Roof Moss Treatment
Roof moss treatment is killing moss on a roof with a gentle biocide or soft wash solution and letting rain and wind clear it away, instead of scraping or pressure washing it off. Moss holds moisture against shingles and lifts their edges, but aggressive removal strips granules and does more harm than the moss.
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In depth
Moss prefers shaded, north-facing slopes where shingles stay damp, especially under trees. Treatment is applied from the ground or a ladder and left to dwell, and the moss dies and releases over the following weeks. Brushing dead moss lightly or letting rain remove it is safer than scraping. Zinc or copper strips along the ridge slow regrowth. Trimming overhanging branches so sun and wind dry the roof is the long-term fix. A roofer should repair any shingles that have already lifted.
How this shows up on our jobs
Shaded Madison roofs under mature oaks and maples stay damp through spring, which is moss weather. We treat moss and lichen with soft wash only, never pressure.
Services where this matters
Frequently asked
- What is Roof Moss Treatment?
- Roof moss treatment is killing moss on a roof with a gentle biocide or soft wash solution and letting rain and wind clear it away, instead of scraping or pressure washing it off. Moss holds moisture against shingles and lifts their edges, but aggressive removal strips granules and does more harm than the moss.
- How does Roof Moss Treatment show up on our jobs?
- Shaded Madison roofs under mature oaks and maples stay damp through spring, which is moss weather. We treat moss and lichen with soft wash only, never pressure.
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Related terms
Moss vs. Lichen
Moss and lichen are both organisms that colonize roofs and exterior surfaces in Wisconsin, but they are biologically distinct and require different removal strategies. Moss is a non-vascular plant that holds moisture against the surface — on a shingle roof, trapped moisture under a moss mat accelerates granule loss, lifts shingles, and leads to freeze-thaw damage at the mat's edges. Moss is soft, green, and responds well to sodium hypochlorite soft washing plus a zinc-strip regrowth inhibitor.
Gloeocapsa Magma
Gloeocapsa magma is a photosynthetic cyanobacteria that feeds on the limestone calcium carbonate filler embedded in asphalt shingles. It is the organism responsible for the black or dark-gray streaks that run from ridge to eave on millions of American roofs. Algae spores are carried by wind, birds, and squirrels, which is why you'll often see streaks appearing on one slope of a roof before the other, and why entire neighborhoods in Madison begin showing streaks within a few years of each other once the spore population establishes locally.
Zinc Strip
A zinc strip is a 6-inch-wide roll of thin galvanized metal installed along the ridge cap of a roof to provide long-term, passive algae and moss suppression. When it rains, water washes over the zinc and picks up trace zinc ions, which then flow down the shingles and create a biostatic environment that prevents algae, moss, and lichen from establishing colonies. A single properly installed zinc strip at the peak can keep an asphalt shingle roof clean for 10-15 years with no further treatment.
Soft Wash
Soft washing is a low-pressure exterior cleaning method that uses biodegradable detergents and a controlled bleach solution to kill the algae, mold, mildew, and bacteria that cause staining — rather than scouring them off with brute force. A soft wash rig delivers cleaning fluid at roughly 60-200 PSI, comparable to a strong garden hose, which is safe on siding, shingles, painted surfaces, screens, and caulking. The chemistry does the work: the solution dwells on the surface, breaks down the organic growth at the cell level, and is then rinsed clean with fresh water.
Biocide
A biocide is any chemical agent that kills living organisms — bacteria, fungi, algae, mold, mildew, lichen. In exterior cleaning, the most common biocides are sodium hypochlorite (bleach), quaternary ammonium compounds ("quats"), and hydrogen peroxide. Each has a place: sodium hypochlorite is the fastest and most cost-effective broad-spectrum kill; quats provide residual antimicrobial action that slows regrowth on treated surfaces; peroxide is the mildest and is used where chlorine would damage the substrate.
Asphalt Shingle Granule Loss
Asphalt shingle granule loss is the shedding of the small mineral granules that coat the top of asphalt shingles and shield the asphalt from sunlight. Some loss is normal with age, but heavy loss, bare dark patches, and granules piling up in gutters signal a roof that is wearing out and exposed to UV damage.