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.
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