How Soon Should You Put Waterproofing on After Power Washing Treated Wood?

Cleaning

• Clean off any debris from the top of the pressure-treated wood and remove any material that is stuck in the gaps between the wood. Leaves, twigs and other debris retain moisture, which can prematurely deteriorate the wood. You can use some household cleaners or bleach to clean your deck, but according to Decks-R-Us, it is better to apply a deck or treated wood cleaning solution from your local hardware store. If you do not wash off the household cleaners or bleach quickly enough, they can damage or discolor the treated wood.

Power Washing

• No waterproofing will last long if you apply it to dirty wood. Whether you are power washing new, pressure-treated wood or older wood, this is the best way to clean the surface before applying waterproof sealant. Engage the trigger of the power washer at an angle, directing the water away from you. Instead of using a sweeping motion, start power washing at one end of the deck, traveling from one end to the other without stopping. Make sure your second pass overlaps the first pass. If you do need to stop in the middle of a pass, move the tip of the power washer up and away from the deck before releasing the trigger.

Time Frame

• Many waterproofing sealants can be applied to damp or moist wood. Thompson's states its waterproof sealants can be applied to freshly cleaned, treated wood that is damp. The pressure washer has opened the pores of the wood, so the sealant will penetrate the treated wood better, and the coating will seal the wood properly. Apply the waterproofing the same way that you power washed the treated wood. Make even strokes in one direction, instead of a sweeping motion. Let the waterproofing dry completely before applying another coat.

Problems and Precautions

• Do not apply waterproof sealant if the local weather service expects rain within 24 hours after applying the sealant. Check the local forecast before scheduling a time to clean and waterproof your pressure-treated wood. Also, do not apply the sealant during the hottest part of the day. The sun will heat the pressure-treated wood, and the waterproofing will not stick to the surface properly. If water stands in one spot of your deck for more than 24 hours, you must make repairs to that section to ensure the water runs off of the surface.