How often should you wash your deck?

Why bother

Grime and algae rot the boards and turn the deck into a slide. A thorough-tier job. Skippable when life's busy, worth it when it isn't.

Why it's a range

Once a year does most decks, ideally in spring. A shaded deck, or one under trees in a damp climate, grows algae faster and often wants twice, spring and fall. Sweep the debris off every week or two between washes and the muck never gets a foothold.

What the job involves

1. Clear the deck and sweep it off, then look it over for loose boards, popped nails, splinters, or soft spots, and fix those first. Don't wash rotting wood; the pressure only makes it worse.
2. Wet the boards and put on a biodegradable deck cleaner (a pump sprayer with wood cleaner cut half and half with water does the job), leave it about ten minutes, then scrub with a stiff brush.
3. Rinse clean, working with the grain. With a pressure washer keep it gentle: 500 to 600 PSI for softwoods like cedar and pine, up to 1,200 to 1,500 for harder woods, a wide 25-degree tip, and keep it moving so it doesn't gouge.
4. Let it dry right through, a couple of days. If the finish is due, that's the moment to restain or reseal, while the wood is clean and open to take it.

Do it yourself, or pay someone?

Yourself, for most decks. It's a half-day-to-weekend job needing a deck cleaner ($10 to $50) and a stiff brush, or a rented pressure washer ($40 to $120 a day from a home center) used with care. Call in a pro if the deck's large, well off the ground, or you're not easy with a pressure washer: deck washing runs about $150, typically $100 to $250, or roughly $0.30 to $0.70 a square foot, per Angi's and HomeGuide's 2026 cost guides.

What skipping it costs

$200 to $3,000 is what a neglected deck tends to cost once mold and damp set in, the kind of repair and refinishing bill Angi's 2026 figures put across that range. A deck left dirty traps moisture and grows mold, mildew, and algae, which slowly eats the wood while the surface turns slick. Leave it long enough and the rot reaches the boards, then the joists and the ledger, and the cheap wash becomes a full replacement: roughly $4,000 to $11,000 or more, and well past $15,000 if the damp gets into the home's framing. The wash itself is cheap. The cost is all in skipping it.

Signs it's overdue

• Green or black patches, slick algae, or a musty smell, worse on the shaded boards. Growth has taken hold and the deck is turning into a slip hazard.
• A grey, dull, or grimy surface where the dirt's built up and the old finish has worn. That's water sitting on bare wood instead of beading off it.
• Soft, spongy spots, or a flathead screwdriver that sinks more than a quarter inch into a board. The damp has already started, so that's a repair, not a wash.

When to start thinking about it

A few days' warning does it. Grumpty grumbles 5 days out, then leaves you alone. Mark it done and Grumpty sets the next one, every 12 months, so you can go back to forgetting it exists.

Questions people ask