A season of rain, snow, and grime leaves a visible film on siding, decking, and concrete, and it's more than cosmetic. Mold, mildew, and algae don't just look bad, left alone they slowly work into the surface underneath and cause real damage over time.
Why it matters
- It protects the surface, not just the look. Mold and algae hold moisture against siding and wood, which can lead to staining, rot, and deterioration if it's never cleaned off.
- It's a safety issue on decks and patios. A film of algae or mildew on a walking surface gets slippery, especially once it's wet, so clearing it off is as much about traction as appearance.
- It sets up any staining or painting project right. If you're planning to reseal a deck or repaint trim this year, a clean surface is what makes that finish actually stick and last.
- It's one of the fastest curb appeal wins available. A clean exterior makes a home look cared for, which matters whether you're just enjoying your own place or getting ready to list it.
Use the right pressure for the surface
More pressure isn't automatically better, too much can etch concrete, strip paint, splinter wood, or force water behind siding where it doesn't belong. General starting points:
- Wood deck: 1,200 to 1,500 PSI, spraying in the direction of the wood grain with a wide-angle nozzle, keeping the wand at least 8 inches from the surface
- Composite deck: up to about 2,000 PSI, composite generally tolerates more than natural wood
- Vinyl siding: 1,300 to 1,600 PSI, spraying top to bottom and always angled downward, never upward or directly into the seams where panels overlap, holding the wand 3 to 4 feet away
- Concrete patio or driveway: concrete tolerates more pressure than siding or wood, but still test an inconspicuous area first and keep the wand moving to avoid etching
When in doubt, start on the lower end of the range and test a small, hidden spot before doing the whole surface.
A word on safety
Pressure washers send emergency rooms thousands of visitors every year, they're a genuinely powerful tool and worth respecting. Keep the nozzle away from skin, never point it at another person, and be extra cautious near outlets, light fixtures, and anything electrical.
When to call a professional
Bring in a pro if your home was built before 1978 and you're dealing with painted exterior surfaces that could involve lead paint, if you're not confident about the right pressure for a delicate surface, or if you'd simply rather not take on the risk of causing damage yourself. A professional crew also has the equipment to manage runoff and debris properly.
