Is It OK to Pressure Wash a Deck?

Wood decks are easily gouged by too much pressure.

The best trained professional boxer or martial artist can generally apply between 400 and 800 lbs. per square inch of pressure with a punch, with the average person averaging about half that. With that bone-crunching number in mind, imagine what 3,000 psi can do. That's the danger you risk when using a pressure washer, and if you decide to use it on your deck, you must take proper precautions.

Proper PSI

Most pressure washers can reach power levels around 3,000 psi, with some reaching even higher. More is not necessarily better when it comes to pressure washing your deck, and you must carefully adjust the pressure to ensure a good clean without damaging the wood. Never use more than 1,500 psi on a wood deck. This is a powerful blast of water that will wash away dirt, dust, mud and debris, but is not strong enough to gouge even softer woods.

Cleaning Solution

Most pressure washers are used only for spraying water, so you will likely use the washer to rinse away a cleaning solution. Apply your deck cleaner with a spray bottle or scrub brush. Make sure the deck is slightly damp before you start; you can use a regular hose for that part. Then spread the cleaning solution around with a scrub brush, push broom or a garden sprayer. If your solution is not chemical-free, make sure you cover up surrounding plants so that they are not harmed by the solution.

Running the Washer

Use a 40- to 60-degree fan tip to avoid spraying the water too directly against the deck surface. Hold the tip at least 12 inches from the deck surface when you begin, until you get a feel for the pressure and how it works. If necessary for tough dirt and grime, you can hold the tip 6 inches from the surface, but any closer will cause serious damage. Sweep the nozzle across the deck from side to side, keeping the distance and pressure even so that you don't have different colors in different areas. Overlap sweeping passes by 2 to 3 inches to hide seams, and always work with the grain of the wood for best results.

Safety

Never start the washer and pull the trigger with the nozzle pointed at anything living or breakable, especially people, animals and glass. You will get wet as you run a pressure washer, so wear waterproof shoes and old clothing. Don safety goggles to protect you from shrapnel and water that will bounce off of the surface as you work. Never exceed the recommended psi, unless directed by a professional.

References

• Decks: Using a Pressure Washer to Clean a Deck
• YouTube: Pressure Wash Your Deck Like a Professional
• "Connect Savannah"; The True Force of a Boxer's Punch; Cecil Adams; July 2010