Should you pressure wash a wood deck before staining it?

Updated November 10, 2026 · KeystoneProGuide editorial team

Should a wood deck be pressure washed before it is stained?

It should be cleaned, but the U.S. Forest Service's Forest Products Laboratory advice is to let the cleaner do the work rather than the pressure. In a 2007 release, a supervisory research chemist at the laboratory said that before refinishing a deck you first must clean it. He also said that aggressive scrubbing or using a power sprayer can do damage to the surface that later makes it hard for an absorbing finish to work properly.

His method relies on a cleaning solution, time and a garden hose. The rest of this guide sets it out, with the cautions that came with it. The release is old, and the laboratory's fuller deck publications are PDFs that were not read for this guide, so treat the details as one expert's published advice rather than a standard.

What cleaner did the laboratory suggest?

The chemist suggested a commercial deck cleaner with sodium percarbonate as the active ingredient. As an alternative, he said a 4:1 solution of water and household bleach, with a little powdered laundry detergent added, may be used.

He was specific about the detergent. It should be powdered, he said, because liquid detergents, particularly those containing ammonia, can form noxious vapors when mixed with chlorine bleach. The U.S. Environmental Protection Agency (EPA) gives the same warning in its own words: never mix chlorine bleach with cleaners that contain ammonia, because toxic fumes could be produced.

Can a cleaner be too strong?

Yes. The chemist advised against an overly aggressive cleaner and said to start with a gentle mixture. Some cleaners, he said, are so strong that they will pulp the surface of the deck. Laundry bleach in particular tends to cause excessive pulping, removing the wood surface, and he said this is particularly true for cedar.

He gave a way to tell while you work: if a lot of loose fibers are washing away as you clean and rinse, the deck is probably being pulped.

How is the cleaner applied?

The steps in the release:

1. Spread the solution with a kitchen broom or sponge mop.
2. Let it sit for about 15 minutes, keeping the deck wet the whole time.
3. On a large deck, treat no more than 200 square feet at a time, since a bigger area is too hard to keep wet.
4. Rinse with large amounts of water from a garden hose for at least 10 minutes.

He said a cool, cloudy day is ideal, because it lets the deck stay wet and gives the cleaner time to work.

What about a power washer?

The release does not give a safe pressure for decks; its point is that the cleaner should do the work. The National Park Service, writing about historic features, makes a related point: some materials, including soft wood, can easily be damaged even at low pressures. Neither source addresses wood fences directly. If a company plans to use a pressure washer on your deck or fence, ask what pressure and which tip it will use, and ask to see a test on a board out of sight first.

How long should the deck dry before finishing?

At least one day in the sun, The chemist said, and two to three days are probably better. He said you can easily wait two to three weeks before applying a finish, and that warmer weather helps penetrating finishes work better. He liked to wait until April for the finish after cleaning in mid to late March. He was writing from Madison, Wisconsin, so adjust for local weather.

Which finish should follow?

The release describes three kinds of penetrating finish:

The chemist said that, in general, the more pigment a finish has, the longer it lasts and the harder it is to refinish. Clear finishes are the quickest to apply and easiest to redo. Semitransparent stains last longest but can leave lap marks; to avoid them he suggested finishing the full length of two to four boards at a time.

Is a painted deck different?

It can be. On a house built before 1978, the EPA requires anyone paid to disturb painted surfaces to be certified in lead-safe work. A painted deck, porch or railing on an older home falls under that rule if a company is paid to wash or strip it. If you are unsure what coating is on an older deck, ask before it is washed.

What does deck cleaning cost?

• Deck or patio wash. $100 to $200 (Angi and HomeAdvisor); HomeAdvisor gives $100 to $250 for power washing with hot water. HomeGuide gives $120 to $240.
• Wash, stain and seal. $0.50 to $1.50 a square foot (HomeGuide), with $65 more for each staircase.
• Fence. $150 to $300 (Angi and HomeAdvisor).

These are national figures; the cost guide has the full ranges. How often to wash covers timing, the warning signs guide covers when a deck is due, and businesses offering the service are on the pressure washing directory page.

Sources

1. Springtime Means Deck Maintenance for Many Homeowners, USDA Forest Service, Forest Products Laboratory (news release via Newswise)
2. Preservation Matters: Maintenance - Graffiti Removal from Historic Features, National Park Service
3. A Brief Guide to Mold, Moisture and Your Home, U.S. Environmental Protection Agency
4. Lead Renovation, Repair and Painting Program, U.S. Environmental Protection Agency
5. How Much Does It Cost to Pressure Wash a House? [2026 Data], Angi
6. How Much Does Pressure Washing Cost? [2025 Data], HomeAdvisor
7. Pressure Washing Prices, HomeGuide