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How to Power Wash Your Deck

25 April 2023

Monnick Supply

The FYI on power washing your deck to perfection

What you'll need:

  • Power washer
  • Deck brush
  • Mild detergent
  • Safety goggles
  • Work gloves
  • Waterproof boots
  • SUPPLIES Waterproof tarps
  • Chemical brightener (optional)
  • Sandpaper (optional)
  • Wood stain or sealant (optional)

Let’s face it: Decks can accumulate layers of dirt and grime, but power washing your deck can transform it quickly. If you’re ready to restore your deck to its former clean glory and prepare it for spring and summer cocktails, follow our guide and learn how to power wash your deck, removing signs of previous seasons.

Prepping to Power Wash Your Deck

Power washing is serious business. Spraying water at high pressure can damage you, your home, or items around your home, so you must wear protective gear while completing this project. Don goggles, heavy boots, and work gloves. Wear pants, not shorts. You should also cover any shrubs, trees, or plants around your deck, and remove potted plants so they don’t get caught in the line of fire. Don’t forget to place a tarp over electrical components and light fixtures, and close all windows and doors.

You’ll also want to choose the right pressure washer for your deck. You should use one that emits the lowest pressure possible while cleaning your deck thoroughly. If you have a soft wood deck (cedar or pine), 500 to 600 psi should work. Pressure-treated wood can handle 1,200 to 1,500 psi.

Pre-Treat the Surface

Using a mixture of water and mild detergent and armed with a deck brush, try to remove the first layer of gunk without any machinery. If you have a composite deck, as opposed to one made from wood, you shouldn’t need to do anything more than this step—power washing is more powerful cleaning than composite decks require. Spend a little extra time scrubbing those nooks and crannies around corners.

Test the Machine

As we noted, a power washer is a powerful tool, so test out the machine before diving in. Connect the hose to the machine and turn the machine on, ensuring that nothing is obstructing the hose between the machine and your deck.

Set the machine to the lowest pressure, and select a spot on your deck to test it—ideally a back corner or somewhere largely out-of-sight. Adjust the angle of the spray and your distance from the wood to ensure you are cleaning the deck without causing any damage. You’ll likely want to stand 12 to 18 inches away. As you’re working, keep the water away from your home’s structure, as it could lead to mold growth.

Power Wash With Care

If your test went well, it’s time to start power washing the wood deck. You’ll want to spray the water in the same direction as the wood grain, using sweeping motions, and should start with the deck boards closest to the house, moving outward as you go.

Don’t spray in a zig-zag or diagonal pattern, which could score the wood. You can go over the area twice, but maintain even motions throughout the process.

Apply a Chemical Brightener

If your wood is stained, you could apply a chemical brightener to make it shine. Pick a product intended for deck wood and power washers, and check that your machine is compatible with chemical cleaners. Keep in mind that this step is optional, and you shouldn’t attempt it on composite decking.

Mix the solution as required in the manufacturer’s instructions, then apply the chemical to the wood. Complete a last wash with water. As these brighteners re-texturize the wood, you’ll want to sand it before applying a deck stain or sealant.

Allow the Deck to Dry

Whether or not you choose to apply a deck stain or wood sealer, allow your deck to completely dry before you use it again. You should ideally allow the deck to dry overnight. If you wish to stain or seal the deck, you should sand the surface using 60- to 80-grit sandpaper first. This step will flatten any raised wood fibers, which can cause splinters.

Need to rent a power washer? Contact Monnick Supply.



Marlborough Store

135 Maple Street,
Marlborough, MA
Call (508) 318-4788


Mon-Sat 7:00am to 5:00pm

Framingham Store

759 Waverly Street,
Framingham, MA
Call (508) 386-9876


Mon-Sat 7:00am to 5:00pm

Monnick Supply $$
135 Maple St.
Marlborough MA 01752
United States
(508) 318-4788
Mon-Fri 7am - 6pm
Sat 7am - 5:30pm
Sun 12pm - 4pm
Monnick Supply $$
759 Waverly St.
Framingham MA 01702
United States
(508) 386-9876
Mon-Fri 7am - 6pm
Sat 8am - 5:30pm
Sun 10am - 4pm