How to Clean and Power Wash Exterior Wood Siding

Weathered wood siding is often just dirty wood, hiding a vibrant finish under years of oxidation, mold, and dust. A thorough cleaning refreshes your home's curb appeal and, more importantly, prevents long-term rot by stripping away the organic matter that holds moisture against the fibers. When done well, the wood looks clean, even-toned, and ready for a fresh coat of stain or sealant. Power washing sounds aggressive, but it should be approached as a gentle rinse rather than a blasting session. The goal is to lift the grime without fraying the wood or driving water into the wall cavity. If you respect the grain and use the right detergent, you can transform the exterior of your house in a single afternoon without damaging the substrate.

  1. Clear the perimeter first. Move all patio furniture, grills, and potted plants at least ten feet away from the house. Cover any nearby delicate landscaping or light fixtures with plastic sheeting and painter's tape to protect them from cleaning solutions.
  2. Mix the right formula. Mix a concentrated wood cleaner or a mild oxygen bleach solution with water in a pump sprayer according to the manufacturer's label. Oxygen bleach is generally safer for wood and surrounding vegetation than chlorine-based alternatives.
  3. Spray bottom to top. Working in manageable ten-foot sections, spray the wood siding from the bottom up to prevent streaking. Let the solution dwell for about ten to fifteen minutes, but do not let it dry completely on the wood.
  4. Dial down the pressure. Attach a wide-angle nozzle (usually 40-degree or white tip) to your pressure washer. Keep the PSI below 1,500 for soft woods like cedar or pine to prevent gouging the surface.
  5. Rinse top to bottom. Starting from the top and moving down, use overlapping strokes to rinse the cleaning solution away. Follow the direction of the wood grain and keep the wand moving constantly to avoid leaving patterns.
  6. Let it dry completely. Give the siding at least 48 hours of dry, sunny weather to shed moisture before applying any stain or water repellent. The wood must be fully dry to prevent trapping moisture inside.