How to Clean a Wood Deck: Best Cleaner, PSI and Safe Mixing

The best way to clean a wood deck is to sweep it, wet it, scrub on an oxygen-bleach wash with the grain, and rinse thoroughly. Skip chlorine bleach on treated lumber, and never mix one cleaner with another. A pressure washer is optional, and the makers disagree on settings. This guide covers cleaner choice, safe mixing, the wash steps, real pressure-washer numbers, and drying.

Which Deck Cleaner Should You Use?

The right cleaner depends on what is on the boards. Oxygen bleach (sodium percarbonate or hydrogen peroxide) is the safe default for green or black growth, chlorine bleach is the one to avoid on treated wood, and an acid brightener is a separate finishing step, not a substitute for washing. The table compares them using what the Treated Wood information site, Simple Green and DEFY publish for their own products.

Cleaner	Best use	What the sources say	Watch out
Mild dish detergent + warm water	Light dirt, pollen, routine upkeep	Treated Wood: dilute mild dish detergent in a bucket and work a stiff brush over a small area at a time	Will not kill mildew roots
Oxygen bleach (sodium percarbonate)	Mildew, algae, green or black growth	Treated Wood: more effective on deeper-rooted growth in porous wood; hydrogen peroxide kills mildew on contact within minutes. Simple Green Oxy Solve: 1 part to 20 parts water, 3 to 5 minutes dwell on its product page, 5 to 10 minutes on its deck guide	Never let it dry on the wood; mix only to the label
Chlorine bleach cleaners	Mildew on a deck that has no other option	Treated Wood: excessive use can damage treated wood and leave an unnatural whitewashed look. Cabot: bleach-based mildewcides must stay wet for at least 10 to 15 minutes to work	Never mix with ammonia, acids or any other cleaner
Oxalic-acid brightener	Restoring color and pH after a cleaner	Treated Wood: used after cleaning to restore natural pH. DEFY Wood Brightener: 1 part to 4 parts water, 3 to 5 minutes, goggles and rubber gloves, causes severe skin burns and eye damage	A finishing step after a thorough rinse, not a first wash

Safety First: Never Mix Deck Cleaners

The CDC’s bleach guidance is blunt: never mix bleach with ammonia or any other cleaner. On a deck that rules out the common homemade tricks, such as adding ammonia-based glass cleaner for extra power or splashing a second cleaner onto a spot you just treated with a chlorine product. Simple Green’s own label for Oxy Solve likewise says not to mix it with bleach or any other chemicals.

That has one practical consequence for the brightener step. If you used a chlorine mildewcide, rinse the boards completely and let the deck drain before any acid brightener goes on, so the two never meet on the wood. Following the same logic, use one cleaner per pass.

• Protect yourself: the CDC lists rubber or other non-porous boots, gloves and eye protection for bleach work, and Cabot adds old clothes and warns that deck boards may be slippery.
• Protect plants: Treated Wood suggests covering shrubs with a plastic drop cloth and spraying nearby plants with water to dilute overspray, and DEFY and Simple Green both say to rinse plants the cleaner touches.
• Store it safely: keep mixed solution in a labeled bucket, not an old drink bottle, and keep it away from children and pets until the deck is rinsed.

Mildew, Algae or Just Dirt?

Dark specks that sit in the grain are usually mildew, a slick green film after wet weather is usually algae, and silvery boards with no growth are just weathering. Cabot lists mildew and algae together as growths that a bleach-based cleaner has to stay wet on for 10 to 15 minutes to destroy, and an oxygen-bleach wash handles both on most decks. If the boards are gray rather than dirty, cleaning will not bring the color back; see our guide to removing gray weathering from wood.

If you would rather follow a single product walkthrough, our OxiClean deck cleaning guide covers that one cleaner in detail, and for dense tropical hardwood see how to clean an Ipe deck.

How to Clean a Wood Deck Step by Step

1. Clear and sweep. Remove furniture, planters and grills, then sweep with a stiff broom, including the gaps between boards, so loose debris does not turn to mud.
2. Check the boards. Sink popped nails and tighten loose screws now. If a board is rotted through, replace it first; our guide to pressure-treated lumber sizes and ratings helps you match the replacement.
3. Protect the surroundings. Cover shrubs and wet nearby plants with plain water first, and close windows and doors if you will use a sprayer.
4. Wet the deck. Rinse the section with plain water so the cleaner works on the surface instead of soaking in unevenly.
5. Apply the cleaner by section. Mix to the label, apply with a pump sprayer or brush, and work only as much deck as you can rinse before the cleaner dries. The makers’ dwell times run from 3 to 15 minutes, so follow the one on your bottle.
6. Scrub with the grain. Use a stiff synthetic brush on dirty areas; scrubbing across the grain roughs up the surface.
7. Rinse thoroughly. Rinse from the high side toward the low side, flushing the gaps between boards and any plants the cleaner touched.
8. Brighten if needed. On a gray or tannin-stained deck, follow with an acid brightener at its label dilution, then rinse again.
9. Let it dry. Do the water-drop test described below before you apply any stain or sealer.

The video below shows the full wash, renew and seal sequence on a real deck if you want to see the motion of scrubbing and rinsing before you start.

Pressure Washer Settings: What the Makers Actually Say

A pressure washer is faster than a brush but it is also the quickest way to gouge a softwood deck. Here is the surprise: the published guidance does not agree. The table lists what each source I read actually states, and where a source gives no number, it says so.

Source	Pressure	Tip	Distance from wood
Sherwin-Williams deck prep guide	1200 to 1400 psi	45-degree tip, spray with the grain	8 to 12 inches
Cabot Technical Bulletin 12 (2008 update)	2000 psi called adequate for general cleaning (citing a 1990 magazine article)	40-degree tip; rarely a 0-degree tip for homeowners	At least 8 to 10 inches (stated for siding)
Treated Wood information site	No number given	Fan tip only, 40 to 60 degrees; never a narrow or rotating tip	Start at least 24 inches away; avoid closer than 16 to 20 inches at anything but very low pressure
Karcher deck guide	No number given	Flat spray nozzle; avoid dirt cutters	About 30 cm (roughly 12 inches) when rinsing
Simple Green Oxy Solve label	High-pressure rinse after dwell	Spray perpendicular to the surface	At least 2 feet

The practical rule: no source I read gives separate psi numbers for cedar, pressure-treated pine or hardwood, so do not trust any chart that does without citing a maker. The shared advice is a fan tip, a wide stance, and the lowest pressure that lifts the dirt. Start at the farthest distance in the table, test a hidden board, and step closer only if nothing lifts. Stop the moment the surface fuzzes or the wood fibers lift.

Cabot also notes that deck boards get slippery, and that you should practice on a surface that cannot be damaged first. If the boards feel fuzzy once dry, sand lightly with the grain; our sandpaper grit chart shows which grit to use for that kind of light surface prep.

How Long to Wait Before Staining or Sealing

There is no universal drying time. Treated Wood says to sprinkle a few drops of water on the deck and test whether the wood readily absorbs them, then stain a small area to confirm the boards are ready. Sherwin-Williams requires the deck to be completely dry before sanding. A shaded deck in humid weather can take far longer than a sunny one, so judge by the water test, not the calendar.

Once the wood passes the test, pick the finish for your wood: our guides cover sealing a pressure-treated deck and how to restain a deck. If you are painting rather than staining, the water test in our guide on painting pressure-treated wood works the same way. For the wider picture of keeping outdoor wood in shape, see the wood care and maintenance guide.

Deck Cleanup Checklist: Spring and Fall

A proper deck cleanup twice a year keeps your wood deck looking its best and extends its lifespan. Here is a quick deck cleanup checklist to follow each season:

Spring Deck Cleanup

• Clear debris: Sweep off leaves, dirt, and winter grit with a stiff-bristle broom.
• Check for damage: Inspect boards for cracks, splinters, popped nails, or rot after the freeze-thaw cycle.
• Wash the deck: Apply an oxygen-bleach deck cleaner mixed to its label and scrub with a deck brush. Rinse thoroughly.
• Let dry completely: Use the water-drop test before applying any sealant or stain.
• Reseal if needed: Apply a water-repellent sealant if the wood is absorbing water instead of beading it.

Fall Deck Cleanup

• Remove outdoor furniture: Store or cover chairs, tables, and planters before the wet season.
• Clear fallen leaves promptly: Wet leaves trap moisture and accelerate rot, so don’t let them sit.
• Quick wash: A light rinse with a garden hose and mild soap removes summer grime and prevents mold buildup over winter.
• Inspect fasteners: Tighten or replace any loose screws and nails before winter.

Keep reading

• DIY Wood Deck Cleaner: Dish Soap, Water and a Scrub Brush
• How to Clean a Wooden Deck (Oxygen Bleach Method)
• How to Remove Rust Stains From Composite Decking (Safe PSI Guide)

Frequently Asked Questions About Cleaning Wood Decks

How often should I clean my wood deck?

Clean most wood decks once a year, with spring a common choice. A shaded, damp or heavily used deck can need a second wash in fall, and spot-cleaning spills as they happen keeps stains from setting.

What is the best homemade cleaner for a wood deck?

For routine dirt, use a mild dish detergent diluted in a bucket of warm water with a stiff brush. For mildew, use an oxygen-bleach powder (sodium percarbonate) mixed exactly as its label says, because ratios vary by brand. Never add chlorine bleach, ammonia or any other cleaner to it.

Can I use a pressure washer to clean a wood deck?

Yes, with a fan tip of 40 to 60 degrees, the wand moving with the grain, and distance kept well back. Sherwin-Williams lists 1200 to 1400 psi with a 45-degree tip 8 to 12 inches away, while Treated Wood advises starting at least 24 inches out and using the lowest pressure that cleans.

Can I use chlorine bleach on a wood deck?

It is not recommended on treated lumber. The Treated Wood information site warns that excessive use of chlorine-bleach cleaners can leave treated wood with an unnatural whitewashed look. Oxygen bleach is the usual substitute, and chlorine bleach must never be mixed with ammonia or any other cleaner.

How long should a deck dry before staining?

No maker sets a fixed number of hours, because it depends on sun, humidity and the wood. Test instead: sprinkle a few drops of water on the boards, and when the wood readily absorbs them it is dry enough to take stain or sealer.