While black stains on roofs are a cosmetic issue, moss growth is more than just cosmetic. Not only does moss look terrible on roofs, it will also shorten the life of the roof covering and possibly lead to roof leaks. Whether you have wood or asphalt shingles, moss can grow on the roof if it doesn't dry properly.
In this video, This Old House general contractor Tom Silva shares tips for keeping a roof free of moss and mold. You can cut strips of zinc flashing copper and lead work, too and slide them under a course of roof shingles to kill lichen and moss growing there, or you could just buy these premade strips from Shingle Shield. The premade ones are much quicker and probably neater looking.
Zinc Strips kill moss. The moss dies and the roof stays moss free for 10 feet under a zinc strip for five years or so if it stays in place and stays flat. Homeowners can install strips of zinc, purchased at a hardware store.
A zinc strip can be installed on a roof to prevent moss from growing. The zinc prevents the growth of the moss as the strips become corroded from moisture. The corrosion releases the zinc.
For decades, zinc strips have been used to keep moss from growing on roofs. This is an explanation of how they work and how they are installed. It also explains the limitations of zinc strip, from the point of view of good roofing practices and experience.
I have heard this bandied about between roof cleaning companies and home inspectors and roofers. The fact is: it Does work. Zinc strips on your roof keep it looking new.
Angie's List Answers is the trusted spot to ask home improvement and health questions and get answers from service companies, health providers and consumers. For ratings and reviews on companies in your area, search Angie's List. Absolutely - you can easily do yourself if you are not afraid of roofs - just be sure to tuck the nails up under the edge of the top row of shingles not the ridge shingles - they break too easy, though fine to put there during a reroofand hit the nail heads with a dab of bitumastic roof caulk to ensure they don't leak. Also, be sure to get it far enough up the shingles tht the nails do not cut through the edge, because it tears easily in strong winds if thereis a starting nick in the edge.
I had zinc strips applied to my roof and they do keep the moss at bay. They were slid under the edge of shingles, but were nailed in. Not sure about caulking them in.