Pressure washing your exterior wood or decks. Is it safe for the wood? Will it damage the wood cell structure? The answer is Yes and No! Taking the proper steps can save your wood from being permanently damaged!

It is never safe and/or recommended to pressure wash a deck while using just the water pressure. Pressure washers can have a range of PSI (pound square inch) from 1600 to 4500 PSI! If using just water the pressure can tear at the wood fibers and destroy the Lignin. Lignin is found in all vascular plants, mostly between the cells, but also within the cells, and in the cell walls. In wood it is very resistant to degradation, being held together with strong chemical bonds. By using an excess amount of pressure though, damage to the lignin happens and it is separated from the wood fibers.

Pressure washing as a rinsing tool is a different matter. When using the appropriate deck cleaner or deck stripper, you are able to use the pressure washer  for rinsing or light washing. The deck cleaners and deck strippers "soften" the layer of dirt, grime, mildew, and or previous coatings. By softening the bond between the wood and "grime" you are able to use your pressure washer at a reduced amount of pressure. You can either dial down your pressure or wash from a distance of 8-12" away. When you are at that distance you are using about half of the amount of pressure that your system is rated for. Some extra tips when washing:

• Washing with a pendulum motion. Similar to sweeping a broom. Over exaggerate until you get the hang of it.
• Use a fan tip. Usually the 25(green) or 40(white) degree tip. Never the red, zero point tip!
• Never stop and reverse direction when directly above the wood. This can cause a "stop" line, which is a small dent.

There isn't any reason why you shouldn't use a pressure washer when cleaning your deck or exterior wood. Just make sure that you use the correct deck cleaner or stripper. This will make your project easier and safer for your wood!