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A Guide to Power Washing a Wood Deck
Guys seem to love equipment that makes noise, is powerful and saves time. A chemical deck brightener may not do the job of deep cleaning but a power washer can fit that bill just fine. But it can also ruin your wood deck!
Why? Because most people don't use the power washer properly and use it with too high a jet pressure (that's the "power" part) and place the tip too close to the soft wood.
A power washer can be powerful enough to etch brick or gentle enough to wash siding. They... come in various sizes, some providing over 4,000 psi (pounds per square inch) of water pressure some only a few hundred, some are run by gas engines, some by small electric motors, they have a variety of pressure wand tips and can handle many different tasks.
Using a power washer to deep clean a wood deck can be done successfully but there a lot of horror stories about a power washer becoming a power etcher when improperly used on wood. The result of improper power washing? Well, it can require wood replacement or cause a ruined deck at its worst and require serious sanding at best.
In this tutorial we will review the few key points to successful power washer use on a wood deck in the process of refinishing a wood deck:
Continue to 2 of 4 below.
- Pressure Selection
- Tip Selection
- Power Washing Technique
- Post-Washing Sanding
02 of 04
Power Washing: Pressure and Tip Selection
Because the power washer is so versatile and can be used for so many different tasks, they come in many pressure ratings and tip styles depending on their intended application.
We recommend the following pressure and tip selections for cleaning wood:
Continue to 3 of 4 below.
- Use as low a pressure as possible while still being effective;
- Pressure for soft wood like cedar or pine should be at about 500 psi to 600 psi, harder woods may go higher but no more that 1200-1500 psi;
- Use a fan tip (preferable) or carefully use a... rotating tip (shown here);
- Always start the water pressure by depressing the trigger away from people and glass windows and at least 24" away from the wood deck, then feathering it into range of about 12-18" from the deck;
- As a rule of thumb, try to never get closer than 12" from the wood deck unless you're at low pressure.
- Test your pressure and its effectiveness in as inconspicuous an area as possible. Maybe a stair tread. If you mess up and have to replace a piece of wood because you etched it, a stair tread is easier to replace than a deck board.
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Power Washing Technique
Here are some tips for proper power washing technique.
Continue to 4 of 4 below.
- As mentioned previously, you will most usually use a fan tip on the power washer. Fan tip size is measured in degrees, with a 40 to 60-degree tip size being the norm for deck cleaning.
- Set your pressure to 600 psi to see if that will work for you. Increase the pressure incrementally as needed to clean the deck but not damage or etch the wood surface.
- Engage the trigger a couple of feet away from the deck surface and then lower the wand to about... 12" off the surface and clean the deck using a sweeping motion.
- As you sweep you will have a tendency to pivot with your arm but that will create an inconsistent distance of the tip from the deck surface. Try to keep a consistent distance as you sweep. You can do this by moving your arm laterally back and forth.
- Work from the house outward.
- Work with the grain by feathering your spraying lengthwise with the deck boards and overlapping each area slightly. The key is you want an even cleaning with no hot spots or visible "cleaning edges."
04 of 04
Raised Wood Fibers
The key with power washing a wood deck is to not ruin the wood and etch or erode the soft wood fibers. However, wood is wood and when wood gets wet, it raises the fibers creating a rough surface. This is especially a problem on handrails where the raised fibers = splinters.
You have a couple choices. One, if you did a great job with minimal damage and you just wanted to clean the deck, then you may be able to get away with a spot sanding here and there. Two, if you are going to refinish... (re-stain or reseal) the deck, you need to sand the wood deck.
It is not that hard and will result in smooth boards, little to no splintering, open wood pores so the wood soaks up the sealer/stain, and all kinds of good stuff.
When sanding, do not use too fine a grit sandpaper or the stain/sealer will not soak in easily. Follow these guidelines: