That's an excellent and practical question! The short answer is: it depends entirely on the bench material. Pressure washing can be a fantastic time-saver for cleaning outdoor furniture, but using it incorrectly can cause irreversible damage.
For durable materials like concrete, stone, or certain powder-coated metals, pressure washing is generally safe for regular cleaning. Use a wide-angle tip (40-degree), maintain a good distance (at least 12-18 inches), and avoid the highest power setting. This effectively blasts away dirt, mildew, and pollen without harming the surface.
However, for wooden benches—especially softer woods like pine—high-pressure water is a major risk. It can splinter the wood, drive moisture deep into the grain (causing warping and rot), and strip away protective stains or sealants. For wood, a gentler approach with a garden hose, soft brush, and a dedicated wood cleaner is always safer.
For benches made of recycled plastic or resin, check the manufacturer's guidelines. While many are designed to be low-maintenance, a high-pressure stream can sometimes cause pitting or surface etching over time.
Best Practice Tip: Always test in an inconspicuous area first. Start with the lowest pressure setting and increase gradually only if needed. When in doubt, opt for manual cleaning to preserve your bench's longevity and appearance. Regular, gentle cleaning is often more effective and safer than infrequent, aggressive power washing.