Dirt, mildew, and algae build up on your home’s exterior over time, making it look decades older than it is. A pressure washer strips all of that away in a few hours, restoring the original appearance without repainting. But too much pressure or the wrong technique can damage siding, force water behind walls, and strip paint you wanted to keep.

How to Power Wash Your House Exterior Safely

Choosing the Right Pressure Washer

Pressure is measured in PSI (pounds per square inch) and flow in GPM (gallons per minute). For house siding, you want moderate pressure and decent flow:

Vinyl siding: 1,300 to 1,600 PSI
Wood siding: 1,200 to 1,500 PSI
Brick and stone: 1,500 to 2,000 PSI
Stucco: 1,200 to 1,500 PSI (stucco is fragile — go easy)

A gas-powered washer in the 2,000 to 3,000 PSI range with an appropriate nozzle tip gives you enough power for any surface while allowing you to dial back for softer materials. Electric washers in the 1,500 to 2,000 PSI range work fine for vinyl and wood but may struggle with heavy buildup on masonry.

Nozzle Tips

The colored nozzle tips control the spray angle, which determines the effective pressure at the surface:

Red (0 degrees): A concentrated jet. Never use this on siding — it will gouge wood, crack vinyl, and blast mortar out of brick joints.
Yellow (15 degrees): Aggressive. Use sparingly on concrete and tough stains.
Green (25 degrees): The workhorse tip for most house washing.
White (40 degrees): Wide, gentle spray for rinsing and delicate surfaces.
Black (65 degrees/soap): Low pressure for applying detergent.

Start with the widest angle that works and only step down if needed. You can always increase pressure; you cannot un-damage siding.

Preparation

Walk the perimeter and close all windows and doors. Cover exterior electrical outlets and light fixtures with painter’s tape and plastic. Move outdoor furniture, grills, and potted plants away from the walls.

Trim any vegetation touching the siding so you can reach the wall surface. Protect delicate plants near the foundation with plastic sheeting if you are using a cleaning solution.

Connect a garden hose to the washer, fill the detergent tank, and test the spray on an inconspicuous area first — a section of siding behind a bush or on the least visible side of the house.

Washing Technique

Apply Detergent

Switch to the black (soap) nozzle. Spray cleaning solution on one section at a time, working from the bottom up. Bottom-up application prevents dirty detergent from running down dry siding and leaving streaks.

Let the detergent dwell for 5 to 10 minutes but do not let it dry. If it starts drying, mist the section with plain water.

Rinse

Switch to the green (25-degree) nozzle. Rinse from the top down, letting gravity carry the dirty water away. Hold the wand at a slight downward angle to the siding — never spray upward under lap siding, as water will get behind the boards and into the wall cavity.

Keep the nozzle 12 to 18 inches from the surface. Move in smooth, overlapping horizontal passes. Do not hold the spray in one spot.

Problem Areas

Mildew stains (black or green patches) often need a dedicated mildew cleaner or a bleach-based solution. Apply it with a pump sprayer before pressure washing, let it sit for 10 minutes, then wash as normal.

For rust stains from metal fixtures, use an oxalic-acid-based cleaner. Regular detergent will not touch iron oxide stains.

Surfaces to Avoid or Handle With Care

Windows: High pressure can crack glass or blow out glazing putty. Use the wide white nozzle and maintain at least 24 inches of distance.
Old painted surfaces: Pressure washing removes loose peeling paint efficiently, but it will also strip sound paint if you get too aggressive.
Roof shingles: Never pressure wash asphalt shingles. The force strips the granular coating and shortens the roof’s life dramatically.
Mortar joints: Older homes with lime mortar (pre-1930s) can lose mortar to pressure washing. Use low pressure and a wide nozzle.

Safety

Pressure washers are dangerous tools. The water jet can cut skin, and the kickback from a running wand can knock you off a ladder.

Never use a pressure washer on a ladder. The kickback is unpredictable. Use extension wands or telescoping wands to reach second-story siding from the ground.
Wear closed-toe shoes, safety glasses, and hearing protection.
Never point the wand at people, animals, or yourself.
Keep the spray away from power lines and electrical service entrance.

After Washing

Let the siding dry completely — at least 48 hours in dry weather — before painting or staining. Inspect for any damage the washing may have revealed: cracked siding, failed caulk, rotted trim. Now is the ideal time to make those repairs with the surface clean and visible.

A clean house exterior looks dramatically better and helps paint and stain last longer by removing the organic growth that traps moisture against the surface.