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The Home Depot

Why Is My Roof Turning Green?

Pro Referral > Home Guides > Roofing > Why Is My Roof Turning Green?
Why Is My Roof Turning Green?

The roof is a major part of the external appearance of most homes and must be kept looking clean to enhance the appearance of the home. Additionally, the value of the property will be greater if the roof is clean, as it provides the impression of a well kempt home.


While a clean and well maintained roof makes a fabulous first impression, it also protects the structure from the elements. However, maintaining a roof properly can be difficult because it is exposed to extreme weather and is difficult to reach. Moss, algae, and lichen also grow well on roofs, as most roofs have moisture and debris of dead leaves to feed them. Additionally, if the roof has overhanging branches it provides the shade required for moss and algae to thrive.


When your roof is exposed to these conditions, you’ll notice it will actually start to turn green. This is certainly not what you want your roof to look like and you do not want your roof to become a living organism either.

  1. 1. Treatment

    If your roof is turning green it means that moss or algae has started spreading over the surface. In order to clean the roof you need to first kill the moss. Moss can be treated or killed by applying a solution of zinc sulfate to it. You can obtain zinc sulfate from home improvement stores or purchase commercial moss treatment solutions that contain zinc sulfate as the active ingredient. Apply the zinc sulfate solution evenly over the moss and leave it alone for four to six weeks. Depending on the heat, humidity, and other conditions, the zinc sulfate will kill the moss in this time. The moss will turn brown once it is dead.


    If you are in a hurry to kill the moss and clean the roof, you can also use a solution of commercial bleach on the surface. This will kill the moss between a few hours or a few days depending on the amount of growth present.

  3. 2. Cleaning

    Once the moss has turned brown, it needs to be removed from the roof. Dead moss can actually trap moisture underneath it and cause a fresh layer of growth to appear. The dead moss can be brushed away using a stiff brush or by hosing down the roof. If you are washing the roof, make sure that you only use a garden hose and not a power washer as the additional pressure can damage the shingles.


    Before washing the roof, cover the gutters with garbage bags so that the dead moss is washed down the sides of the roof to eliminate the chore of cleaning the gutters.

  5. 3. Prevention

    Once you have cleaned the roof of moss, you need to take steps to prevent the reappearance of moss and algae. Moss and algae do not grow in the presence of metal. So a periodic coating of zinc sulfate can slow down the growth of moss. Additionally, you can trim overhanging branches from above the roof to reduce shade and debris.


    Another way of ensuring that the roof receives a periodic metal wash is to insert copper or zinc strips at the top of the roof. Dissolved copper or zinc will continually cover the roof every time it rains, preventing further growth of moss even when the roof is moist. Preventative steps will help to save money in the future, as this growth will not occur again.

  7. 4. Roof Cleaning Services

    While it is possible for most people to clean the roof of their homes, time constraints, difficulty with climbing, and other problems can mean that you need to retain the services of a roofing contractor. Hiring a professional roof cleaner will ensure additional safety precautions are carried out, for they will have the necessary equipment and materials required to properly complete the job.


    A green roof detracts from the curb appeal of a house. However, if the homeowner is too busy to remove the moss from the roof and take preventative steps, they can retain the services of a roofing contractor using Pro Referral. A reliable roof cleaning contractor will clean the roof without damaging the shingles or the landscaping. This will ensure that your home maintains its attractive appearance without worry of further damage to your roof.

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