Power Washing wood substrates/surfaces

NEVER do it!

There are several techniques that have been around for years that avoid power washing of wood surfaces altogether.

It pains me to see "professionals" still using power washers to clean wood decks, wooden walls and all other wood surfaces. In my travels around the world, I've seen monuments, floors/decking, siding and other surfaces torn apart by a good intentioned pressure cleaner who simply doesn't know better.

If you were able to look at a wood surface through a microscope, you would see fibrous grains that make up the structure. A power washer lifts the grain on the surface of wood. Even on a microscopic level, the damaged (lifted) fibers become wicks for moisture as well as traps for particulates that feed and start mold. In essence, power washing lessons the life expectancy of the wood and in many cases ruins the aesthetics.

How should you prep wood surfaces? Chlorine! Be careful around plants and wear gloves and clothes you're willing to throw away! Dilute the chlorine to a 50/50(water) solution in a pump sprayer and spray surfaces to be cleaned. Let sit until mold becomes light brown and starts breaking down. Some light scrubbing may be needed, but mostly a simple rinse with water will remove particulates and "KILL" the mold. (repeat as necessary). (we are also assuming the wood surface was put together with the proper anti corrosive hardware (ie. screws/anchors))

I've walked away from countless jobs because the homeowners argued "they have ALWAYS done it with a power washer in the past, and it looked like new wood!" 2 things - The "new wood look" was less several layers of the old wood, leaving them with a splintering hazard that would quickly waist away. Next, I had no problems doing the correct thing for the federal/state/local government entities as well as the National and Regional chains that sought me out for doing the right thing.

If a "New look" is what you're after, there are several ways to attain it.

-Replace the wood.
-Have a contractor set all nails and screws and properly sand the surface past the aged (gray) surface. - quickly treat and protect the sanded surface.
-Chemically clean the surface and find a stain that will highlight the natural grains in the wood.
-For new wood, apply an appropriate UV and waterproof treatment (as often as recommended by the manufacturer.

Even if the manufacturer's label suggests power washing the wood surface.....don't do it. A chemical treatment will not only kill the mold (simply power washing will not remove embedded spores) it will save you years on your surface's life.