Q: Could you advise how to deal with moss on a home’s roof shingles?

A: Walk through your neighborhood and observe the roofs. Notice that the shingles below a roof-penetrating vent pipe are often a different color from the rest of the roof. The light color is caused by lead salts which slowly dissolve from the lead flashing around the vent pipe. You’ll never see any moss growing in an area where metal salts are present.

Copper, zinc and iron compounds also kill moss. One option is to hire a handyperson to stretch 10 gauge copper wires horizontally from one end to the opposite end of the roof. Start at the ridge – one wire will be stretched parallel on one side of the ridge, the other will be on the second side of the ridge. Go down ten feet from the ridge peak and stretch another wire across if possible. The slowly dissolving copper kills moss but does not harm plants under the eave of the house. Moss Out! Roof Strips(tm) uses zinc strips nailed below the roof ridge.

You can also kill roof moss temporarily by spraying it with a solution of ferrous ammonium sulphate (Moss Out(tm)), algicidal soap (Schultz Moss And Algae Killer(tm)) or copper sulfate.