Does moss killer powder work on roof shingles?
How the powders work
Zinc compounds are toxic to moss and algae. Applied as a dry powder or granules, they dissolve with rain or dew and wash over the treated area. Dead moss turns brown and loosens over the following weeks, and rain or a soft brush then removes it. Zinc strips installed near the ridge work on the same principle, releasing zinc slowly over years.
Using it carefully
- Follow the label rate and directions exactly; it is a pesticide product.
- Apply from a ladder at the eave or with a long-handled spreader where possible, and avoid walking on a wet, mossy roof.
- Do not scrape or pressure wash moss off, which tears away granules and shingle edges.
- Protect plants, ponds and painted surfaces below from runoff.
- Check the label for warnings about staining concrete, stone and gutters.
Why moss grows in Georgia
Moss needs shade and moisture. North-facing slopes under hardwoods and pines, roofs where leaves and pine straw pile up, and areas below overflowing gutters stay damp long after rain. Moss holds water against shingles and can lift their edges, which leads to leaks and early wear.
Keep it from coming back
- Trim branches to let in sun and air.
- Keep debris off the roof and gutters flowing.
- On your next roof, choose shingles with copper-based algae protection, which targets algae and may slow other growth.
When to call a roofer
If moss has lifted or curled shingles, or the roof is near the end of its life, have it inspected before treating it. See moss and lichen on roofs and trees and your roof.