Moss & Organic Growth Treatment

Oregon's climate is perfect for organic growth — wet fall through spring, then warm summers. North-facing walls and shaded areas stay damp longer and grow moss faster. Soft washing kills the growth at the root level and leaves a residual effect that keeps surfaces cleaner for 18-24 months.

We use sodium hypochlorite-based solutions (similar to pool shock) mixed with surfactants. These break down into salt and water after application and won't harm plants if we pre-wet and rinse landscaping properly. The chemicals do the work — we apply them at low pressure and let them dwell for 10-15 minutes before rinsing.

“Oregon's climate is perfect for organic growth — wet fall through spring, then warm summers. North-facing walls and shaded areas stay damp longer and grow moss faster.”

Roofs are the most common application. Moss holds moisture against shingles and shortens roof life. Soft washing removes the moss without the shingle damage that pressure washing causes. We apply solution from the ground or from ladders at the roof edge, let it dwell, then rinse. The moss dies within a few days and weathers off naturally over the next few weeks.

Siding, fences, and decks get the same treatment but with adjusted chemical concentrations. Heavy moss may require a second application or some manual scraping before treatment. The residual effect prevents regrowth for 18-24 months, which is 2-3 times longer than pressure washing alone.

AWP Exterior Cleaning handles moss and organic growth treatment across Oregon and Western Washington. Properties in both states deal with similar climate challenges — constant moisture, shaded areas, and north-facing walls that stay damp. Coastal properties in Western Washington see heavier moss growth from higher humidity, while valley properties in Oregon deal with more tree cover that creates shaded areas.

Typical moss treatment costs $300-$600 for whole-house application depending on square footage and growth severity. Roof-only treatment is $400-$800 for most single-family homes. Results last 18-24 months, so many customers move to a two-year treatment cycle after the first application. If you're seeing green or black growth on your roof or siding, the moss is already established and needs treatment.