Pressure Washing 101: What to Wash, What to Avoid

Few things are as satisfying as watching years of grime peel off a driveway under a pressure washer. But that same power can carve lines into wood, blast paint off siding, force water behind stucco, and strip the granules off a roof. The difference between a great result and an expensive mistake comes down to knowing what to pressure wash, what to never point a wand at, and how much pressure each surface can take.

These pressure washing tips cover the basics: PSI by surface, the power washing dos and don'ts, and where soft washing is the safer choice. NorTech connects Bay Area homeowners with independent, vetted, background-checked, insured providers when you would rather not rent the machine at all.

PSI basics: pressure is not a one-size setting

PSI measures the force of the water; GPM measures the volume. More PSI is not better, it is just more aggressive. The right approach starts low, tests in a hidden spot, and increases only as needed. As a rough guide: concrete and brick tolerate high pressure, wood and pavers need a gentler touch, and painted or delicate surfaces need very little, if any, direct pressure.

• Concrete driveways and walkways: high pressure is generally fine, around 3000 PSI with the right nozzle
• Brick and unpainted masonry: moderate to high, but test first for loose mortar
• Wood decks and fences: low pressure and a wide fan tip, keeping the wand moving
• Pavers: moderate pressure, mindful of blowing out the joint sand
• Cars, windows, screens, and anything painted: low pressure or hand washing only

What to pressure wash

Pressure washing shines on hard, durable, flat surfaces: concrete driveways, walkways, patios, brick, and stone. Pressure washing a driveway is the classic project and the easiest win. Keep the nozzle a steady distance from the surface, use overlapping passes, and work in one direction to avoid streaking.

What to avoid: when to soft wash instead

This is where most homeowners get into trouble. Do not pressure wash your roof, your siding, stucco, or anything with paint or sealant you want to keep. Roofs and many exterior walls should be cleaned with soft washing, a low-pressure method that uses cleaning solution to break down algae and mildew without driving water behind the surface or stripping material. Pressure washing a house exterior at full force can force water into walls and cause hidden moisture damage that costs far more than the cleaning saved.

Tools and materials you will need

• A pressure washer sized to the job (electric for light work, gas for driveways)
• A range of nozzle tips, from wide fan to turbo, and a surface cleaner attachment for flat concrete
• Eye protection and closed-toe shoes; the spray can throw debris and injure skin
• Appropriate detergent for the surface
• Painter's tape and plastic to protect outlets, light fixtures, and nearby plants

Step-by-step for a driveway

Sweep first and pre-treat oil stains. Wet the surface, apply detergent, and let it dwell without drying. Then make slow, overlapping passes with a consistent nozzle distance, working with the slope toward the drain. Rinse thoroughly. A surface cleaner attachment gives a far more even result than waving the wand by hand.

If a surface can be dented, faded, or pried loose, it probably should not see full pressure. When in doubt, soft wash it.

Common pressure washing mistakes

• Using too high a PSI on wood, pavers, or painted surfaces
• Holding the nozzle too close, which etches concrete and gouges wood
• Pressure washing siding or roofs that should be soft washed
• Spraying upward under siding or into vents, forcing water inside the wall
• Ignoring eye protection; the spray and flung debris cause real injuries

When to call a pro

Hire a vetted, insured provider for two-story exteriors, roofs, anything that needs soft washing, and large jobs where renting and hauling a gas machine is more hassle than it is worth. A pro brings the right pressure and chemistry for each surface and carries insurance if something goes wrong. If you are weighing renting versus hiring, our DIY vs hire a pro guide helps.

Pressure washing booked through NorTech is covered by a 72-hour Satisfaction Guarantee, so if you are not happy with the result within that window it gets made right at no charge. You can browse pressure washing to see what a matched provider handles.