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What PSI to pressure wash a wood deck
Updated
A wood deck needs less force than most people use. A home electric washer rated around 1,500 to 2,000 PSI is enough with a 25 degree tip (often green), held about a foot away and moved with the grain. Kärcher's deck guide gives about 30 cm, roughly 12 inches, for the rinse and says to always work in the direction of the grain.
Why decks get damaged
Wood is soft. A narrow tip or a turbo nozzle held close cuts into the soft rings between the harder ones. That leaves a fuzzy, raised grain and stripes that show every pass. Once it happens, the fix is sanding. The pressure number on the box is not the main cause. The tip and the distance are.
How to do it
- Sweep the deck and clear the gaps between boards.
- Wet the deck, then put down a deck cleaner made for pressure washers with the soap tip. Kärcher's guide says to leave its cleaner on for two to five minutes.
- Switch to the 25 degree tip. Start two feet away on a board near the edge, then move closer until the dirt lifts. Stop there.
- Work one or two boards at a time, end to end, in long even passes with the grain.
- Rinse the whole deck and let it dry fully before you stain or seal.
Nozzles to leave in the box
| Tip | On a wood deck |
|---|---|
| 0 degree | No. It can carve lines in wood |
| 15 degree | No. Generac lists it for hard surfaces like concrete and brick |
| 25 degree | Yes. Generac lists decks and wood as its jobs |
| 40 degree | Yes, for soft or old wood and final rinses |
| Turbo | No. It is a spinning narrow jet |
Which of our picks fit a deck
- Westinghouse ePX3500: rated 2000 PSI at 1.2 GPM, which is 2,400 cleaning units, with a 25 degree tip and a 25 ft hose. The catch is no 40 degree tip in the box.
- Sun Joe SPX3000: 2,436 cleaning units, both the 25 and 40 degree tips, and a 34 inch lance, which helps your back on a big deck. The catch is mixed owner reports on long term durability.
More cleaning units make a deck go faster, not safer. A mid range machine with the right tip is the better match than the most powerful one.
Check any listing's numbers with the cleaning units calculator, or see all five machines on our picks page.
Wet wood is slippery, and debris flies back at you. Wear eye protection and shoes with grip.