Deck staining service in Markham: sealing and waterproofing

A wooden deck in the GTA takes a beating. Summer sun bleaches it, snow and rain sit on it for months, and every soak and dry-out makes the boards swell and shrink.

After a few years the boards go grey and the old finish flakes off. Usually the wood underneath is still sound, so a proper clean, a few repairs and a new coat are enough. That’s the work our deck staining service covers in Markham and nearby.

Sun and water on unprotected wood cause most of it. Sunlight breaks down the surface and turns it grey, as the University of Missouri Extension explains.

The USDA Forest Products Laboratory links the swelling and shrinking from rain to cracks, raised grain and mildew. A good finish slows both down.

What people usually notice first:

• The deck looked great when it was built and now it’s grey and patchy.
• Paint from the last refresh is peeling off in strips.
• Black or green spots in shady corners won’t come off with the hose.
• The kids keep getting slivers from the stairs.

The steps are much the same for a small back porch or a two-level deck:

1. We look over the boards, stairs, railings and the old finish.
2. We pressure wash the whole deck to lift dirt, mildew, loose wood fibres and finish that’s already coming off. The Forest Products Laboratory warns that power washing can strip wood from the surface, so the pressure and nozzle are set for wood (more in pressure washing decks without damage).
3. We fix or replace loose, cracked or rotten boards and popped nails or screws. That side of the job is on the deck and fence repair page.
4. We let the wood dry right through. A finish on damp wood may not soak in or bond, so this step sets the schedule.
5. We put on paint or a waterproof coating a few boards at a time along their full length, then do the stairs and railings. PPG’s label says to work this way to avoid lap marks.

You can see a deck we took from grey to a warm cedar tone with pressure washing and a waterproof coating on the deck restoration project page.

For the floor boards, a penetrating coating usually holds up better than paint. The Forest Products Laboratory recommends penetrating finishes for deck floors, because paint and solid stain wear through where people walk, trap moisture and peel.

Scroll sideways to see the whole table.

Water repellents and semi-transparent stains are both penetrating coatings. Neither can soak through paint, so a painted deck usually stays painted unless it’s stripped back to bare wood first.

The deck staining guide goes through the product choices in more detail. Deck sealer vs stain vs waterproofing explains what a clear sealer or waterproofing product actually does.

We quote every deck after seeing it, because its condition moves the price more than the stain does. Peeling paint, repairs and lots of stairs or spindles all add time.

For a rough idea, HomeAdvisor’s 2026 cost guide puts professional deck staining at US$550 to $1,250. Those are American figures, so convert them and add 13% HST for a GTA deck.

For per-square-foot ranges and worked examples by deck size, see how much deck staining costs.

Late spring to early fall, on a run of dry days. Coatings need dry wood and mild weather, and the product labels set the limits:

Scroll sideways to see the whole table.

If you want the deck done before summer, ask for a quote in spring. Early fall works when there are a few dry days in a row, but cold nights and morning dew make late fall hard around Markham.

Sweep often so leaves don’t sit wet on the boards, and move planters and mats now and then.

Each spring, sprinkle water on the busiest boards. Once it soaks in instead of beading, plan another coat.

A small, sound deck is a fair DIY job if you have a few clear weekends and patience for the prep.

Most DIY trouble comes from rushing: coating wood that’s still damp from washing, putting on too thick a coat (Benjamin Moore warns excess stain won’t cure properly), or painting over loose old finish. That’s usually why a new finish peels or goes blotchy early.

Hiring makes more sense for big decks, long stairs and railings, or peeling paint that has to come off first.

Yes. We work across Markham and nearby, including Richmond Hill, Thornhill and Stouffville.

If the fence needs the same treatment, see fence painting and staining. Our comparison of fence painting vs staining covers which finish suits it.

To start, text a few photos of the deck to (437) 684-2535 with your street or postal code. We’ll arrange a time to come and look, and give you a free quote.

• Boards that have gone silver-grey or blotchy
• Water soaks into the wood instead of beading on top
• Old paint or finish peeling off in strips
• Splinters or rough, fuzzy patches on the boards
• Green or black mildew in shady corners
• Railings and stairs that look worse than the rest of the house