A Full Guide to Power Washing the Deck
Updated: May 17, 2024
Deck seen too many summers? Give it a new lease on life. Learn how to power wash your deck to remove old coatings.
Time 4 to 6 hours
ComplexityBeginner
Cost$250 to $300
Introduction
If you've been putting off power washing your deck because you think it requires a lot of time, tools and know-how, take heart. With the help of a pressure washer and special products that help remove dirt, mildew and old finishes, prepping a deck for new stain is a DIY-friendly project. "It's all about using the right equipment and chemicals," Ryan Ghent from Element Pressure Washing says. Whenever I pressure wash a deck, I let the cleaning and stripping agents do the heavy lifting and use the pressure washer to thoroughly wash it clean.
The process outlined here will work on any wood deck previously coated with oil stain, including redwood, cedar and pressure treated lumber. Power washing a deck does not require any special skills, and you'll save several hundred dollars by doing the work yourself. Ahead, you'll find a comprehensive step-by-step guide and expert tips for effectively pressure washing a deck to prepare it for a fresh coat of stain.
Pros and Cons of Power Washing Your Deck
Pros: Power washing your deck is a fast and thorough way to remove grime, dirt and previous coatings with little physical effort. Plus, pressure washers are available and user-friendly.
Cons: The strength of a pressure washer can damage a wood deck if not used properly. Wood can be damaged or scarred by a pressure washer on a high pressure setting. Power washing also drives water deep into deck boards, so you'll need to wait several days for the deck to dry thoroughly before staining.
When to Call a Pro
This is a beginner-level project, but if you don't have the time or desire to prep your deck, call a professional. Ghent suggests hiring out the prep, then stain the deck yourself.
How Much Does Hiring a Pro cost?
Expect to pay 75 cents to $1.25 per square foot to have your deck professionally power washed for re-staining. For a 500 sq. ft. deck, that would come to $375 to $625 to remove old coatings.
This process uses more chemicals and takes longer than a simple deck cleaning, which would cost 25 to 50 centes per square foot. "It depends on the overall condition of the deck and the degree to which treatment is required," Ghent says.
For smaller decks, there may also be a minimum service fee charged.
Before You Begin
Pressure Washer Notes
Rent a pressure washer from a home center or rental center. Rent a unit that allows for the intake of chemical cleaners (deck stripper and wood brightener) so you can spray them on through the wand. Most pressure washers have an intake hose that draws in cleaners from a separate bucket. (Use a plastic bucket. Chemicals in the cleaners can react to metal buckets.)
Tips for using a pressure washer:
- A pressure setting of 1,000 to 1,200 psi is ideal for pressure treated wood. For soft woods like cedar, use a lighter pressure setting, between 500 and 600.
- Keep the wand at least 8 inches away from the wood surface at all times to avoid surface damage.
- Keep the wand moving, so you don't gouge the wood and avoid sudden stops. "Use long sweeping motions with a quick flicking at the end to pull it away from the surface," Ghent says, "or you'll end up with a lot of start and stop marks."
- Go over stubborn mildew or other stains a few times rather than turning up the pressure or trying to heavily scour the wood.
Material Notes
We used sodium hydroxide to strip the deck. You can find a deck stripping product with sodium hydroxide as the active ingredient in almost any home center or paint store. Read the label on the container to find out what's suggested for your stripper.
Sodium hydroxide works great to remove oil stain. If your deck has a water-based coating, you may want a stronger stripping product that is applied with a paint roller and brush.
We also used oxalyc acid as a brightener after stripping. This product is available at home centers and paint stores. It works fast, won't harm the wood and is environmentally safe in the diluted solution that you'll use. "Brighteners lighten the wood and get it looking really clean and natural," Ghent says, and balance the wood's natural PH.
Like strippers, some deck brighteners come premixed and some need to be diluted with water. Read the label for the manufacturer's recommendations. We mixed our oxalic acid with an equal amount of water and ran it through the pressure washer's intake hose.
Tools Required
- broom
- Chemical resistant gloves
- Deck scrub brush
- Drop cloths
- Eye protection
- Garden hose
- Orbital sander
- Plastic bucket
- Pressure washer
- Putty knife
Materials Required
- Deck stripper
- Latex gloves
- Oxalyc Acid
Project step-by-step (9)
Safety precautions
To use the pressure washer:
- Wear appropriate safety gear and clothes. Rubber boots and gloves will protect your hands and feet. Safety goggles will keep the chemicals from splashing into your eyes, and a disposable respirator or dust mask will filter fumes.
- Keep the exhaust from the pressure washer at least 3 ft. away from any objects, including your house.
- Practice spraying the water until you find an appropriate power setting.
- Never point the wand at anything you don’t want to spray.
- Cover electrical outlets.
To use chemical strippers and brighteners:
- Wear appropriate safety gear and clothes. Eye protection and chemical-resistant gloves are advised.
- Follow all manufacturer’s instructions for mixing ratios and handling.
- Keep chemicals away from eyes and skin.
- Read product instructions carefully and follow all safety protocols.
Prep the area
Although most strippers aren’t supposed to harm vegetation, it’s still a good idea to protect plants and it only takes a few minutes.
- Heavily douse the plants or grass under and around your deck with water and cover them with plastic. Once you’ve finished cleaning the deck, immediately remove the plastic.
- Spray down the siding with clean water to ensure that any stripper that splashes onto the house will easily wash off.
- Before you begin power washing your deck, make any needed repairs, such as replacing cracked or split boards and broken balusters.
Apply stripper to the deck
Use the pressure washer to apply the stripper to the deck railings and then the deck boards.
- Attach a wide orifice soap/chemical nozzle to the pressure washer wand.
- Pour stripper into a plastic bucket.
- Place the pressure washer intake hose into the bucket.
- With the pressure washer, apply stripper to the top rails and down the balusters.
- Next, apply stripper to one deck board at a time, using a gentle sweeping motion.
- Work from the end of the deck toward the exit.
- Let the stripper sit or ‘dwell’ on the deck for the manufacturer’s recommended time.
Remove the stripper
After waiting the recommended dwell time, use the pressure washer to wash off the stripper and old coatings.
- Attach a 25- or 30-degree tip in the wand of the pressure washer and set the pressure washer to a psi of 1,000 to 1,200.
- Keeping the tip of the pressure washer wand 8 to 10 in. from the wood, work from the top down.
- Spray balusters at the corners to scour two sides at once.
- Pressure wash along the length of the boards.
- Rinse the siding and windows with clean water at low pressure to remove chemical residue.
- Repeat these steps on any areas with remaining stain until all previous coatings have been removed.
Clean out the gaps between decking
If there’s still debris trapped between deck boards, such as leaves or twigs, remove it now.
- Dig out trapped debris from between deck boards with a putty knife. “Sweep or vacuum any dust or debris,” Pancione says.
Brighten the wood
Oxalyc acid will brighten the wood in a matter of minutes and make it more receptive to the stain. Apply and rinse wood brightener with the pressure washer.
- On a low-pressure setting, soak the deck with clean water.
- Attach a wide orifice tip to the pressure washer wand.
- Pour the brightener into a plastic bucket.
- Place the pressure washer intake hose in the bucket of stripper.
- Use the pressure washer to apply brightener to the top rails, balusters and deck floor.
- Use a long-handled scrub brush to clean the wood. “Scrub in the direction of the wood grain,” Pancione says.
- After waiting the manufacturer’s dwell time, rinse the railings, balusters and deck floor with water to remove any brightener residue. “Use a lower pressure with a wider fan on the pressure washer,” Pancione says. Around 500 psi is all that is needed.
- Finally, rinse off your siding with a garden hose to remove any brightener that may have splashed onto it during this process.
Pro tip: Brightener is activated when it is wet. If it begins to dry during the dwell time, reapply some to the dry spots.
Let it dry
Allow ample dry time before applying paint or stain. “Moisture in the wood can cause the new coating to fail, or can create bacterial growth underneath the stain,” Ghent says.
Both pros recommend several days of drying time (with no rain) before applying any stains to the surface.
Sand if necessary
Chemicals and pressure washing may lift wood fibers and require sanding before stain can be applied.
“If sanding is necessary, it can be done with either palm sanders for smaller decks or you can rent a larger sander from a home center, working in the direction of the wood grain,” Pancione says.
FAQs
Can you power wash composite decking?
You shouldn’t if it can be avoided. Composite decks can be softer than wood and can be permanently damaged from a high pressure power wash. Also, chemical strippers and brighteners should never be used on composite decks.
How long should you wait to stain a deck after pressure washing?
“Three days minimum with no rain,” Ghent says. “If you get rain or a high moisture day, restart the clock.” You want to make sure the wood is completely dry before staining.
How often should you power wash your deck?
Whenever you are preparing to reapply stain, which will vary depending on the condition of the wood, sun exposure and type of stain. If applying proper pressure and chemicals to your deck, power washing will not cause any harm.
About the Experts
- Shayne Pancione is the owner of Pancione Painting Plus, a full-service residential and commercial painting company in Easthampton, Massachusetts. He has over 25 years of experience in the trade.
- Ryan Ghent is the owner of Element Pressure Washing, a residential pressure washing company in South Deerfield, Massachusetts. He has four years of industry experience, including many decks.
Originally Published: July 12, 2021
