Frequently Asked Questions

Soft washing works by applying a surfactant-and-oxidizer blend (typically sodium hypochlorite at 1–3% dilution with a biodegradable surfactant) directly to the surface. The oxidizer disrupts the cell walls of algae, moss, lichen, and mildew — killing the biology rather than just dislodging the visible growth.

High-pressure washing removes what you can see but leaves spores and root structures intact. Within weeks, those spores rehydrate and the growth returns — sometimes faster, because pressure washing can roughen surfaces and create better attachment points.

Because soft washing kills the root biology, results typically last 2–4× longer than pressure washing for organic staining. On shaded north-facing walls in the PNW, that can mean 12–18 months of clean surface before retreatment is needed.

All chemicals we use are rated biodegradable and we follow Washington State Department of Ecology runoff guidelines on every job. Plants and landscaping are pre-wetted and rinsed after treatment.

Most major asphalt shingle manufacturers (GAF, Owens Corning, CertainTeed) explicitly state in their warranty documentation that high-pressure washing voids the warranty. The granules embedded in asphalt shingles provide UV protection and fire resistance — pressure washing dislodges them, accelerating deterioration.

The Asphalt Roofing Manufacturers Association (ARMA) recommends low-pressure washing (below 1,200 PSI) with an appropriate biocide solution. Our roof wash process runs at 50–200 PSI — comparable to a garden hose — with a surfactant blend that dwells on the surface and kills moss at the root.

For cedar shake and metal roofing, pressure limits are even lower. We adjust chemistry and pressure based on the specific roofing material on your home. If you have a relatively new roof still under manufacturer warranty, ask us about our warranty-safe process documentation.

The other common mistake is using straight bleach without a surfactant. Bleach alone can streak and does not adhere to vertical surfaces long enough to work. A proper soft wash mix includes a surfactant that causes the solution to cling to the surface through the full dwell time.

The Pacific Northwest climate creates near-perfect conditions for biological growth on exterior surfaces. Average annual rainfall in Sammamish is around 44 inches, humidity stays elevated through the fall and winter, and extended overcast periods mean surfaces stay moist for weeks without drying fully between rain events.

Combined with the dense tree canopy common across the Eastside — fir, cedar, and maple create heavy organic debris and sustained shade — north- and west-facing surfaces almost never fully dry. These are ideal germination conditions for Gloeocapsa magma (the black algae that causes dark streaking on roofs) and Bryophyta (moss).

Homes in Klahanie, Pine Lake, and Beaver Lake areas of Sammamish — which have heavy fir canopy — tend to accumulate moss and algae significantly faster than open-exposure homes. Similarly, Issaquah Highlands homes above the fog line often have more sun exposure and slower growth cycles than homes in the valley.

We factor microclimate into our maintenance schedule recommendations. A heavily shaded home near a creek in North Bend has a different service cadence than a newer home on an open lot in Covington. After the first visit we can give you a specific recommendation based on what we observe.