How to Power Wash Decks Properly

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By Granath Color Works
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Weathered deck before power washing

You can power wash a weathered deck to restore the original beauty. While great results can be achieved, power washing incorrectly can result in a streaky look and can even destroy your deck.

Difficulty: Moderate

Instructions

Things You'll Need:

Power washer (at least 1500 pds./sq.ft pressure rating)
Household bleach
Hose

Step 1

Typical power washer

Before the power washer comes out, prepare your work area. The power washer produces a dangerously strong stream of water that can be very damaging. Remove all plants and other decorative items from the deck and surrounding area. Cover any windows or doors that are in the work area with plywood. Then cover the surrounding foliage with heavy plastic. Be mindful of drainage as the power washer puts out a great deal of water. Heavy duty boots and eye protection are a must!(foul weather gear is very helpful if you have it!)
Step 2

Garden sprayer

If your power washer has a siphon option, connect the bleach container to it for the first step. If not, use a garden sprayer with a 25% bleach and 75% water solution. Either way, soak the entire deck with the solution. Use a wide fan tip and the lowest pressure setting if using the power washer for this step. Allow the bleach to soak in for 15 minutes.
Step 3

Disconnect the siphon and using pressure setting of between 1500 and 2500 psi and the tight fan tip, test the power washing effect on a hidden section of the deck. The wand should be held perpendicular to the surface at a distance of about 10 to 12 inches. Move the wand slowly across about a 6" section and stop. Inspect the area. You should see the original wood color and no "furring" (furry splintering of the surface). Lower the pressure and/or keep the tip a little further from the surface if you see "furring".
Step 4

Tight fan tip held PERPENDICULAR to the wood

Begin in the farthest corner and work your way towards the open end (usually stairs of some sort). Use slow, even sweeps with the power washer wand. Be sure to maintain an equal distance from the tip to the deck and MAINTAIN A PERPENDICULAR ANGLE to the work. If you don't keep the tip perpendicular, it will result in streaks as even pressure will not be maintained.

It is best to work your way along the total lengths of each board so you limit the overlaps of pressure spray.
Step 5

Once entire deck has been pressure washed, lower the pressure and go over the surface again. This time using a wide fan tip and the lowest pressure setting. All you are doing here is washing off any residual dirt and bleach that rises to the top of the wood after the high pressure pass.
Step 6

If any furring has occurred, it can be sanded off after the deck dries thoroughly.

Comments

Alishamitchum said

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on 8/13/2009 Great article, wonderful tips!

slphilbrick said

on 3/6/2009 I have to power wash my deck before staining about every 2 years due to it being on the south side. These are good tips and warnings on how to do it right !