Composite vs Pressure-Treated Decking: Which Should You Build in Ontario?
A practical Ontario homeowner's guide comparing composite and PT decking — cost, lifespan, maintenance, look and resale value.
Choosing between composite and pressure-treated (PT) lumber is the single biggest decision most Ontario homeowners make when building a deck. The two materials look similar from a distance — but they live very different lives. After 500+ builds across London, Woodstock, St. Thomas and the surrounding area, here's the honest breakdown we give every client.
The 30-second answer
Pressure-treated is roughly 40–50% cheaper up front, but needs sealing or staining every 2–3 years to last. Composite costs more up front but is nearly maintenance-free for 25+ years — and most homeowners come out ahead on lifetime cost.
What is pressure-treated lumber, exactly?
Pressure-treated lumber is softwood (typically southern yellow pine or spruce) that's been chemically treated to resist rot, fungi and insects. In Canada, the chemical of choice is now ACQ (alkaline copper quaternary) — safer than older CCA treatments and approved for residential use.
- Cost: roughly $4–$7 per square foot of decking material
- Lifespan: 10–15 years with proper maintenance, 20+ with annual care
- Maintenance: stain or seal every 2–3 years; occasional board replacement
- Look: classic wood grain, ages to silvery grey if left unsealed
What is composite decking?
Composite decking is engineered from recycled wood fibres and recycled plastic, typically wrapped in a polymer shell ("capped composite"). Modern brands like Trex, TimberTech, MoistureShield and Fiberon now closely mimic the look of stained hardwood — but never need staining, won't splinter, and resist fading.
- Cost: roughly $10–$18 per square foot of decking material
- Lifespan: 25–30 years; many brands offer 25-year warranties
- Maintenance: occasional wash with soap and water — that's it
- Look: factory-finished, consistent colour, slip-resistant
Total cost over 20 years (a real Ontario example)
For a 400 sq ft deck in London, here's the actual cost we tracked over 20 years on two side-by-side builds (one PT, one composite):
- PT deck — build cost: $11,500 in 2026 dollars
- PT deck — 20-year maintenance: $4,800 (staining/sealing every 2.5 yrs, two board replacements)
- PT deck — total at 20 yrs: ~$16,300, and the deck is at end of life
- Composite deck — build cost: $18,400 in 2026 dollars
- Composite deck — 20-year maintenance: $400 (wash kit + minor repairs)
- Composite deck — total at 20 yrs: ~$18,800, and the deck has 5–10 years left
When PT still makes the most sense
- Tight budget, or you plan to move within 5 years
- You actually enjoy the look of natural wood and don't mind staining
- The deck is small enough that maintenance is trivial
- You want a rustic, cottage-style look that ages to a grey patina
When composite is the obvious winner
- You're staying in the home long-term (10+ years)
- You hate maintenance, or live somewhere where staining is a hassle
- The deck gets heavy sun exposure — composite resists UV fading better
- You want a polished, modern look to lift resale value
What we actually recommend in Ontario
For most clients in London, Woodstock or St. Thomas planning to stay 7+ years, we recommend composite. For shorter-term owners or smaller decks under 200 sq ft, PT is hard to beat. We'll quote both side-by-side for free — it's the easiest way to compare.