How to Prevent and Remove Moss on Shingles

Q: In recent years, moss and lichen growth on asphalt roof shingles seems to have become an increasing problem in our area. What’s the best way to prevent recurring organic growth on roofs and, when preventative measures fail, what’s the best way to remove the growth?

A: Mike Guertin, a builder and remodeler in East Greenwich, Rhode Island, and frequent presenter at JLC Live, responds to the Journal of Light Construction: I have spent a fair amount of time dealing with moss, lichens and algae on roofs. It’s a problem here in Rhode Island, especially at my own house, and it doesn’t seem to be limited to a particular type of asphalt shingle. Laminated shingles may have more nooks and crannies where debris can settle and provide food for moss, and the edges may make it easier for spores to hang tight until they begin growing, but I don’t know of any studies on whether three-tab or no-cutout single-tab shingles are less prone to organic growth than architectural shingles.

Prevention

As far as I know, there aren’t any “moss-resistant” shingles, though there are algae-resistant ones made with granules that contain copper, such as Owens Corning’s StreakGuard shingles. When it rains, copper ions wash out of the granules to inhibit algae growth. To help resist moss growth on a new roof, you can install copper or zinc strips according to the manufacturer’s instructions.

Related:How to Restore a Slate Roof

To read the rest of Guertin's response to JLC, click here.