Power washing a deck is a quick and efficient way to get it ready for painting or staining, but it isn’t a necessary prerequisite. In fact, in some situations, it isn’t even a good idea, because power washing can chip and gouge wood. There are less aggressive alternatives to power washing that remove stains and surface discoloration, and if you don’t have success with any of them, you can always sand the deck.

The Importance of Cleaning

Before you apply any type of finish to a wood deck, you must remove any existing finish or there’s a good chance your new finish will fail prematurely. It will sit on top of the old finish instead of penetrating, and probably eventually peel off. If you’re staining an older deck, you also need to remove the gray surface layer of oxidation if you want the deck to appear anything like it did when it was new. A thorough cleaning of the deck also removes grime, dirt, tannin and rust stains and other blemishes that will show through the finish.

Advantages of Pressure Washers

The high-pressure spray from a power washer, also called a pressure washer, effectively wears off the surface layer of the wood, removing old finish, gray wood and stains in one fell swoop. It also removes debris from between the decking boards, which helps prevent the growth of rot and fungus. Because a pressure washer uses only water, it’s harmless to surrounding vegetation and introduces no noxious gases into the atmosphere. You don’t have to do any bending or scrubbing when you use a pressure washer, and unless you’re using it in conjunction with a deck cleaning detergent or you’re using a gas-powered model, you don’t need to buy any materials other than the pressure washer itself.

Using a Pressure Washer Properly

The main drawback of using a pressure washer is that the spray can be powerful enough to damage the decking wood. You can avoid this by using a tip with a wide fan width and holding it a uniform 3 to 6 inches from the wood. If under those conditions the spray doesn’t develop enough force to clean the deck satisfactorily, you have the option of scrubbing down the deck with a deck cleaner before you power wash. Some power washing rigs even allow you to add the detergent directly to the spray. You then spray lightly with detergent, wait for it to work, then wash again with high-pressure water.

Alternatives to Power Washing

If you’re staining a newly-installed deck, you probably don’t need to power wash it. Instead, mopping it with a deck cleaning solution and washing it off with a hose and water should be all the deck needs — if that. You can also use a cleaning solution in the same way on an old or dirty deck that could be damaged by high-pressure spray, although you will need to scrub the deck with a stiff brush after letting the solution sit for a few minutes. In some cases, sanding is a better alternative than power washing, because it flattens and smooths weathered boards while removing the old finish. If your deck is larger than 100 square feet, you can save time and effort by renting a flooring orbital sander to do the job.