gardening - how to remove roof moss

Asked April 2, 2017, 2:10 PM EDT

I am looking for an effective way to remove moss on a composition roof. I have tried bleach, Dawn Ultra, and have not been happy with the results. I just talked with Wilco. They recommend a 20 lb. bag of Moss Out, a granular product. I would appreciate any guidance you might have. This has been a very bad year for moss growth. Thank you for your assistance. Dave Stuntzner

Linn County Oregon

2 Responses

Thank you for your question about removing moss from your roof. Moss is quite common in the PNW, especially with the wet spring we have had. It is best to combine physical removal with a preventative.

First, physically remove the mosses with brushes and vigorous cleaning (please see Physical Control of Mosses on Roofs, Decks and Sidewalks). This can be dangerous if your roof is steep, so you might want to have the roof professionally cleaned - Pros have the equipment to do it safely. Once the surfaces are clean, there are a variety of products with varying degrees of environmental safety which can be applied to prevent the mosses from regrowing (please see Chemical Control of Mosses on Roofs, Decks, and Sidewalks). The least toxic seem to be potassium salts of fatty acids, like Safer; and properly diluted bleach. Bleach works, but plants must be protected and your roof would probably need retreatment every year or two. These products should be available in your local gardening center.

Here are a couple of articles on moss control that will give you additional information: Any Tips on how to safely remove my roof carpet? and Algae and Moss Prevention and Cleaning for Asphalt Roof Systems.

Care and Maintenance of Wood Shingle and Shake Roofs

Thank you. We are reading carefully and evaluating the information that you sent. We expect to follow the suggestions detailed in the information. Dave Stuntzner