Power Washing Pros · 715-446-4271 · powerwashingproswittenberg.com
The short version
Decks and docks are cleaned at low pressure, with the grain, after a cleaning solution has loosened the dirt and killed the algae and mildew. The goal is clean wood, not stripped wood — high pressure furs up the fibers and gouges the soft grain. Cleaning is also the step that has to happen before any stain or sealer goes on.
Signs it's time
- Green or black on the boards, worst where it's shaded or near the water.
- Slick boards on the steps or the end of the dock.
- Grey, dull wood that used to be brown.
- Old stain peeling or wearing off in the traffic paths.
- Composite boards with dark spots or a dirty film.
Why decks get damaged by pressure washing
Wood has soft and hard bands in every board. A narrow, high-pressure stream cuts the soft bands faster than the hard ones, which leaves the surface ridged and fuzzy — furring. It can also etch lines into the boards and drive water deep into the end grain.
That damage is permanent until the boards are sanded. It is the most common way a deck gets hurt, and it is completely avoidable.
How it's cleaned instead
A cleaning solution goes on first and is given time to work on the dirt and growth. Then it's rinsed at low pressure, following the length of the boards. Rails, spindles, stairs and the fascia get the same treatment as the deck boards.
Composite decking is cleaned the same way. It doesn't rot, but it grows algae and mildew on the surface just like wood does, and it can be scarred by high pressure too.
Docks and boathouses
Lake-country docks live in the worst possible conditions for growth — damp, shaded, and splashed every day. They get slippery fast. Cleaning a dock is done with the water in mind; mention that the property is on a lake when you call, so the visit is planned around it.
Cleaning comes before staining
Stain and sealer need clean, dry wood to soak into. Putting a fresh coat over dirt, mildew and old grey fiber traps all of it under the finish, and the new coat fails early. Stain manufacturers' instructions start with cleaning for that reason.
After a wash, the wood has to dry thoroughly — usually a couple of days of good weather — before anything goes on. Staining and sealing are separate jobs from cleaning; ask about them on the call.
What to expect
A green, slippery deck comes out dramatically better. A deck that is grey from sun damage comes out cleaner and noticeably lighter, but the grey that is the wood itself stays — see the weathered-wood guide for what wood can and can't come back from.
What a wash will and won't do
Washing will
- Kill the algae and mildew that make boards green and slick
- Clean rails, spindles and stairs as well as the deck boards
- Get the wood ready for stain or sealer
Washing won't
- Replace sun-damaged grey fiber — weathered wood stays weathered
- Undo furring or gouges from an earlier high-pressure wash
- Fix loose boards, popped nails or rot