Deck Cleaning and Staining: A Complete Ontario Homeowner's Guide

Your deck takes a beating every Ontario winter. By the time May arrives, it's probably grey, cracked, and covered in a winter's worth of mould and mildew. With the right approach, you can restore it to near-new condition — and with proper staining, protect it for years to come. Here's the complete process, done right.

Assess Winter Damage Before You Start Cleaning

Before reaching for the pressure washer, do a thorough walkthrough of your deck. Ontario winters are particularly brutal on wood: the freeze-thaw cycle drives water into wood fibres, which expand and contract repeatedly, causing cracking and splitting. Road salt tracked in on boots accelerates this process by drawing moisture in and increasing the freeze-thaw severity at a microscopic level.

Look for:

• Split or cracked boards: Surface checks (small cracks running with the grain) are normal and cosmetic. Boards split across the grain, or with deep longitudinal cracks that have raised edges, should be replaced before cleaning and staining.
• Soft spots: Press firmly on boards in corners and near the ledger board where the deck attaches to the house. Soft, spongy wood indicates rot. Do not stain over rot — it must be replaced.
• Raised nail heads or popped screws: Freeze-thaw movement pushes fasteners up. Re-drive or replace these before cleaning so they don't create trip hazards or snag stain applicators.
• Greying: Grey wood is weathered and has UV damage. Greying alone is not structural damage — it cleans up well with proper preparation.
• Green or black biological growth: Normal after Ontario's wet fall and winter. Will be addressed in cleaning.

If more than 20% of your deck boards show significant rot or structural damage, it may be more economical to rebuild than to restore. But for most decks in good structural condition, the cleaning and staining process below will produce excellent results.

Pressure Washing Your Deck

The most common deck pressure washing mistake is using too much pressure. Wood is a soft material compared to concrete, and high PSI raises the wood grain, creates fuzzy surface texture, and can permanently scar the boards.

Maximum recommended PSI for wood decks: 1,200–1,500 PSI. Most residential electric pressure washers in this range are suitable. If you're using a gas-powered unit at 3,000 PSI, keep the nozzle at 18–24 inches from the surface and use a 40° tip.

Critical technique rules for wood decks:

• Always spray with the grain, not across it. Spraying across wood grain raises and damages fibres. Follow the length of each board.
• Keep the nozzle moving. Dwelling in one spot even for a few seconds can gouge soft wood.
• Use a 40° or 25° tip — never the 0° or 15° tips on wood.
• Maintain consistent distance — 8–12 inches for most wood decking.
• Work systematically from one end of the deck to the other, doing complete board runs.

Don't forget the deck railings, spindles, and stairs — all of these need cleaning too and often harbour significant biological growth in sheltered areas.

Choosing the Right Deck Cleaning Solution

Plain water pressure washing removes surface dirt but doesn't effectively kill mould and mildew or address the greying caused by UV degradation. A deck cleaning solution is essential for a complete restoration.

Oxygen bleach deck cleaners (sodium percarbonate-based, sold as products like Defy Wood Cleaner or OxiClean Wood Cleaner) are the best choice for most situations. They:

• Kill mould and mildew effectively
• Brighten and restore the natural wood colour
• Are safe for surrounding vegetation when diluted and rinsed
• Don't damage the wood fibres the way chlorine bleach can with repeated use

Chlorine bleach solutions (sodium hypochlorite) kill mould effectively but can weaken wood fibres with repeated use, are harmful to surrounding plants, and don't address the greying/brightening aspect as well as oxygen bleach. Reserve chlorine bleach for severe mould infestations.

Application process: Mix the deck cleaner per the manufacturer's directions. Apply to the wet deck (after a light pre-rinse) with a garden pump sprayer or a low-pressure applicator. Let it dwell 10–15 minutes, scrub with a stiff deck brush in the direction of the grain, then pressure wash off. You'll see the colour change immediately — grey wood brightens dramatically.

For heavily stained or grey decks, a dedicated deck brightener (oxalic acid-based) applied after the cleaner and before the final rinse will restore the wood to near-original colour. This step is optional but produces noticeably better results on weathered wood.

Drying Time Before Staining: The Step Everyone Rushes

This is where most DIY deck staining projects fail. Applying stain to wood that isn't sufficiently dry causes the stain to trap moisture, leading to peeling, bubbling, and a finish that fails within one season.

Minimum drying time after pressure washing: 48–72 hours of dry weather in Kitchener-Waterloo's climate. Many professionals recommend waiting a full week for best results, especially with denser wood species or pressure-treated lumber.

How to test if the wood is dry enough:

• The sprinkle test: Sprinkle a few drops of water on the surface. If the water beads up and sits on the surface, the wood is not ready — it's either still damp or has residual surface tension from previous finish. If the water absorbs quickly into the wood, it's ready to accept stain.
• Moisture meter: For best accuracy, use a pin-type moisture meter. Most stain manufacturers recommend a maximum moisture content of 15–19% for staining. Above this, the stain won't penetrate or adhere properly.
• Visual inspection: The wood should look consistently uniform in colour — not darker in patches, which indicates moisture.

Ontario's spring weather can make this timing tricky. Rain delays are frustrating but necessary — starting with partly dried wood is one of the most common causes of stain failure. Pick a 3-4 day stretch of dry, moderate weather (10–25°C) and be patient.

"The number one call we get about deck staining gone wrong is peeling after one winter. Almost always, the wood wasn't dry enough before staining. You can't rush this step."

— David, D&D Home Services Co-Founder

Stain vs. Paint vs. Sealer: What's Right for Your Deck

Choosing the right finish is as important as proper preparation. Here's a breakdown of your options:

Semi-transparent stain is the most popular choice for Ontario decks and the one we most commonly recommend. It allows the natural wood grain to show through, provides UV protection, and is far easier to recoat in future years than solid stains or paint (which must be fully stripped before recoating).

Oil-based vs. water-based stains: Oil-based stains penetrate deeper into the wood and traditionally provide superior durability, but improved water-based formulas have closed much of this gap. Water-based stains dry faster (important in Ontario's unpredictable spring weather), clean up with water, and have lower VOC content. Either can perform well if applied correctly.

Avoid deck paint on horizontal surfaces (the deck floor). Paint sits on top of wood rather than penetrating it, traps moisture, and peels badly on surfaces that get foot traffic and water pooling. It's also nearly impossible to strip cleanly for recoating.

Stain Application Tips for Ontario Conditions

With the deck cleaned, brightened, and properly dried, you're ready to stain. Here's how to get professional results:

Timing: Apply stain on a day between 10–25°C, out of direct sunlight if possible. Hot direct sun dries the stain too quickly before it can penetrate, leaving a surface film rather than a penetrating finish. Early morning application (when the sun is still low) works well for south and west-facing decks.

Back-brushing technique: This is the key professional technique most DIYers skip. Apply stain with a paint pad or roller, then immediately work it in with a brush, brushing with the grain. This works the stain into the wood fibres and evens out the application. Without back-brushing, roller application leaves too much stain on the surface rather than in the wood.

Don't over-apply: More stain is not better. Most penetrating stains need only one coat on raw or freshly cleaned wood. Two-coat applications are appropriate only when the first coat has fully absorbed (dried) and the wood still looks thirsty. Excess stain sitting on the surface becomes tacky and peels.

Work in sections: Complete one full board at a time, end to end. Starting a new board in the middle creates lap marks that are visible in the dried finish.

Don't forget the end grain: Cut ends of boards absorb stain very quickly and often need an extra pass. End grain that isn't properly sealed is the primary entry point for moisture that causes rot.

Annual Maintenance: Protecting Your Investment

A properly cleaned and stained deck doesn't need full stripping and restaining every year. With semi-transparent penetrating stain, a light annual maintenance wash in spring and a spot recoat where the finish shows wear will extend the life of your staining job significantly.

Annual spring maintenance:

1. Sweep and rinse the deck thoroughly
2. Apply an oxygen bleach cleaner to remove winter mould and mildew
3. Light rinse (no heavy pressure needed — just a garden hose)
4. Allow to dry, then inspect for areas where the stain has worn through
5. Spot recoat worn areas with a brush

Re-drive or replace any fasteners that have worked loose over the winter. Check the ledger board connection to the house annually for rot or loose hardware — this is the most structurally critical part of your deck.

When your deck's stain reaches the end of its lifespan (usually 2–4 years for semi-transparent), the process repeats: clean, brighten, dry, and restain. If you've been using a penetrating stain and maintaining it properly, you should not need to strip or sand the old finish — just clean and apply a fresh coat.

Our deck pressure washing service handles the cleaning and prep work, leaving you ready to stain the following day (or the week after, once it's properly dried).

D&D Home Services TeamExterior Cleaning Experts

D&D Home Services is Kitchener-Waterloo's trusted exterior cleaning company serving Kitchener, Waterloo, Cambridge, and Guelph.