How To Clean Decks and Decking Tiles
by Pete Marentay
Deck cleaning is one of the most popular service performed by power wash contractors today. The most important factor in deck cleaning is surface preparation. Great surface preparation is the KEY to outstanding results. Prep right, and the deck will turn out GREAT. Rush through prep, skip a step (or two) to save money and/or time, and the deck wont look nearly as good.
Thorough cleaning of the deck or fence is essential to get good results. If the wood was previously sealed, you must strip off the old sealer rather than just clean the wood. If any old sealer remains, it might interfere with Ready Seal soaking into the wood. If the wood has not been sealed within the last five years, a deep cleaning is probably all that is needed. If you are not sure if the deck or fence must be stripped, a simple "splash" test is all you need to find out.
Sprinkle a little water from your fingertips on to the dry wood. If the droplets soak into the wood right away, you dont need to strip. If they form little droplets on the surface, you do have to strip.
High-pressure washing of wood is not necessary or advisable. Instead, use the proper-strength chemical cleaners to do all the work. Then you simply RINSE using your pressure-washer. Doing it the right way means using your pressure washer to agitate slightly with MODERATE pressure and HIGH water volume. Use the pressure washer responsibly. Too much pressure on the surface of the wood will cause furring damage.
Pressure washers are rated in PSI (pounds per square inch) and GPM (gallons per minute). The ideal pressure washer for cleaning wood will use at least 3-4 GPM (or more) at about 300 - 1000 PSI for most outdoor wood.
Since your pressure washer probably puts out 3000 PSI, you need to detune the pressure. There are three methods for reducing the pressure while keeping the volume of water. First one is to hold the tip farther from the surface of the wood. The pressure falls as the water is fanned out from the tip, so greater distance from the surface means less pressure reaching the surface. This is not a scientific adjustment, and is not the recommended method. The second way is to invest in a proper nozzle that will reduce the pressure to an acceptable range without restricting water flow. These nozzles can be purchased from Sun Brite Supply. The absolute BEST way to accomplish this reduction of pressure is to use a dual-lance wand (also called a chemical injection wand). This wand has a valve built-in that, when opened, allows water to be diverted to the second tube (or lance). With the chemical injector tip on that second tube (black in color) the water going through that tip has little or no pressure behind it. The more you open the valve, the lower the overall pressure delivered by the wand is. With this set-up, you can use low pressure for the deck and run full pressure to clean the driveway afterwards - without carrying a second wand or additional tips.
Cleaners and strippers have to be used carefully, too. Too much chemical or too much "dwell" time will cause the surface of the wood to develop "fuzzies".
Sun Brites SEVERE STRIP or REMOVE strippers can be applied through a DECKSTER sprayer, but can also be applied using a pump-up sprayer in an emergency. SBS sells Spray Doc pump-up sprayers in a model that is designed specifically for doing decks. It features a brass wand and tip that are easily adjustable, allowing you to fit the spray pattern to the job.
Allow either stripper to sit on the wood for about 10-15 minutes to loosen the dirt and/or the old sealer. When stripping, be careful to avoid getting caustics on any painted or aluminum adjacent surfaces. If you accidentally get stripper on one of these surfaces, rinse them gently as soon as possible. A caustic stripper will not damage latex if it is gently rinsed off.
Most contractors use REMOVE for the bulk of their work. If you run into a really tough finish that might take two strips to get done, you are usually better off using SEVERE STRIP. This is pretty strong stuff (almost three times as strong as REMOVE). The disadvantage in using a product this strong is the danger it presents to you if it gets on your skin. The real advantage is that it will strip almost anything the first time through. We dont recommend it for stripping acrylic finishes, for example, but during our field product tests SEVERE STRIP even stripped acrylic house paint off of rough-sawn cedar! Be careful out there.
Before applying a stripper to the deck, wet down the adjoining surfaces (such as plants, lawn, or house siding) with a hose. Minimize any water landing on the wood to be cleaned. Consider shielding plants and house siding with drop cloths to prevent contact with the detergent.
Use the pressure washer to "rinse" the surface. Avoid holding the nozzle too close to the wood or holding it in any one spot too long. Hold the pressure wand about 8" away from the wood and "sweep" it off in a rinsing motion. Use a "golf swing" motion, and avoid washing each square inch of the wood. Keep the wand moving smoothly over the surface to avoid leaving marks on the wood. Proper technique determines the results, so take some time to practice when you are able to.
Once the entire surface has been washed (and is still wet, but without puddles) apply Wood Britener to the wood with your DECKSTER sprayer. This will neutralize the pH of the wood and brighten it. You may let Wood Britener dry on the wood overnight without rinsing it off.
The wood is now clean, and it needs to thoroughly dry before it can be sealed (at least a day or two). As the wood dries, you will see a bright, clean, new-looking surface.