It's a common question as you look at your weathered wooden benches: can I just blast the dirt away with a power washer? The short answer is: it's risky and generally not recommended. While a power washer is incredibly effective on concrete and composite materials, its high-pressure stream can be far too harsh for wood.
Wood is a porous, fibrous material. The intense pressure from a power washer can easily gouge the soft grain, creating splinters and rough patches. It can force water deep into the wood, beyond where it can quickly evaporate. This trapped moisture leads to swelling, warping, and creates a perfect environment for mold and mildew to grow, ultimately shortening the life of your bench.
For routine cleaning, gentler methods are far superior. Start by brushing off loose debris. A simple solution of warm water and mild dish soap or a dedicated wood cleaner applied with a soft-bristle brush is highly effective. Scrub in the direction of the grain, then rinse thoroughly with a garden hose on a gentle "shower" setting. This method cleans effectively without damaging the wood's surface.
If you must use a power washer for heavily soiled benches, extreme caution is required. Use the widest, lowest-pressure tip (40-degree white tip or wider), keep the nozzle at least 12-18 inches away from the wood surface, and never hold it perpendicular—always spray at an angle. Keep the wand moving constantly to avoid concentrating pressure on one spot. Afterward, allow the wood to dry completely for several days before applying a fresh sealant or stain to protect it.
Ultimately, preserving your wooden benches is about maintenance, not force. Regular gentle cleaning and periodic sealing with a quality wood protectant will keep them looking beautiful for years, without the hidden damage caused by high-pressure water.