How Much Pressure Is Needed To Clean A Deck

If you've neglected to clean your deck for years, there's a good chance that it's accumulated a lot of dirt, algae and fungus. Pressure washers, combined with some deck cleaner and a little hard work, can make your deck shine and look brand new.

The process of cleaning and pressure washing a deck can take a whole day, but the results are immediately noticeable. To make your deck shine, you'll want to budget around $150.

pressure washer cleaning a wooden white chair

Step 1: Rent a pressure washer

Some people own power washers, but most will need to rent one for this project. Hardware stores rent pressure washers for around $40 a day, and a deposit can run from $50-$100. Some stores allow you to schedule your rental online, and others require you to call the store.

Stores often offer either electric or gas-powered pressure washers. Here's what you need to know about the differences between the two:

Electric pressure washers:

Usually run lower PSI (pounds per square inch) than gas pressure washers, around 1000–2000 PSI.
Need to be plugged in, so you have to keep the cord from getting wet.
Can't be used with extension cords, or must be used with specific extension cords.
Work better for smaller, lighter jobs like cleaning patio furniture or soft wood.
Run quieter than gas pressure washers.

Gas pressure washers:

Run much higher PSI than electric pressure washers, around 2000–3000 PSI.
Require fuel to run the engine (meaning you have to buy fuel and prime the motor).
Work better for heavier jobs like hardwood, cement and stripping paint.
Run loud enough to make ear protection necessary.

If your deck is small with soft wood, an electric model will be your best bet; if you're working on a large area with hardwood, opt for a gas model.

Step 2: Take precautions

Pressure washers are exactly what they sound like, and they can break your skin if you use them wrong. Wear sturdy, thick clothing that fits; if a pressure washer catches the loose folds of your clothing, it can pull you into the stream.

Use eye protection as well; if a loose particle of anything flies off from your decking, safety glasses will save your eyes.

If you have pets or children, make sure they're well away from the area you're pressure washing.

Step 3: Reset your nails

To make your deck look brand new, check to see if your nails are protruding over the surface of the wood.

Since decks are outside, they absorb a lot of rainwater. When they get wet, the wood expands around the nails in the deck. And as the wood dries, it contracts around the nail. This process forces the nails upward, occasionally leading to nails popping up above the surface of the deck.

In addition to presenting an eyesore, these nails can hurt your feet and make it difficult to move patio furniture around. Start your deck cleaning off right by fixing this small problem.

To reset your nails, get a drift pin ($5–$20) from your local hardware store. These blunt metal cylinders allow you to hammer nails back into the wood without hitting the wood directly with the hammer, which can crack the wood. Take the drift pin and set it over the nail, then hit the pin with the hammer until the nail is flush with the wood.

Step 4: Clean the wood

Next, you'll want to clean the wood before you pressure wash the deck. This loosens up the dirt and algae that are making your deck look bad, which helps the pressure washer do its job effectively.

For a large job, it helps to have a pump sprayer. These large sprayers help you cover wider areas with a consistent application. They can run into the hundreds, but a cheap one, which should do the job fine for mot purposes, costs around $10 or $20. You'll need to purchase some deck cleaner, which costs around $20 for two gallons. Many deck cleaners are ready-to-use (meaning you won't need to mix them with water) and biodegradable.

Spray the entirety of the deck and let it soak for up to 15 minutes to allow the cleaner to penetrate the dirt and algae on the deck's surface. Then, use a long-handled deck-scrubbing brush ($10–$20) to push the dirt from the wood and off the deck. You can either rinse the deck down with a garden hose or, if you're ready to move on to the next step, start to pressure wash the deck.

man with pressure washer cleaning a wooden deck

Step 5: Pressure wash the deck

Be sure to test your pressure washer before you use it; a washer at high aPSI can damage your wood and chip away at your deck. If you can, test it on the underside of your deck, where damage and wear won't be visible. Read the instruction manual for your washer before you begin to work.

Your garden hose will provide the water that cycles through the power washer at high PSI, so hook up your garden hose to the power washer carefully.

Use the colored tips that come with most pressure washers, making sure to use the tip that creates the widest angle. If the tips are numbered, choose a tip that gives a 40–60 degree angle. A wide angle will ensure that a large amount of water doesn't concentrate on one area of your deck, potentially causing damage to the wood's grain.

Remember that you're dealing with a high amount of pressure; be prepared for a significant recoil once you pull the trigger. Don't stand on a ladder or a high surface while you use the pressure washer, as the recoil could force you off.

Keeping the trigger pulled, sweep the wand in a fan-like motion across the wood, being sure to not focus on one area for more than a second. If you find a spot with a lot of dirt, use multiple sweeps to clean it, instead of a contained burst. Keep the tip a foot or more away from the wood to avoid damaging it.

Bottom line

Once you've used the pressure washer to clean the deck, let it dry for 24 to 48 hours before you stain or seal it. Your deck's wood will return to a more natural color after it dries, thanks to the cleaner and the pressure washer.

Pressure wash your deck once every two or three years, and at most once a year. Washing it too often will contribute to erosion, whereas not doing it often enough will allow dirt and algae to build up.

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As part of the Consumer Affairs Research Team, Zack Reeves creates content that helps consumers make important decisions. He parses through fine details to present buyers with all the information they need to improve their lives.