Pressure washing decision guides

Should you clean at all? Organic growth is worth removing: algae and moss hold moisture against the surface. General dust is not urgent, and Polymeric Exteriors Association guidance for siding treats mild soap and water from a garden hose as the routine method. Every aggressive clean is a small amount of wear you don't need to spend.

Which method? The surface decides, not your preference. Roofs: soft wash only, never pressure — ARMA is explicit that pressure washing asphalt shingles causes granule loss and very likely premature failure. Siding: soft wash, or pressure with caution and never angled upward. Wood: low pressure, 1,500 PSI per Fixr, with Today's Homeowner treating over 2,000 PSI as excessive. Sound concrete: pressure is fine, up toward Fixr's 3,500 PSI upper figure.

DIY or hire? DIY is reasonable for a ground-level concrete driveway or patio. Hire out roofs, second stories, delicate materials and any bleach-based work — Today's Homeowner warns those solutions can cause second- to third-degree burns. Fixr's professional rates are $50 to $150 per hour with a typical house at two to four hours, which is not a large premium against the cost of getting it wrong.

Timing against other work. If you're painting, staining or sealing, cleaning comes first and the surface must dry. Fixr advises washing a driveway before each resealing. If you're selling, clean before photography, not after listing.

When to say no. Say no to pressure washing a roof, to washing masonry in freezing weather (NPS advises against water cleaning when frost is likely), to a crew that won't put method and PSI in writing, and to an annual contract for surfaces that only need cleaning once.

How to choose

Clean for growth, not for dust

Algae and moss hold moisture and are worth removing. Light dust is a hose job. Every hard clean costs a little surface life.

Let the surface pick the method

Roof and wood: soft wash. Siding: soft wash or careful low pressure. Sound concrete: pressure. Your preference doesn't enter into it.

Draw the DIY line at the ladder

Ground-level concrete, fine. Anything on a roof or at height, or anything involving bleach solution, is worth the $50 to $150 per hour.

Wash before you coat, and let it dry

Painting, staining and sealing all need a clean, dry surface. Doing this out of order wastes the expensive part.

Be willing to walk away

No written method, no insurance certificate, offers to pressure wash the roof, or a same-day-only price. Any one of those is enough.