Can you pressure wash old brick or stone? What the National Park Service advises

Updated November 10, 2026 · KeystoneProGuide editorial team

Can old brick or stone be pressure washed?

Only gently, and only after a test. The National Park Service recommends always using a low-pressure spray of 100-400 psi, controlled through a hose and wand held at least 12 inches from the surface, and testing the method on a small, inconspicuous area first. It warns that some historic materials can easily be damaged even at those low pressures.

The gap between that advice and ordinary equipment is large. The Park Service says most power-washing equipment found in hardware stores operates at potentially damaging pressures of 1600-3200 psi.

Why is old brick so easily damaged?

Because its hard face protects a softer inside. The Park Service says low-fired historic brick tends to have a soft, porous interior beneath the protective fire skin, and that excessive pressure can remove surface material and scar historic stone, brick or concrete.

Mortar is a second weak point. The Park Service lists lime-based materials, including mortars, stuccoes and limewash, among sensitive materials. Porosity is a third: it says soft brick and stone are porous, so graffiti can soak into them and leave a ghost even after removal.

How old is "old"?

The Park Service writes about historic buildings and does not set a year. For a sense of how much housing is involved, the Census Bureau estimates that 25.0 percent of Pennsylvania's homes, and 39.9 percent of Philadelphia's, were first built in 1939 or earlier. The age of a wall is only a guide; the condition of the brick and mortar is what decides how gently it must be treated.

The Park Service suggests questions to ask before cleaning any historic surface: is it soft, is it powdery or "sugaring", and are there signs of decay? If the answer to any of those is yes, its warning that some materials are damaged even at low pressure applies with full force.

How should a test be done?

The Park Service gives two sizes. For trying products and techniques, it suggests patches of six inches by six inches or less, in inconspicuous areas, with several people judging the results and any damage before a method is chosen. For pressure washing historic masonry, its article on oil contamination suggests a 36 by 36 inch patch in a less conspicuous area before large-scale cleaning, and says even 200-500 psi may be too much for some materials.

It also lists what changes the result: pressure, volume, temperature, nozzle pattern, the angle of the spray, water quality, operator skill and any chemical additives. That is why it says spraying should be done by professionals who understand those variables.

Are chemical cleaners safer than pressure?

Not automatically. The Park Service says alkaline cleaners are generally not recommended for sensitive stone such as limestone or marble. Where an alkaline product is used on masonry, it says the surface should be wetted first, the cleaner rinsed from the bottom up, and a neutralizer applied afterward to stop damage. It also says to read the product literature and safety data sheets, follow the maker's recommendations, and never use a product off label.

What about painted brick?

Painted masonry on a house built before 1978 adds the federal lead rule. The U.S. Environmental Protection Agency requires anyone paid to disturb painted surfaces on such a home to be certified in lead-safe work, and its archived guidance says washing must be contained so that dust and debris, including in the waste water, stay in the work area.

Do the trade bodies agree?

Not entirely. The vinyl siding industry's association, PEPA, in a table comparing cladding, describes brick as requiring "re-pointing of mortar and pressure washer for cleaning". That is a siding trade body's comparison, and it sits uneasily beside the Park Service's caution about old masonry. PEPA's own cleaning advice does respect brick in one way: it says to cover brick or stone accents to protect them from runoff when siding is washed. Where the two differ on older masonry, this guide follows the Park Service.

Does Philadelphia require approval?

For some houses, yes. If your property is on the Philadelphia Register of Historic Places, the Historical Commission requires review for masonry cleaning, painting, pointing and related work. The review is free, and staff can be reached at preservation@phila.gov. The Philadelphia guide covers the city's other rules.

What does it cost?

Angi gives $0.10 to $0.40 a square foot to pressure wash brick. Fixr's highest case, $2,000, is specialty pressure washing of a 2,500-square-foot brick home with severe grime. No survey prices gentle, low-pressure cleaning of historic masonry separately, so ask each company what pressure and method its price assumes.

What should you ask a company?

• What pressure will you use on the brick, and will you test a patch first?
• What cleaner, if any, and is it suitable for my brick or stone?
• How will you protect the mortar joints?
• Do you know whether my house is on the historic register?

Soft washing vs pressure washing explains why low pressure keeps coming up, and how to choose a pressure washing company covers the other checks. Businesses offering the service are on the pressure washing directory page.

Sources

1. Preservation Matters: Maintenance - Graffiti Removal from Historic Features, National Park Service
2. Protecting Historic Structures from Oil Contamination, National Park Service
3. How to Clean Vinyl Siding, Polymeric Exterior Products Association (PEPA)
4. Get approval for work to a historic property, City of Philadelphia
5. 2020-2024 ACS 5-Year Narrative Profile: Pennsylvania, U.S. Census Bureau
6. 2020-2024 ACS 5-Year Narrative Profile: Philadelphia County, Pennsylvania, U.S. Census Bureau
7. Lead Renovation, Repair and Painting Program, U.S. Environmental Protection Agency
8. How Much Does It Cost to Pressure Wash a House? [2026 Data], Angi
9. How much does it cost to pressure wash the exterior of a house?, Fixr