Pressure-treated (PT) is still the cheapest way to get a real functional deck in front of your back door in the GTA. If your budget is closer to ten thousand dollars than twenty, PT is probably your answer. The catch — and it’s the catch nobody tells you about loud enough at quoting time — is that an unmaintained PT deck in southern Ontario doesn’t last twenty years. It lasts seven, and after that it’s a liability waiting for someone to step through.
A maintained PT deck is a different conversation. Fifteen to twenty years of useful life is realistic, and the maintenance is not complicated. It’s a half-day in the spring and a half-day in late summer, plus a small running budget for stain and fasteners. Below is the realistic month-by-month schedule I’d hand to a family that just had a PT deck installed.
The first 60 days after install
Most contractors will tell you to wait before doing anything to a new PT deck. They’re right. The boards arrive saturated with the pressure-treatment solution (today’s standard is mostly copper azole, MCQ, or ACQ), and they need time to dry to the point where they’ll actually accept a finish. Putting stain on too soon is the most common rookie mistake, and the stain just sits on the surface and peels off in sheets the next spring.
- Days 1–14: nothing. Use the deck. Let it weather.
- Days 15–60:test water absorption every two weeks. Sprinkle water on a board. If it beads, the board isn’t ready. If it soaks in within 30 seconds, you can stain.
In southern Ontario, a deck installed in April or May is usually stain-ready by mid-July. A deck installed in late summer or fall usually has to wait until the following spring — you don’t want to stain right before a freeze cycle.
The annual schedule
Late March / early April: spring assessment
Walk the entire deck. Specifically look for:
- Boards that lifted or cupped over the winter.
- Popped screws or nails that need to be set or replaced.
- Any black staining around fasteners — that’s the chemical reaction between the PT treatment and uncoated steel, and it means a non-galvanized fastener slipped through and needs to come out.
- Soft spots near the ledger or at post bases. Press with a screwdriver tip. Solid wood resists. Soft wood means rot has started.
Most years this assessment finds nothing meaningful. The years it does find something, you want to know about it in April so you can fix it before the season — not in August when you’re actually using the deck.
Late April: clean
A garden-hose rinse first to clear loose debris. Then a deck cleaner appropriate for PT — oxygen-based (like Defy or Olympic) is the safe choice; chlorine-based bleaches damage the wood lignin and lighten the colour permanently. Apply with a garden sprayer, work in with a stiff push-broom, wait the dwell time on the bottle (usually 10–15 minutes), then rinse off.
Total cost: $25–$45 in cleaner. Total time: 2–3 hours for a 200 sq ft deck.
Late May / June: re-stain (every 2–3 years)
Don’t re-stain every year. PT decking generally doesn’t need it that often, and over-staining is what creates the peeling film coat that becomes a real maintenance burden in year five.
Penetrating semi-transparent oil-based stains are the right choice for PT in southern Ontario. Skip the film-forming solid-colour stains unless you specifically want the painted look and you’re willing to re-coat every couple of years. Apply on a dry day, 18–28°C, no rain forecast for 48 hours. One coat is usually enough; flood the wood and back-brush so it absorbs evenly.
Cost: $80–$140 in stain for a 200 sq ft deck. Time: a long afternoon. Frequency: every 2–3 years.
August: mid-season check
Walk the deck again. Quick assessment. Mostly you’re looking for fasteners that worked loose in heat expansion. Tighten or replace as needed. Five-minute job most years.
Late October: pre-winter prep
Sweep the deck completely clean. Remove any planters, furniture cushions, or anything that traps moisture against the boards. Trapped moisture under a flower pot is the single most common cause of localized rot on otherwise well-maintained PT decks.
If your deck has stairs to grade with risers below frost line, take a quick look at where the stair stringers meet the ground — any debris piled against the wood gets cleared. Five-minute job.
The longer-cycle items
Every 5 years: fastener audit
Walk the entire deck with a screwdriver and a box of replacement deck screws (galvanized or stainless, never plain steel). Drive any proud screws flush. Replace any that are corroded or stripped. On a 200 sq ft deck you’re usually replacing 15–30 screws total over the deck’s life. Total cost: $20–$40.
Every 7–10 years: hardware check
Inspect joist hangers, ledger bolts, and post-to-beam connections. Galvanized hangers should still be intact; check for any rust bleeding through the galvanizing. Re-torque any visible lag bolts on the ledger connection. This is the check that catches the problems that matter — a failed ledger connection is the most common cause of deck collapse in residential structures.
Around year 12–15: board-by-board assessment
At this point individual boards may have cupped, cracked, or rotted at the ends. PT board replacement is a one-board-at-a-time job, usually 15–30 minutes per board with basic tools. Budget for replacing 10–20% of the deck boards by year 15. Cost: $4–$7 per linear foot of PT decking plus screws.
What to put in a maintenance log
You don’t need anything fancy. A note on your phone’s calendar each spring works. Track:
- Date of last clean
- Date and product of last stain
- Any boards or fasteners replaced
- Anything you noticed but didn’t fix
The reason to track is that PT deck failures are almost always preceded by warnings the owner forgot they’d noticed. A soft spot in year 7 turns into a cracked board in year 9 turns into the homeowner calling a contractor in year 11.
What this actually costs over 15 years
For a 200 sq ft PT deck in southern Ontario, fully DIY maintained, the running cost over 15 years is roughly:
- Cleaner: $25–$45 per year × 15 = $375–$675
- Stain: $80–$140 every 2–3 years = 5–7 applications × $110 = $550–$770
- Fasteners and incidentals: $40–$80 over the deck’s life
- Board replacement at year 12–15: $400–$700 in material
Call it $1,400–$2,200 across 15 years, plus about 20–25 hours of your time per year. Stretched across 15 years of useful life that’s adding roughly $100–$150 a year to a deck that cost $11,000–$15,000 to install in the first place.
That math is what makes maintained PT still competitive in 2026. Unmaintained PT — the version where the owner ignores all of the above — is the version where the deck rots out in seven years and the “cheap” deck turns out to cost twice the composite that would have lasted thirty.
If you’re weighing the install cost against the long-haul cost, the cedar-vs-composite breakdown runs a similar calculation for upgrade materials. The calculator can give you the per-square-foot range for PT versus the alternatives in your specific city.