How to Pressure Wash a Cedar Deck

Clean your deck every fall to maintain it.

Naturally rot-resistant cedar is often used for decks and other outdoor applications because of its durability. But like all woods, it eventually shows signs of weathering and decay if not properly cared for. Rain, dirt and the grease from your grill all leave their toll. Clean and seal your deck in the fall, after barbecue season is over, but before heavy snows arrive. Reseal the deck every two to four years, depending on use and your environment.

Things You'll Need

• Trisodium phosphate
• Bucket
• Large sidewalk brush
• Chlorine bleach
• Sealant
• Paint rollers

Instructions

1. Mix 1/2 cup trisodium phosphate and 1 gallon hot water in a bucket. Dump the cleaning solution directly on the deck. Scrub the deck with a large sidewalk brush to remove grease and stains. Rinse with a garden hose.

2. Mix 1 qt. chlorine bleach with 1 gallon hot water in the bucket and pour it on the deck. Spread the solution over the entire surface with the sidewalk brush. Wait 30 minutes and rinse. The bleach destroys mildew and brightens the color of the wood.

3. Attach a garden hose to the pressure washer and hook up the pressure washer hose as well. Attach a 40-degree fan nozzle to the pressure washer hose. Set the pressure at 3,000 PSI. Turn on the water and start the machine.

4. Pull the nozzle to force a stream of water onto the deck. Use long, steady continuous strokes and point the water at a low angle to the deck, rather than directly at the surface.

5. Allow the deck to dry for 48 hours. Apply a water-repellent deck sealer with a paintbrush or paint rollers.

Tips & Warnings

• Inspect the deck for signs of decay and replace any rotting boards and rusting screws before pressure washing it.

• You may be able to put cleaners and bleach directly in the pressure washer to further simplify the task. Read the owner's manual, though, to avoid damaging the pump. When in doubt, use a cleaner specifically made for pressure washers.

• Oxalic acid is a stronger bleach that is safe for use on cedar decks. It is highly corrosive, so read and follow all directions carefully.

• Wear garden boots and waterproof pants to protect your feet and legs from injury.

• Never aim the pressure washer at glass or other people because the powerful stream of water can cause damage or injury. Cover plants and unprotected surfaces with plastic sheeting.

• Pressure washers can gouge the wood, causing permanent damage. Use a light touch and always angle the flow of water.

References

• This Old House: Refresh Your Deck
• Western Red Cedar Export Association: Refinishing Western Red Cedar Decks
• Iowa State University Extension: Fall Deck Care

Resources

• This Old House: Deck Defense