If you’ve been researching roof cleaning, you’ve probably come across the term “soft wash.” It gets thrown around a lot, but not always with a clear explanation of what it actually means or why it matters for your home. Here’s a straightforward breakdown of the soft wash process, why it’s the recommended method for most roofs, and what to expect when you have it done.
How Soft Washing Works
Soft washing is a cleaning method that uses low water pressure combined with a specialized cleaning solution to remove biological growth from roof surfaces. We’re talking about algae, moss, lichen, mold, and mildew, all of which thrive in the wet Pacific Northwest climate.
The pressure used is typically no more than what comes out of a standard garden hose. The cleaning power comes from the chemistry, not the force. The solution kills and breaks down organic material at the cellular level, and a gentle rinse washes it away.
This is the key difference between soft washing and pressure washing. Pressure washing relies on brute force. Soft washing relies on science.
At Hydra Clean, our RooxRX™ soft wash treatment is formulated specifically for the types of growth common on roofs in Washington State, from the heavy moss buildup in Whatcom County to the algae streaking that shows up across the Eastside and South Snohomish County.
Why Pressure Washing Is Bad for Your Roof
Asphalt shingles, the most common roofing material in North America, have a protective coating of granules embedded in the surface. These granules shield the underlying asphalt from UV radiation and provide fire and weather resistance.
High-pressure water physically strips these granules off. Even moderate pressure washing can remove years of protective coating in a single cleaning session. This accelerates shingle degradation, voids most manufacturer warranties, and can lead to premature roof replacement.
Metal roofs are more forgiving with pressure, but even on metal, high pressure at close range can damage coatings, loosen fasteners, and force water under overlapping panels. We cover metal roof specifics in our post on how to clean a metal roof.
What Does the Soft Wash Solution Contain?
Most soft wash solutions are based on a diluted sodium hypochlorite solution combined with a surfactant. The surfactant is essentially a detergent that helps the solution cling to the roof surface and penetrate organic growth instead of running off.
The solution is applied at low pressure, allowed to dwell on the surface for 15 to 30 minutes, and then rinsed off. During that dwell time, the active ingredients kill algae, moss, lichen, and other biological material at the root, rather than just scraping it off the surface.
Because the growth is killed rather than just dislodged, soft washing produces longer-lasting results than mechanical cleaning. You’re treating the problem, not just removing the symptoms.
Our RooxRX™ formulation uses eco-friendly, biodegradable ingredients that are safe for your landscaping, pets, and the local watershed. That matters in a region where we all live close to Puget Sound and rely on clean water.
What Problems Does Soft Washing Fix?
Soft washing is effective against the most common types of roof growth:
- Algae (Gloeocapsa magma): the primary cause of those dark black streaks running down your roof
- Moss: green, textured growth that holds moisture against your shingles and accelerates decay
- Lichen: a stubborn algae-fungus combination that bonds tightly to shingle surfaces
- Mold and mildew: typically found in shaded, humid areas under tree canopy
In the Pacific Northwest, moss is the biggest offender. Homeowners from Bellingham to Seattle deal with it year-round thanks to our mild, wet winters. But black algae streaks are nearly as common, especially on lighter-colored roofs in sunnier spots.
For more on these specific problems, see our guides on what causes black streaks on roof shingles and how to clean moss off a roof.
What to Expect During a Professional Soft Wash
Here’s the typical sequence when our crew arrives:
- Pre-inspection: We assess the type and extent of growth, check for damaged shingles, and identify the best access points. We often use drone cameras for a full roof survey before anyone steps on a ladder.
- Preparation: Landscaping around the house is pre-wetted to protect plants from overspray.
- Solution application: The RooxRX™ cleaning mixture is applied at low pressure, often from the gutter line or ground level.
- Dwell time: The solution sits on the surface and does its work for 15 to 30 minutes.
- Rinse: A gentle low-pressure rinse removes the dead biological material.
- Post-cleaning check: The roof is inspected for any remaining growth or shingles that need attention.
After a soft wash, you may notice some residual discoloration, especially where growth was heaviest. Over the following weeks, rain helps wash away the last of the dead material, and the roof continues to look cleaner over time. That’s normal and expected.
How Long Do Soft Wash Results Last?
Under typical conditions, results last between one and three years depending on tree cover, shade, and local microclimate. Homes tucked under heavy canopy in areas like Woodinville or Issaquah will see regrowth sooner than homes in more open areas.
For homeowners who want to stay ahead of regrowth without worrying about scheduling, our HomeShield maintenance plans include regular roof treatments on a schedule that keeps moss and algae from ever getting a foothold again.
Is Soft Washing Safe for All Roof Types?
Soft washing is the recommended method for asphalt shingles and is also safe for tile, cedar shake, slate, and composite roofing. For metal roofs, the approach is adjusted slightly with different solution concentrations and dwell times suited to the material.
The important thing is working with a crew that understands your specific roof type. A cedar shake roof in Redmond needs a different touch than a composition roof in Lynnwood. One-size-fits-all doesn’t work with roof cleaning.
Where We Provide Soft Wash Roof Cleaning in Washington
We clean roofs across the Pacific Northwest. In Whatcom and Skagit Counties, we serve homeowners in Bellingham, Lynden, Ferndale, Mount Vernon, and Anacortes. On the Eastside, we cover Redmond, Bellevue, Kirkland, Sammamish, and Mercer Island. And from our home base, we handle Lynnwood, Mill Creek, Bothell, Edmonds, Everett, and the surrounding communities.
Wherever you are, the moss is the same, and the solution is the same: a professional soft wash that protects your roof instead of damaging it.
Ready to Clean Your Roof the Right Way?
If your roof has moss, black streaks, or just looks like it’s been neglected for a few seasons, a soft wash is the safest and most effective way to restore it. We offer free drone inspections so you can see exactly what’s up there before we start, and every job is backed by our 100% satisfaction guarantee and $1M liability insurance.
Get a free roof cleaning quote or call us to schedule your RooxRX™ soft wash treatment.