What Surfaces Should You Never Pressure Wash? A Material-by-Material Guide

Gorilla Kleen Exterior Cleaning · Sarasota & Manatee County, FL

Which Surfaces Should You Never Pressure Wash?

Never pressure wash asphalt shingles, painted stucco, EIFS, wood siding and decks, brick and mortar, or window and pool screens. In this guide, “pressure washing” means running a pressure washer at full power. A few of these materials allow a gentle rinse, and the table below shows exactly how gentle, using each manufacturer’s or trade group’s own number.

If you’re deciding what you can safely do yourself, start with our guide to what’s safe to pressure wash yourself. Concrete driveways and pavers sit at the other end of the scale; see pavers and concrete.

Limits come from each manufacturer’s or trade group’s published care guide, listed under Sources. Check your own product’s guide first. For machine settings on the surfaces that can take pressure, see how to set pressure for each surface.

Can You Pressure Wash a Roof?

Not if it’s asphalt shingle. The Asphalt Roofing Manufacturers Association (ARMA) says high-pressure washing is likely to damage asphalt roofing, and tells homeowners not to use a power washer, brush, or broom to clean algae off it.

Asphalt shingles

Shingles are covered in mineral granules that shield the asphalt from the sun. A pressure washer knocks those granules loose, and the shingle ages faster once they’re gone. Shingle maker GAF tells its contractors to warn homeowners that pressure washing could damage their shingles and that roof cleaning is best left to professionals.

ARMA’s own method is a diluted household bleach solution applied without a power washer. It notes the stains can return, and that other chemicals shouldn’t be used without the shingle maker’s approval. Those black streaks are usually algae; we explain what the black streaks on your roof are and why Sarasota roofs grow them so fast.

Gorilla Kleen’s soft wash roof cleaning in Sarasota uses that low-pressure approach: the cleaning solution kills the growth, and the rinse stays at low pressure.

Concrete tile

Concrete tile tolerates more than shingles. Eagle Roofing Products, which makes concrete roof tile, recommends plain water at no more than 1,200 psi, and says the job should go to a licensed, bonded, insured roofing contractor with tile experience. Walking a roof is risky, and water makes it worse. If a cleaner is needed, Eagle says to use the most diluted solution that works and to pick one that’s compatible with concrete, since some products can change the tile’s pH or etch the surface.

Can You Pressure Wash a Stucco House?

Not at full pressure. Sto Corp.’s maintenance guide for acrylic stucco finishes says to wash at 200 to 500 psi with the nozzle several feet from the wall, and never above 500 psi.

Painted or acrylic-finish stucco

If your stucco is painted or has an acrylic or elastomeric finish coat, the Sto limit applies. Above 500 psi, Sto says the finish’s surface can be destroyed. Stiff brushes, wire brushes, and steam are off the list too.

Unpainted cement stucco

Bare cement stucco takes a little more. Lowe’s lists 1,200 to 1,500 psi with a 40-degree tip, and a 25-degree tip only if unpainted stucco needs more cleaning power. Look for cracks before anyone sprays: water driven into a crack ends up behind the wall surface, where you can’t see it.

EIFS (synthetic stucco)

EIFS looks like stucco but is a thin finish over foam insulation board. Sto caps washing at 500 psi, because higher pressure can destroy the surface.

Gorilla Kleen soft washes stucco as part of every house wash for stucco and siding, so the finish never sees high pressure.

Is It Safe to Pressure Wash Wood Siding or a Wood Deck?

Rarely at full pressure. The USDA Forest Products Laboratory warns that power washing can remove wood from the surface, especially on softer woods such as western red cedar.

On wood, a cleaner and a soft brush should do the work, with water only for the rinse.

Painted wood and lead paint

High pressure peels paint and pushes water behind the boards. On an older house, there’s a bigger problem: Lowe’s tells homeowners not to pressure wash a home they think was painted with lead paint, which usually means paint applied before 1978. Get the paint tested before anyone sprays it.

Fiber cement and vinyl

Neither one is a “never.” James Hardie allows a pressure washer on its fiber cement siding below 1,500 psi, with a wide fan tip held at least 6 feet from the wall, and says damage from improper cleaning may not be covered by its warranty. On vinyl, aim the spray straight at the wall, never upward under the laps, which drives water behind the siding.

Can Pressure Washing Damage Brick or Mortar?

Yes. The Brick Industry Association’s cleaning guide, Technical Note 20, caps water pressure at 400 psi at the nozzle unless the brick maker allows more, with the tip held at least 12 inches from the wall.

Pressure bands from BIA Technical Note 20, Cleaning Brickwork (August 2018).

BIA also calls for a 25- to 50-degree fan tip. Above those limits, it says, pressure can etch mortar joints and strip the outer surface of the brick, and that damage is permanent. Some retail how-to guides list 1,500 to 2,000 psi for brick. We follow the brick industry’s number.

Can You Pressure Wash Window Screens or a Pool Cage?

No. Pool and patio screen mesh is about 0.013 inch thick, and a pressure washer tears it. Lowe’s also says to keep high-pressure spray away from windows.

Screen enclosures get a soft wash and a gentle rinse, with the screens left in place. We cover the full process in our guide to how we clean pool cages.

What Else Around the House Shouldn’t Get Sprayed?

Keep the wand off anything that holds electricity, lets water inside, or grows:

• Windows and exterior vents, which Lowe’s singles out
• Outdoor outlets, light fixtures, and the electric meter
• Door and window weatherstripping
• Irrigation heads and exposed sprinkler lines
• Plants and flower beds, especially when detergent is in the mix
• People and pets, above all with a zero-degree nozzle

What Should You Use Instead of Pressure Washing?

Soft washing. Gorilla Kleen is certified in the Soft Wash system: a cleaning solution goes on at low pressure, stays long enough to kill mold, mildew, and algae, then gets a gentle rinse.

Gorilla Kleen uses biodegradable, EPA-compliant detergents, and its equipment collects and recycles wash water so it doesn’t run into storm drains. See the cleaning solutions we use.

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