Roof Algae

I have a northern exposure to the front of my house. It does not get direct sun. I live in Sussex County, DE. mid-Atlantic area. I have black streaks and a slight green color (moss?). I recall you talking about running a strip of copper under the top ridge and the rain causes a chemical reaction to help with this problem. Could you please explain this again, how much copper to expose, how is it to be secured, and should I do something to the roof beforehand (power wash with bleach) or will this take care of the problem?

Thank you in advance. I looked through the archives but could not find my answer. Great show and web site.


A zinc or copper strip that it attached to the roof just below the hip and/or ridge can be found in the roofing section of most hardware stores or home centers. The product can also be found at most roofing supply companies.