How To Clean And Prevent Algae And Moss Growth On Your Roof

10 February 2016
 Categories: Construction & Contractors, Articles


You want your shingles and roof to last as long as possible, so it is important to take care of your home's roof and shingles by cleaning and removing any moss and algae growth. Here are tips to help you clean them and how to prevent future algae and moss growth problems.

Moss Removal

Northern-facing roofs and roofs that are in the shadow of any large yard trees tend to stay wet for longer periods. Moisture on a roof can promote the growth of moss between shingles. The moss growth can build up and block the natural drainage on your roof, causing roof leaks and damage to other roofing materials. Moss roots can also trap moisture in the shingles, causing wood rot and erosion of your shingles.

To remove the moss, you will need a bristled scrub brush with a long handle. Starting at the top of your roof, brush the bristles down the shingles to dislodge the moss from them. Be careful not to brush upward because this can lift and break your shingles. Continue this any time you see new moss growth on your roof.

Algae Removal

Moisture for prolonged periods on your roof shingles can also cause algae growth. Algae spores in the air land on your wet shingles and grow and form algae colonies. These colonies will present themselves as dark stained patches and streaks down your roof. 

Algae growing on your roof makes your roof look ugly and can damage your shingles as it feeds on the limestone particles in composite shingles and grows larger. Over time, this feeding will break down the materials in your shingles, causing them to crack, peel, and lift, requiring replacement. For this reason, it is important to clean off any algae growing on your roof shingles. 

If your roof shingles have been treated with an algicide to prevent algae growth, it will eventually wear off and algae will begin to grow there. Don't use a power washer to clean your roof because the force of the water spray will dislodge the particles of your shingles and damage them. It is best to use an oxygen bleach cleaning solution or a roof cleaning product sold at most home improvement stores, and you can apply it with a pump sprayer and nozzle.

Plan to clean your roof with either product on an overcast day so your roof is not hot from direct sunshine. First, spray down your roof with your garden hose to cool the roof. If your roof is hot when you apply the cleaner, it will cause the cleaner to evaporate before it has a chance to clean the algae from its surface. 

Mix your roof cleaning product according to the manufacturer's directions and pour it into your pump sprayer. If you are making your own bleach solution, combine one quart of six percent sodium hypochlorite bleach with one gallon of water. Then, add 1/4 cup of trisodium phosphate and put it in your pump sprayer.

Spray the solution over your roof, starting at the bottom of your roof and working your way up. Be sure to saturate each section of shingles until you see runoff of the solution. Allow the solution to sit for at least 15 minutes, then use a sprayer nozzle attached to your garden hose to rinse it off. 


Once you have removed the moss and algae from your roof, you can add a copper strip of metal to the ridge of your roof. Copper has properties that prevent the growth of algae and moss. As moisture runs down your roof, trace amounts of the copper will run down with the moisture and prevent growth on your roof. You can find strips of copper at roofing supply stores to install on your roof. 

Another option to prevent regrowth of moss and algae is to spray a stain blocking solution to your roof for prevention growth that can last up to three years. You can find this solution at most home improvement stores.

Then, if it is time to replace your roof shingles, you can choose replacement shingles containing granules of copper to prevent algae and moss growth.

Use these tips to help keep your roof free of moss and algae growth. For more tips or to have your roof inspected for damage caused by moss and algae, contact a company like Miller Roofing & Guttering Inc.