draw a site plan showing the deck's position relative to the house, property lines, and setbacks. Submit for a building permit ($200–$500, 2–6 weeks processing).
Step 2: Layout and Footings
Mark footing locations using batter boards and string lines. Dig below the frost line — 1.2–1.8m depending on your region. Install sono tubes or helical piles. Schedule footing inspection before pouring concrete.
Step 3: Posts and Beams
Set 6×6 pressure-treated posts in post brackets on footings. Level and plumb each post. Install doubled 2×8 or 2×10 beams on top of posts using through-bolts (not just nails).
Step 4: Ledger Board
The most critical step. The ledger board connects the deck to the house. It must be through-bolted to the rim joist with 1/2" lag screws or through-bolts at 16" on-centre. Install self-adhering flashing membrane behind and over the ledger to prevent water from entering the house wall. Failure at the ledger connection is the #1 cause of deck collapse in Canada.
Step 5: Joists
Hang joists from the ledger board and beam using Simpson Strong-Tie joist hangers (CSA A370 compliant). Standard spacing is 16" on-centre for wood boards or 12" on-centre for composite (check manufacturer specs). Install blocking between joists at 8-foot intervals for lateral stability.
Step 6: Decking
Install deck boards perpendicular to joists using appropriate fasteners. Leave 1/8" gap between boards for drainage and expansion. If using composite, follow manufacturer gapping instructions exactly — typically 3mm side gap and 6mm end gap.
Step 7: Railings and Stairs
Install code-compliant railings (42" height, 4" max baluster spacing). Build stairs with consistent rise (max 7.75") and run (min 10"). Schedule final inspection.
DIY vs Hiring a Contractor
| Factor | DIY | Contractor |
|---|---|---|
| Cost (300 sq ft PT wood) | $2,500–$4,500 materials | $6,000–$12,000 total |
| Time | 2–4 weekends | 3–5 days |
| Quality | Variable — depends on skill | Consistent — experienced |
| Permit responsibility | You pull the permit | Usually contractor pulls |
| Warranty | None | Workmanship warranty |
