Person actively pressure washing an exterior surface with a high-pressure hose wand, illustrating the in-progress cleaning technique used on decks.
deck pressure washing — Pexels — Photo by Caitlin Whealy on Pexels — free to use, verify current license before real publication — locally optimized WebP, metadata stripped

A pressure washer can make a gray, mildewed deck look new again in an afternoon — or it can leave streaky gouges in the wood grain that no amount of staining will hide. The difference isn't the machine, it's the technique: pressure wash a deck the right way, at the right distance and pressure, and you clean it without damaging it.

How often to do it

Once a year is the standard rhythm for most decks — typically in spring, before the warm-weather season of grilling and foot traffic, and ideally before you apply any fresh stain or sealant. If your deck sits under heavy tree cover or in a shaded, damp spot prone to mold and mildew, a second light cleaning in fall can help, but a full pressure wash more than once or twice a year adds unnecessary wear to the wood fibers.

Before you start

  • Clear the deck completely — furniture, planters, grills, rugs.
  • Sweep off loose debris so you're not just blasting dirt and leaves into the wood grain.
  • Cover or move nearby plants, since some cleaning solutions and the runoff itself can stress landscaping.
  • Check the wood for loose boards, popped nails, or splintering before you add water pressure to the mix — repair those first.
  • Test an inconspicuous spot with your washer's lowest pressure setting before doing the whole deck, especially on softer woods.

Setting up the washer correctly

  1. Use a fan-tip nozzle, not a narrow, concentrated jet. A wide fan spray (25 to 40 degrees) spreads the pressure over more surface area instead of concentrating it into a line that can gouge wood fibers.
  2. Keep moderate pressure for wood. Composite and hardwood decking can generally tolerate more, but softer woods like cedar or pine need a gentler setting — when in doubt, start low and increase gradually rather than starting high.
  3. Hold the wand at a consistent distance, generally a foot or more from the surface, and keep it moving in smooth, overlapping passes rather than lingering in one spot.
  4. Always spray with the grain, following the direction of the wood boards, not across it — spraying across the grain is what drives water and dirt down into the fibers instead of off the surface.
  5. Work in overlapping strips from one end of the deck to the other so you don't miss sections or double up unevenly, which can create visible lines once the deck dries.

Cleaning solution and rinse

  • For mildew, algae, or general grime, a dedicated deck cleaning solution (or a mild oxygen-bleach-based cleaner) applied first and left to sit for the time the product recommends does more of the actual cleaning work than pressure alone.
  • Rinse thoroughly from the top of the deck down, working toward the stairs or the lowest point so dirty runoff drains away from the areas you've already cleaned.
  • Let the deck dry fully — this typically takes at least a day or two depending on humidity and sun exposure — before applying any stain or sealant. Sealing over damp wood traps moisture underneath the finish.

The takeaway

Pressure washing a deck once a year, with a fan nozzle, moderate pressure, and strokes that follow the wood grain, cleans without damaging. The washer itself isn't the risk — a narrow nozzle held too close and too long is what turns a routine clean into a repair job. When you're unsure, less pressure and more dwell time with a cleaning solution beats cranking up the PSI.

Derek Callahan
Editor

38-year-old licensed general contractor with 18 years in residential construction and repair. Derek spent over a decade as a union carpenter before going full-time into writing, and now tests every guide in his own century-old fixer-upper. Holds active residential contractor licensing in three states.