How it works, what it's good for, and why you shouldn't pressure wash your roof.
Soft washing is a cleaning method that uses low water pressure (under 500 PSI) combined with specialized cleaning solutions to safely remove dirt, algae, mold, mildew, and other organic growth from exterior surfaces. Unlike pressure washing, soft washing relies on the cleaning solution to do the work rather than water pressure.
The term started circulating in the early 2000s when exterior cleaning pros needed a way to describe what they were doing differently. They'd watched too many roofs and siding jobs get damaged by high-pressure washing and figured out that chemicals plus low pressure worked better.
Now it's the standard for roof cleaning. Shingle manufacturers like GAF and CertainTeed specifically recommend soft washing. They'll void your warranty if you pressure wash.
You spray a cleaning solution onto the surface at low pressure, and the chemicals kill organic growth at the cellular level. The pump delivers solution at 60-100 PSI, about the same as your garden hose.
Here's the typical process:
The technician inspects the surface and protects surrounding areas. Landscaping is pre-wet to prevent chemical absorption. Windows and other sensitive areas may be covered.
The soft wash solution is sprayed onto the surface using low-pressure equipment. The solution contains surfactants that help it cling to vertical surfaces and penetrate organic growth.
The solution is left on the surface for 5-15 minutes to work. During this time, the active ingredients kill algae, mold, and mildew down to the root. For roofs, no rinsing is done; rain naturally washes away the solution over the following weeks.
For house washing and most non-roof surfaces, the surface is rinsed with low-pressure water to remove the solution and dead organic matter. Landscaping is rinsed again as a precaution.
Professional soft wash solutions typically contain three main components:
Some jobs also call for sodium hydroxide (cuts through grease and oil) or sodium percarbonate (oxygen-based, gentler). Everything we use is biodegradable and breaks down into harmless stuff after application.
Soft washing is safe and effective for most exterior surfaces, including roofs, siding, stucco, brick, wood, and painted surfaces. Any material that could be damaged by high water pressure is a good candidate for soft washing.
Asphalt shingles, tile, slate, metal, and cedar shake. Soft washing is the only manufacturer-recommended method for roof cleaning. It removes black streaks, algae, moss, and lichen without damaging the roofing material.
Vinyl, aluminum, wood, fiber cement (Hardie board), and stucco. Soft washing removes green algae, mildew, and dirt without forcing water behind panels or damaging the surface.
Soft washing is particularly good for older brick where mortar may be deteriorating. It removes algae, efflorescence (white mineral deposits), and staining without damaging mortar joints.
Fences, decks, pergolas, and outdoor furniture. Soft washing cleans wood without causing splintering or raising the grain like pressure washing can.
You can also soft wash gutters, soffits, fascia, outdoor furniture, awnings, and screen enclosures. Pretty much anything that would get damaged by high pressure.
Soft washing uses chemicals to clean. Pressure washing uses force. Soft washing runs under 500 PSI; pressure washing hits 1,500-4,000 PSI.
Results from soft washing last 2-3x longer because the chemicals kill growth at the root. Pressure washing just scrapes off the surface layer, leaving spores behind that regrow fast.
For a detailed comparison of both methods, see our complete guide: Soft Wash vs Pressure Washing: Which Do You Need?
Yes, when done right. The chemicals are biodegradable and break down fast. But "done right" matters here.
We're using less pressure than a garden hose. No risk of water damage, no water forced behind your siding, no etching. The chemical concentrations are strong enough to kill growth but won't hurt your building materials.
We wet down landscaping before, during, and after the cleaning. At the dilution levels that reach your plants, the solution won't harm them. Keep pets inside during the job and until things dry (an hour or two).
Sodium hypochlorite breaks down into salt and water in sunlight. The surfactants are the same stuff in household cleaners. With proper dilution and rinsing, environmental impact is minimal.
Around Charlotte, expect to pay $200-$500 for house washing and $400-$1,000 for a roof. Size, accessibility, and how dirty things are all affect the final number.
What drives the price up or down:
Soft washing uses low water pressure (under 500 PSI) combined with specialized cleaning solutions to clean surfaces. Pressure washing uses high water pressure (1,500-4,000 PSI) to blast away dirt and grime. Soft washing relies on chemicals to do the cleaning work, while pressure washing relies on force. Soft washing is safer for delicate surfaces like roofs and siding, while pressure washing is better for hard surfaces like concrete.
Yes, soft washing is safe for plants when proper precautions are taken. Professional soft wash contractors wet down landscaping before and during the cleaning to dilute any solution that lands on plants. The cleaning solutions used are biodegradable and break down quickly. At proper dilution levels, plants are not harmed. Some contractors also cover sensitive plants during the cleaning process.
A typical soft wash house cleaning takes 1-3 hours depending on the home's size and staining severity. Roof cleaning typically takes 1-3 hours for most residential properties. Larger homes or properties with heavy organic growth may take longer. The actual application is relatively quick, but proper preparation (protecting landscaping) and thoroughness add time.
The primary chemical in soft washing is sodium hypochlorite (bleach) at concentrations of 1-3%, mixed with surfactants that help the solution cling to surfaces and penetrate organic growth. Some applications use sodium hydroxide or sodium percarbonate. All chemicals used in professional soft washing are biodegradable and break down into salt and water after application.
No, soft washing will not void your roof warranty. In fact, soft washing is the only cleaning method recommended by shingle manufacturers like GAF, CertainTeed, and Owens Corning. Pressure washing, on the other hand, can void your warranty because the high pressure strips away protective granules from shingles. Always use soft washing for roof cleaning to maintain your warranty coverage.
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