Soft washing is a cleaning method that uses low water pressure, typically under 500 PSI, combined with a cleaning solution to break down and kill organic growth such as algae, mildew, and mold. Unlike pressure washing, which relies on mechanical force to blast away surface contamination, soft washing treats the root cause of biological growth and then rinses it away gently. It is the correct method for roofs, vinyl siding, painted wood, and other surfaces that cannot tolerate high pressure.
How soft washing actually works
The cleaning solution in a soft wash system does the heavy lifting, not the water. A mixture of sodium hypochlorite (SH), a surfactant, and water is applied to the surface at low pressure. The SH oxidizes and kills algae, mold, mildew, and bacteria at the cellular level. The surfactant helps the solution cling to vertical surfaces and penetrate into pores so it can do its job before rinsing. Once the dwell time is complete, the surface is rinsed at low pressure. The result is a cleaner surface that stays clean longer because the organisms that caused the staining are dead, not just displaced.
Why pressure matters so much
Standard pressure washers operate at 2,000 to 4,000 PSI. That level of force is appropriate for concrete and some masonry. It is not appropriate for roof shingles, painted wood, or vinyl siding. High pressure on asphalt shingles blasts off the protective granule coating, shortening roof life significantly. On vinyl siding, it can force water behind panels and into wall cavities, creating moisture and mold problems inside the wall. Soft washing eliminates these risks by keeping pressure in the 100 to 500 PSI range, which is roughly the pressure of a garden hose.
Which surfaces require soft washing
Not every surface needs soft washing, but some surfaces should never receive high pressure. These include:
- Asphalt shingle roofs: High pressure removes granules and voids manufacturer warranties. ARMA (the Asphalt Roofing Manufacturers Association) specifically recommends soft washing.
- Vinyl siding: Soft wash removes algae and mildew without the risk of water intrusion behind panels.
- Painted wood siding: High pressure strips paint and raises wood grain.
- Stucco: Aggressive pressure can crack the surface layer.
- Older brick: Deteriorating mortar joints are vulnerable to high-pressure erosion.
For concrete driveways, sidewalks, and pool decks, higher pressure with a surface cleaner is appropriate and more effective.
The North Texas context
Fort Worth sits at 32 degrees north latitude with high UV intensity and humidity cycles driven by Gulf moisture. Those conditions create ideal growing conditions for Gloeocapsa magma, the cyanobacteria behind black roof streaks, as well as algae and mildew on north-facing siding. Soft washing is not just a preference here, it is the right tool for the climate. Properties that skip proper treatment and use only high-pressure rinsing often see regrowth within months because the organism is still alive in the surface pores.
What CARE uses
CARE's soft wash mix uses sodium hypochlorite, surfactant, and water. We do not disclose exact ratios, but the mix is calibrated by surface type and contamination level. Our roofs are cleaned at 100 to 300 PSI using a dedicated soft wash system. House washing runs at 500 to 1,200 PSI, well below the threshold for surface damage.
Learn more about house washing
For more on how we apply soft washing to your home's exterior, visit our house washing page or call (945) 275-8031.