How to Power Wash a House Exterior

Set up for 1,300-1,600 PSI on vinyl, aluminum, or painted wood — the range most electric washers deliver — and step up only for bare brick or concrete. Start with the 40-degree (white) tip and switch to the 25-degree (green) only for stubborn grime on tough surfaces; the zero-degree red tip has no business on a house. If you're renting, say what siding you have and the counter will size the unit; bigger is not better here.

Close every window and storm window, cover exterior outlets, light fixtures, and dryer vents with plastic sheeting and painter's tape, and pre-soak plantings with plain water before draping tarps loosely over them — dry leaves absorb drifting detergent. Walk the walls first and note loose, cracked, or gapped siding: high-pressure water finds every defect, so repair damaged vinyl panels before you wash, not after the wall cavity is wet.

Fit the low-pressure soaping tip (usually black), draw house-wash detergent through the washer's injector, and coat one wall working from the bottom of the wall upward — bottom-up prevents the clean streaks that happen when soap runs down a dry, dirty wall. Work in a section you can rinse before it dries, roughly one wall face at a time, and keep the coat wet-looking.

Give the soap 5 to 10 minutes to break down the grime, algae film, and mildew. The one rule: it must stay wet the whole time, because dried detergent bakes streaks onto siding that take twice the work to remove. On a hot or windy day, work smaller sections, keep out of direct afternoon sun where you can, and mist the wall with plain water if the soap starts flashing dry.

Swap to the 40-degree tip and rinse starting at the top of the section, sweeping side to side and letting the dirty water sheet down over the unrinsed area below. Keep the wand near eye level and the stream angled level or slightly downward — never upward, which drives water behind the siding laps and into the sheathing where it feeds mold you'll never see. Start 8 to 10 feet back and step in only as needed; distance is your pressure control.

Treat each wall face as its own soap-dwell-rinse cycle rather than soaping the whole house at once. Overlap each rinsing pass by a third of the fan width so you don't leave zebra stripes, and keep the wand moving — hovering on one spot etches a clean patch that shows forever. Check your work from 20 feet back after each wall; streaks invisible up close jump out at driveway distance.

The green film on north-facing walls and the black speckles under roof overhangs are alive, and pressure alone just gives them a haircut. Pre-treat those areas with an oxygen-bleach house wash applied by pump sprayer, let it work 10 minutes, agitate stubborn patches with a soft-bristle brush on a pole, then rinse. If the specks survive, treat again rather than cranking the pressure — chemistry kills growth, force doesn't.

Some exteriors fail catastrophically under pressure. EIFS synthetic stucco (it sounds hollow when tapped) lets forced water behind the foam where it rots the structure invisibly — soft wash only. Homes painted before 1978 with chalking or flaking paint are a lead hazard: pressure washing scatters contaminated chips and wastewater, and remediation rules apply. Brittle asbestos-cement shingles from the same era release fibers when blasted. Old lime-mortar brick loses its joints to high pressure, and once they are washed out the fix is repointing the mortar joints, not a gentler second pass. When your house is on this list, the answer is chemistry, gentleness, or a specialist — not a bigger machine.