Which roof moss treatment products prevent regrowth?
Short answer. The products that best prevent roof moss from coming back are zinc or copper strips near the ridge, periodic zinc powder treatments, slow acting spray and leave treatments, and, at replacement, algae resistant shingles with copper granules. Pair any of them with more sunlight and regular debris removal.
Long term treatment options
- Zinc strips: thin strips installed under the first course below the ridge with a small edge exposed. Rain carries zinc down the roof for years.
- Copper strips: work the same way and are more potent per area, but cost more and can tint runoff areas green.
- Zinc powder or granules: spread along the upper roof once or twice a year on shaded roofs.
- Spray and leave treatments: applied every year or two to keep growth from establishing.
- Algae resistant shingles: copper bearing granules built into the shingle; the most hands off option, chosen at replacement.
Choosing for your roof
- Roof under 10 years old, moss on one shaded slope: strips or annual powder.
- Whole roof prone to growth under heavy trees: strips plus tree trimming.
- Roof near the end of its life: skip big investments in treatment and plan for algae resistant shingles.
Installation notes for strips
Strips should be fastened under the shingle course so nail heads are covered, not face nailed through exposed shingles. Exposed nails become leak points. Effectiveness drops with distance below the strip, so long slopes may need a second row.
What no product replaces
- Trimming overhanging limbs; see trees and your roof.
- Clearing valleys and gutters of leaves and pine needles; see pine needles and leaves on the roof.
- Fixing drainage so water does not linger.
More background in moss and lichen on roofs.