algae roof

How To Remove and Prevent Algae Stains on Your Roof

Ian Mutuli
Updated on
Ian Mutuli

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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Many people are proud of their home’s roof. But if there are algae stains covering it, they might be less than happy to show it off.

The good news is there are many ways to remove the algae stains from your roof and prevent them from coming back in the future. Read on to learn more!

What Is Roof Algae?

Algae is an organism that does not have leaves or flowers. Some people classify algae as a plant, and some leave it unclassified as a sort of "in-between" growth that isn’t a plant or an animal.

Algae can be green, brown, red, or yellow. Algae may also appear black due to the protective UV coating the microorganisms develop.

Algae often grow on roofs in warm, humid conditions. Algae alone generally do not damage your roof, but the stains do not look great. Algae grow well on asphalt shingles because they feed on the limestone filler.

Algae are also airborne, so there's no way to completely stop them from landing on your roof. The best way to handle algae is to remove it as soon as it appears. Algae can cover an entire roof in less than five years. If allowed to take hold, the algae will not be removable and require the installation of new shingles.

Algae begin as small spots and quickly grow to become black streaks or patches. Roofs regularly exposed to rain or snow are more likely to develop stains.

Algae stains can be a nuisance and an eyesore. Not only do they make your home look dirty, but they can also lead to further damage if left untreated.

What Causes Roof Algae?

Water is the leading cause of algae growth on roofs, either from humidity or standing water. If you keep your roof and gutters clean, you will reduce the chances of algae growth.

Algae stains are not only unsightly, but they can also be a sign of roof damage. It is important to keep your roof in excellent condition to prevent any costly repairs in the future.

How Does Roof Algae Cause Damage?

Algae growth is an indicator of moisture. Algae will not grow if the roof is too cold or if not enough water is present. Structural damage can necessitate major, expensive repairs if water is left long enough to get into the roof wood (even if no algae is present).

Because algae feed on the limestone in shingles, the shingle integrity may be affected if left long enough. Some shingles may come loose with time.

If you have enough dark algae covering your roof, it reduces the ability of the roof to reflect sunlight, which can increase the amount of heat circulating in your home. Breathing in algae, mold, and fungus can cause respiratory problems like asthma and allergies.

To be clear, algae is not mold. Mold is a type of fungus. Mold is slimier than algae and smells worse. Algae and fungus can work together to grow lichen. Lichen leads to moss. Birds may drop seeds on the moss, which leads to plant growth. The longer this process is allowed to occur, the more damage occurs.

How To Remove Roof Algae Stains

Climbing onto your roof to clean shingles is dangerous, plan your roof investment wisely and consider having a professional roofer perform this work and consider it a roof investment. If you want to do the scrubbing yourself, ensure you have the proper equipment (including a safety harness).

The first step to removing algae stains is to clean the roof with a particular detergent solution from a hardware store. You can do this by spraying the solution onto the roof or by using a scrub brush to apply it.

You can also remove algae with a mixture of bleach and water. You can buy a spray bottle and mix one part bleach with water. Allow the bleach to soak in for thirty minutes.

Mixing white vinegar and water will clean algae stains, but this less harsh method also takes longer to work.

Be sure to rinse the roof well afterward. Do not use a pressure washer because this can damage the shingles and cause leaks. Detergent and bleach can damage your roof shingles, so be sure to test them in an inconspicuous area first.

If growth has reached the point where you see moss, an ammonia and water spray will kill the plants.

One thing to consider is that harsh cleaners can damage your lawn and garden if they are allowed to drip off the roof. Remove excess liquid after cleaning.

How To Prevent Roof Algae Stains

It is better to prevent algae than to remove it. There is no way to stop spores from landing on your roof, but you can control them before they grow into algae. The goal is to make your roof an inhospitable environment for the spores to thrive.

There are a few things you can do to prevent algae stains from appearing on your roof in the first place. One of the best ways is to keep the roof clean and free of debris. Be sure to rinse the roof off with a hose to remove dirt.

You can also prevent algae from growing on your roof by ensuring your gutters are clear to let water drain properly. You should also check the roof for leaks.

If the shingles need replacing, you can buy some made with copper or zinc flakes. These metals kill algae. If you don't want to spend money on a new roof, you can place a copper strip under the row of shingles at the top. Rainwater will disperse the metal molecules and prevent algae growth.

You can also treat your roof with a sealant or algae inhibitor. These products help to prevent the growth of algae and other unwanted organisms. Increase the amount of sun hitting the roof by trimming trees and bushes close to the house. This sunlight will help dry out the roof and stop algae from growing.Keep your attic ventilated to reduce moisture levels. These are simple ways to make your rood less hospitable to algae.

It is essential to deal with algae as soon as you see it, either independently or by contacting a professional. Algae stains can be a nuisance and an eyesore on your roof. Not only do they make your home look dirty, but they can lead to further damage if left untreated.

What Are Alternatives to Asphalt Shingles?

Because algae feed on the limestone in asphalt shingles, one way to prevent stains is to choose a different roofing material.

There are a few alternatives to asphalt roof shingles:

Metal roofing is a good option because it is very durable and can last for 50 years. Metal roofing is also a good option for homes in hurricane-prone areas, as it is resistant to wind and hail damage.

Tile roofing is resistant to weathering, fire, and insects.

Slate roofing is the most durable type, but it is also the most expensive.

If you are looking for a more affordable alternative to asphalt roof shingles, then you may want to consider synthetic roofing. Synthetic roofing is plastic and very durable. You can install it quickly and easily. However, synthetic roofing is not always considered as aesthetically pleasing as other roofing materials.

Steel roofing is becoming popular as a green building material because it is one hundred percent recycled. It is also energy efficient, which can help reduce your energy bills.

Wood shingles have a great aesthetic and are popular among homeowners. However, they are not as durable as other roofing materials and require more maintenance than others.

Slate shingles cost more than other roofing materials, but they can last for up to 100 years. They are also very resistant to weathering, fire, and insects.

Rubber shingles are a green option made of recycled materials. They are also strong and can last for up to twenty-five years. Rubber is a low-cost option that requires very little maintenance.

Plastic composite shingles are another low-cost option composed of recycled materials. These shingles are available in many colors and shapes. They are also durable and remain in good condition up to thirty years.

No matter what type of roofing material you choose, be sure to have a qualified roofing contractor install it. A good roofing contractor will recommend the best roofing material for your home and ensure a quality installation.


There are many quality roofing materials to choose from, so be sure to research your options before deciding. The best material for your home will depend on your budget, climate, and lifestyle. But it’s important to take your likelihood of attracting algae as a factor.

Moss and mold can be a nuisance on your roof. Not only are they unsightly, but they can also cause damage over time. In this article, we've outlined how to remove these stains and prevent them from forming in the first place. Follow these tips, and you'll be able to keep your roof looking its best for years to come!

Ian Mutuli

About the author

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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