How to Pressure Wash a House: PSI, Nozzles, Soap and Order

Start at the low end of each range with the widest tip that works, at the far end of the distance range, and move closer only if dirt is not lifting. The siding or surface maker's care instructions override these general figures, which come from pressure washer manuals and surface manufacturers.

Nozzle tips are color coded by spray angle. A narrower angle concentrates the same pressure on a smaller spot, so the tip matters as much as the PSI rating. For siding, the 40 degree white tip is the default, the 25 degree green tip is for stubborn spots at a distance, and the black soap tip applies detergent. The red 0 degree tip has no place on a house.

Use detergent. Pressure alone moves loose dirt, but the green and black film on north walls is mildew and algae, and it comes back quickly unless a cleaner kills it. Soft washing is cleaning with a cleaning solution at low pressure, letting chemistry do the work instead of force. It is the method shingle makers and many siding makers recommend, and it is the safe approach for stucco, painted wood and roofs.

• House wash detergent through the washer: fill the onboard tank or siphon tube, fit the black soap tip, and apply. Only use detergents labeled for pressure washers, since other chemicals can damage pump seals, and never run bleach through a pump unless the washer manual allows it.
• Pump sprayer soft wash: a no-rinse cleaner such as Wet & Forget Outdoor Cleaner Concentrate (128 oz.) goes on with a pump sprayer like the Chapin 25012 Clean N Seal 1-Gallon Deck Sprayer and works over weeks as weather rinses it, with no pressure washer at all. It suits homeowners who want to avoid ladders and high pressure entirely.
• Dwell time: leave detergent on for the time on its label, and do not let it dry on the wall. Work in shade or in sections on warm days.
• Plants: soak shrubs and flower beds with plain water before and after applying cleaner, and cover delicate plants with plastic sheeting if the label calls for it.

Follow every cleaner's label for dilution, protective gear and plant safety. Wear eye protection and gloves when handling concentrates.

Both, at different stages. The common sequence in washer manuals and detergent labels is:

• Pre-rinse top down with plain water to wet the wall and knock off loose dirt and cobwebs.
• Apply detergent bottom up. Starting at the bottom prevents soap running down over dry siding, which leaves clean streaks that are hard to blend later.
• Rinse top down, so the dirty runoff flows over areas you have not finished rinsing yet rather than over clean siding.

Work one wall section at a time, roughly the width you can reach without moving the washer, and overlap each rinse pass. On vinyl and other lapped siding, hold the wand level or angled down so water hits the face of each lap and runs off, rather than being forced up behind it. For second-story walls, use an extension wand or a telescoping pole from the ground; an EXTEND-A-REACH 5 to 30 ft. Telescoping Extension Pole with a soft brush handles high spots without a ladder. If a spot cannot be reached safely from the ground, hire a professional soft washing service.

Water under pressure finds every gap. Before washing:

• Close all windows and doors and check that window seals and caulk are intact. Rinse glass from a distance with the 40 degree or soap tip rather than aiming at it, and never spray directly at window frames, where water is forced past weep holes and seals.
• Cover exterior outlets, light fixtures, doorbells and cameras with plastic sheeting and painter's tape. Never spray into an electric meter, service panel or wall-mounted electrical box.
• Do not spray into dryer vents, bathroom fan vents, soffit vents or gable vents. Water inside a vent can soak insulation and wiring.
• Air conditioner condensers: keep high pressure off the fins, which bend easily. A garden hose is the right tool there.
• Move cars, grills and patio furniture out of the overspray zone, and remove hanging planters and decorations.

If the house was built before 1978, EPA guidance is to test peeling or chalking paint for lead before any pressure washing, because blasting lead paint spreads contaminated chips across the yard. Loose paint on any house means pressure will strip more of it.

For siding alone, electric is enough. Siding needs 1,300 to 1,600 PSI, which every electric in the catalog exceeds. The limit of electrics is flow: many deliver 1.2 GPM, which rinses slowly on a big house. The Greenworks 3000 PSI 2.0 GPM Brushless Electric Pressure Washer at 2.0 GPM closes most of that gap, and the Kärcher K 5 Premium Electric Pressure Washer with Hose Reel adds a hose reel and a water-cooled induction motor at 1.4 GPM. Electrics start with a switch, run quietly, have no fumes and store on a shelf.

Gas makes sense when the same machine also cleans a long concrete driveway, a large patio or fences, where 2.3 GPM or more and a surface cleaner save hours. The Westinghouse WPX3400 3400 PSI 2.6 GPM Gas Pressure Washer (3,400 PSI, 2.6 GPM) and Simpson Clean Machine 3400 PSI 2.5 GPM Gas Pressure Washer (3,400 PSI, 2.5 GPM) are value gas machines, while the Simpson PowerShot PS3228 3300 PSI Honda GX200 Gas Pressure Washer with its Honda engine and triplex pump is built for years of heavy use. Turn a gas unit down for siding with the 40 degree tip and more distance. The full comparison is on electric vs gas pressure washers.

Wand cleaning speed scales with flow. These planning estimates use the site's shared surface rates (square feet per minute per GPM) and do not include setup, detergent dwell time or moving the washer.

If the job includes a driveway, patio or walkway, yes. A surface cleaner is a round housing with a spinning spray bar that holds the nozzles at a fixed height over flat concrete, so it cleans evenly without the zebra stripes a wand leaves and cuts the time substantially. The Westinghouse 15 in. Pressure Washer Surface Cleaner ($39.99) fits washers with a 1/4 inch quick connect up to 3,400 PSI. Surface cleaners work best with 2.0 GPM or more; on a 1.2 GPM electric they spin slowly and clean slowly.

Treat oil stains with a concrete degreaser before washing. Wash pavers gently and plan to re-sand joints with polymeric sand such as Alliance Gator Supersand G2 Polymeric Sand (50 lb) once they dry completely, since pressure strips joint sand. Surface cleaners are for flat horizontal concrete and pavers only, never siding or wood decks.

• Asphalt shingle roofs. Pressure strips the protective granules and many shingle makers warn it can affect the warranty. Roofs get a low-pressure soft wash by a professional.
• Anything from a ladder. The recoil of the wand can push you off balance, and a fall with a live wand is doubly dangerous. Use extension wands from the ground.
• Electrical equipment: meters, panels, outlets, light fixtures, pool equipment and AC condenser fins.
• Old or soft mortar, and painted surfaces with loose paint, which pressure will erode or strip.
• Windows at close range and insulated glass seals.
• Stained glass, screens, cedar shakes and other delicate trim.
• People, pets and plants. Never point the wand at anyone, even as a joke.