Removing algae and moss from your roof


When living in a humid area, it’s possible your roof is covered with moss, algae or lichens. They can grow on every type of roofing material: bitumen shingles, concrete and/or ceramic tiles, slates or even painted metal sheets.


Moss on bitumen roof shingles, concrete tiles, ceramic tiles and painted metal sheets. >>>

Unfortunately the stains these organisms leave on bitumen roof shingles make your house look terrible and sometimes desolate, which reduces the value of your house. In some cases, these stains are a rather cosmetic issue. But in some cases these stains are symptoms of something much worse. It can lead to serious damage or even roof failure. Sometimes it can be easy to find the causes of the stains, and even to get rid of them and prevent them from recurring.


Common causes of staining

Dark stains on a bitumen shingles roof could be caused by different causes:

2.      Moss

Velvety green masses of moss often grow on the north-facing side of roof surfaces and on tree-shaded roofs. Unlike the above mentioned algae, leaving moss on your roof surfaces can develop bigger problems. By infiltrating the roof structure underneath the shingles, moss can make the shingle edges lift and curl. This can lead to cracking and blow-off during high winds and storms. Another effect of heavy moss growth is the forming of dams which can cause water to back up underneath the roof shingles and damage the roof deck. Best thing to do is clean off moss as soon as you notice it on your roof!

Moss on shingles roof >>>

DIY Algae and moss removal recipes

Luckily both algae and moss can be easily removed from shingle roofs. DIY stores sell many popular liquid solutions that are specifically made to kill the moss. Or you can make your own moss remover in a large spray bottle with one of these four DIY recipes:

  • • 240 ml dish washing soap + 7,5 liter of water
  • • 450 grams powdered oxygen bleach + 7,5 liter of water
  • • 500 ml chlorine bleach + 7,5 liter of water
  • • 500 ml white distilled vinegar + 7,5 liter of water

When using one of these homemade options, you should wet down the roof with plain water first, then apply the cleanser and let it rest for 20 to 45 minutes. Lightly scrub your roof with a soft-bristle brush, and then rinse with water.

If accumulations of algae or moss are heavy, a part of it should wash off the roof surface immediately with the stream from the garden hose. Using a brush or broom with medium-stiff bristles you can attempt brushing off algae and moss, but don't scrub too hard. You don't want to brush off the mineral granules from the shingles.

If algae, moss or heavy stains persist on your roof surface after rinsing, let the roof dry, and then spray on the bleach solution again. Again wait for 30 minutes and rinse with a hose. Don't worry if some staining remains after this second rinse. Exposure to rain and sunlight should wash it off over time.

Following these maintenance tips can help you enjoy your attractive roof. They can also help extend your roof’s service life, which is important whether you plan to stay in your home or sell it in the future.

More tips on the protection of your roof can be found in our blogs.

Good luck!