The Importance of Roof Cleaning

Keeping your roof clean is essential to maintain its lifespan. It also protects the interior of your home from mold and fungus, and it helps prevent pest infestation.

First, hose down the roof to loosen dirt and grime. Be sure to protect surrounding plants, garden beds and trees since runoff from bleach solutions or cleaning chemicals can damage them. Contact Sarasota Roof Cleaning now!

Often mistaken for mildew or mold, roof algae is actually a type of bacteria. These organisms grow on the surface of your roof as a result of moisture buildup and lack of sunlight. Depending on the specific organism, algae can take many forms. Generally, they have a black-green hue and can be found on wood or asphalt shingles as well as concrete tiles. The most common form of roof algae is Gloeocapsa magma, a type of bacterium that eats water and expelses oxygen, leaving behind the dark streaks you see on your roof.

Algae can be difficult to get rid of on your own. You may be tempted to use household bleach or a pressure washer on the problem areas, but this is not recommended. The harsh chemicals and high-pressure streams of water can actually damage or shorten the life of your shingles. Plus, the pressurized water can cause leaks under your tiles and past the underlayment, or carve divots into your roof sheathing.

The best way to get rid of roof algae is to hire a professional. A licensed roofing contractor knows how to clean the stains without damaging your roof and will recommend ways to prevent future growth, such as special roof coatings or gutter replacement. They can also trim nearby trees to reduce shade and moisture levels, which will make it harder for moss and algae to thrive on your roof.

While algae stains are not harmful to your roof, they do lower the curb appeal of your home and can hide the original color of your shingles. Algae stains can be removed with a solution of trisodium phosphate (TSP), bleach, and water. You should spray the solution on your roof and allow it to sit for 30 minutes. Then, rinse with a garden hose. Repeat if necessary, and rinse again afterward to ensure that all the staining is gone.

Algae spores can travel on the wind to other structures on your property, such as sheds and barns. If these structures are not cleaned immediately, they will grow similar streaks of algae. These organisms are not just unsightly, but they can also be a health hazard to your family.


Dirt that is left unattended can clog gutters, leading to water damage to the roof and your home. This can be very expensive to fix and also leads to other problems like moss, algae, and mold. A simple clean-up with a hose can remove most dirt. But if the accumulated dirt has caused the buildup of moss, algae or mold it is best to use an algaecide or fungicide on the roof. This will not only clear the spores but will prevent them from returning.

Moss and algae are more than just unsightly, they hold moisture that can degrade shingles and cause leaks into the home. These plants also grow their roots into the shingle surface and cause the shingles to lift up and break. A roof cleaning will remove these spores and the root system of the plants to prevent them from growing back.

The most common way to clean a roof is with a power washer, but this is not ideal for every roof. This can damage the shingles and also the protective coating on metal roofs. It is best to use a hose with low pressure, and this method works well on most homes.

Before applying any cleaner to the roof:

  1. Sweep or blow off loose debris. This will help prevent slips or trips and allow the cleaning solution to reach the stains more effectively.
  2. Start at the top of the roof and work your way down.
  3. After spraying the cleaner, allow it to dwell for 20 minutes.

During this time you should wear protective clothing, including gloves and eye protection, and make sure the surrounding flower, trees, bushes, and grass are protected from any runoff or spillage.

Some homeowners prefer to use bleach to kill the stains on their roof. This requires a pump sprayer or backpack sprayer that has been properly sized to avoid leaking. A 50/50 mixture of liquid chlorine bleach and water is sprayed on the stains and allowed to soak for about 20 minutes. Then, a rinse of low-pressure water is applied to thoroughly rinse away any remaining cleaning solution and the dead moss, algae or fungus.


Moss may look charming on a cottage roof, but it damages asphalt shingles and other roofing materials over time. It widens fissures and gaps in the shingles, as well as pulls moisture from gutters and downspouts toward the foundation of your house. If the moss is allowed to remain on your roof, it will eventually cause the underlayment and decking to deteriorate, leading to roof collapse and serious water damage.

A power-washer can be used to remove moss from the roof, but it should be done at the lowest setting to avoid damaging shingles and stripping them of their protective granules. Alternatively, a long-handled soft-bristle scrub brush can be used to brush the moss off of the roof, starting at the eave line and working upward. Work in one section at a time to prevent lifting shingles and to avoid creating a tripping hazard.

If a physical removal with water and brush doesn’t remove all of the moss, a commercial or DIY cleaning solution can be applied to kill the remaining spores. Follow the manufacturer’s instructions on the product you choose. Most moss killers need to be applied when rain is forecast, as they depend on rainfall to activate and distribute them. Before you apply any moss killer, wear rubber gloves and goggles to protect yourself against the chemical as well as the spores.

You can purchase a variety of commercial moss-killing cleaners, including specialized roof cleaning products such as Spray & Forget. Some of these are designed to clean as they kill, while others require you to manually scrub the moss off with a brush before you rinse and dry. If you use a commercial product, read the label carefully to determine how long the product should be left on the moss before rinsing it off of your roof.

If you prefer to use a homemade cleaner, you can mix bleach or chlorine bleach with water in a spray bottle to create your own cleaner. Make sure to follow the manufacturer’s directions on how much bleach and how much water to use. Both of these cleaning options can damage plants under your roof, so be sure to spread plastic sheeting or cover any vegetation with a tarp before you begin.


Mold is a type of fungus that, like algae and moss, grows on organic materials. It is a natural recycler of dead organisms and helps decompose organic material in the environment. However, it can be a nuisance when it grows on a roof and may cause damage to the shingles.

A common way to get rid of mold is to kill it with a bleach solution. However, this method can be messy and is not recommended for use on a roof. Bleach is also toxic to plants and can corrode some building materials. A better option is to use a fungicide that is safe for all surfaces and is easy to apply. Several products are available, such as Wet and Forget, which can be purchased in a hose-end sprayer, concentrate or ready-to-use formula.

To kill the mold:

  1. Prepare a solution of 1 quart bleach, 1 gallon water and 1/4 cup trisodium phosphate (to help remove staining).
  2. Mix well and then pour into a pump sprayer.
  3. Apply the solution to the affected areas, starting at the bottom of the roof and working upwards.
  4. Spray generously, but do not oversaturate the shingles or allow the solution to soak for longer than 20 minutes.
  5. After spraying, rinse the shingles thoroughly with a garden hose at low pressure to remove any remaining bleach solution.

Be sure to wear rubber gloves, goggles and a breathing mask to protect yourself from the chemicals. Cover any vegetation that is near the affected area with tarps or plastic sheets to prevent damage from cleaning solution runoff. It is also important to practice proper roof and ladder safety, including wearing a harness if needed for steep or difficult-to-climb areas of the roof.

Once the mold is killed, re-seal the shingles with a waterproofing roof sealant to prevent future problems. This is a vital step because the deteriorating shingles will provide an ideal substrate for additional mold and mildew growth. In addition, a sealed roof will help to prevent moisture from entering the house and damaging the wood studs and insulation. In addition to protecting the shingle surface, a quality roof sealant will also increase the life of the shingles and help them perform more efficiently.