Wood: Pressure Washing

When you think about tackling that labor-intensive job of repainting your home or
deck, and the hours of time needed to scrape and sand that loose, peeling paint or
stain, consider using a pressure-washing unit. The first step toward thorough surface preparation should include the use of this very effective tool. Careful use of a pressure washing unit may be the solution that will save you time and money when preparing your home for repainting.
It is estimated that 85-90% of your labor should go into surface preparation prior to staining/painting. Your labor can be substantially reduced with the proper pressure-washing equipment. Pressure washers can be rented for about $70-80 a day, which is inexpensive compared to the number of hours spent scraping and sanding. Unfortunately, the pressure washer isn’t always a cure-all. There are occasions when scraping and sanding may be necessary, such as areas where the pressure washer can not remove stubborn, cracked, multi-layered, brittle paint. By using the right pressure washer and technique, you will tackle most jobs with ease. The July/August 1990 issue of THE HOME HANDYMAN magazine featured an article on pressure washing. The article states that in order for a unit to produce satisfactory results, the pressure washer should be able to generate 1200 to 2500 pounds per square inch (psi) pressure at the tip, and have a flow rate of 3 to 4 gallons per minute (gpm) of water. Pressure washers generally come with at least four tip sizes expressed in degrees: 0, 15, 25, and 40. For general cleaning, a tip of 40 degrees and 2000 psi is adequate, however, for removing loose paint and stubborn dirt, a 15 or 25 degree tip may be necessary. A novice, or the average homeowner, will very rarely use a 0 degree tip. Used improperly, it can produce poor results and do damage to your wood.
Some pressure washers come equipped with an injector tank which can be filled with a strong chemical cleaner. As the water is pumped to the tip at the end of a hand-held wand, the cleaner solution is fed into the stream of water.
This method of cleaner application is acceptable, but the operator of the equipment must be knowledgeable about the dilution factors of the chemical being used. If the cleaner is reduced too much, it may not be effective in destroying mildew or algae growths. Bleach-containing mildewcides must remain on the siding or deck in a wet condition for at least 10-15 minutes to be effective. Using the pressure washer to apply the chemical cleaner can cause problems for the inexperienced handler. Cabot recommends applying Cabot Problem-Solver® Wood Cleaner from a garden-type pressure sprayer at the recommended dilution ratio found on the label. It is very important to read the instructions supplied by the pressure-washer manufacturer and the supplier of the chemical cleaner. When applying the cleaning solution, remember to wear eye protection and rubber gloves, and keep the cleaner out of the gloves to avoid skin irritation. Old clothing is a must. Scaffolding, ladders, and roofs can become slippery when contaminated with cleaning solutions, so be sure to exercise extreme
caution when working on these surfaces. When cleaning your home or a commercial building, please follow all safety rules for the best possible results. Below are a few pointers which should be considered:
• On siding, always wash from the bottom up and rinse from the top down. Otherwise, the cleaner will run down on the unwashed areas and leave streaks.
• Keep the nozzle or tip at least 8-10 inches away from the surface and perpendicular to the siding to avoid forcing water behind the siding. While holding the wand (tip) perpendicular to the siding, the tip may be tilted at a slight angle to the siding to allow the pressure stream to get under loose paint or stain and lift it off.
• Close all windows. Do not use the high pressure of the unit to rinse the windows. Glass damage may result. (To avoid streaking of window glass, Cabot recommends prewetting the glass with clear water and keeping it rinsed during the entire operation.)
• Do not spray directly at or into light fixtures and electrical outlets.
• Avoid using the pressure washer on very windy days to avoid damage related to overspray.
• Do not spray into gable-end vents, crawl spaces, or open eaves.
• Decks may also be cleaned with a pressure washer. The same rules apply, however, keep in mind the deck boards may be slippery.
• If the unit you rent is electrical, be sure a ground fault circuit interrupter (GFCI) is used to avoid a shock.
• Gasoline models are more mobile, but caution should be used in replacing gasoline when the engine is hot.
• Finally, Cabot suggests you practice on a surface which can not sustain damage like your concrete foundation. Practice makes perfect. Rest occasionally to avoid fatigue. Holding a unit at 2500 psi for a sustained period can be tiring.
• REMEMBER – NEVER POINT THE PRESSURE-WASHER WAND AT ANYONE!!
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