What Is Roof Cleaning and Why Is It Necessary?

Roof Cleaning Charleston SC is the process of removing algae, mildew, moss and lichen spots from a home’s roof. It also reveals areas that are damaged or in need of repair.

Chemical solutions are usually used to treat and kill stains on a roof. They can be applied either by hand or with a sprayer.

Storms, high winds, and even the growth of moss on a roof can result in debris build-up. This material can damage shingles or tiles, making them more vulnerable to breakage in high wind and also leaving them susceptible to moisture penetration and damage to the substrate or attic of your home. Small pieces of debris can also clog gutters and cause wet spots on interior walls. The best way to protect your roof is to make sure you are routinely removing debris. This can be done by sweeping or using a leaf blower, particularly after a wind storm. It is also a good idea to trim any trees that hang over your roof to ensure they are not creating excess shade and dropping leaves or other materials on the surface of your roof.

When you do decide to remove debris, it is important that you do so in a manner that does not damage the roof or the ladder. Always use a ladder that is in good condition, and avoid walking on the roof itself unless you are completely comfortable doing so. Debris can be quite heavy, and fighting with it while trying to maintain traction on the ladder is dangerous, especially if the weather is bad.

Once you are ready to begin cleaning, you will want to start with the lightest materials first. A broom or leaf blower can quickly remove light debris such as pine needles or dry leaves. For the heavier items, a ladder with a tarp can be placed under the item, and then it can be blown or lifted away. This method allows you to save time and energy while avoiding the potential for damage.

Depending on the type of roofing material, there may be additional steps that need to be taken to clean it. A specialized cleaning agent is used to gently clean asphalt shingles, for instance, while cleaning cedar shakes may require a mixture of water and detergent or bleach.

When the cleaner is applied and has had a chance to work, it should be rinsed off with a garden hose. The rinsing is meant to rinse the cleaning solution as well as any loosened grime or dirt. Once the roof is fully rinsed, check to make sure the gutters and downspouts are free of clogs, and then recheck your roofing materials for any signs of damage or wear.

Algae Removal

Algae is the dark discoloration and streaks you may notice on many roofs, especially those near coastlines or in humid climates. Algae thrive on the perpetual moisture that dwells on roof surfaces, and can quickly spread and eat through roofing materials if not removed. Left unattended algae will shorten the lifespan of your shingles and can lead to roof leaks, rot and mold problems.

The Asphalt Roofing Manufacturers Association (ARMA) recommends using a bleach-and-water solution to kill and remove algae. This consists of a 50 percent mixture of laundry strength liquid chlorine bleach and water that is applied to the surface of the roof with a sprayer or garden hose. The mixture should be allowed to dwell on the surface for 15 to 20 minutes, and then rinsed thoroughly with low pressure water. When working with chlorine bleach, always take proper safety precautions to protect yourself and others. Also, be sure to wet foundation plantings that receive run-off from the roof with clean water before you start spraying the bleach solution on them.

While bleach is effective in killing and removing the algae, it does not rinse away completely. ARMA advises rinsing with clean water after the bleach wash to fully remove the remaining debris and prevent the growth of new algae. You can speed up the rinsing process by blowing water downward on the roof, but be careful not to get the water under the shingles.

A more permanent solution for curbing algae is to install strips of copper or zinc on the roof, just below the chimney area. These metals are toxic to algae, and when it rains the copper or zinc washes down the roof, killing any existing algae and keeping it from regrowing.

Moss is harder to get rid of, but a thorough cleaning with a special moss removal product is helpful. You can try spraying the roof with a fungicide, or you can use a small, semi-stiff brush to loosen and then rake the moss away. The best time of year to do this is when the roof has rained recently but not yet dried.

Chemical Treatment

When it comes to removing moss, lichen, mildew and other organisms that can damage a roof over time, chemical treatment is the best option. This method uses specific chemicals such as a low concentration of chlorine bleach, sodium percarbonate or copper sulfate to kill and remove the organisms from the roof surface. Usually, these chemicals are left to work for a period of time before the roof is rinsed with low pressure water. This method requires special training and the use of a professional roof cleaning crew to ensure that the chemicals are applied correctly, are safe for your plants, trees and animals, and are rinsed properly.

If you are selling your home, a professionally cleaned and treated roof can significantly increase its resale value as prospective buyers will be impressed with how fresh and clean the property looks from the ground and through the window. However, it is important to note that a roof that has been chemically treated should never be rinsed with high pressure water as this may result in dislodging the granules of asphalt shingles.

Most roof cleaners use a low dilution of commercially available, household strength sodium hypochlorite (pool chlorine). Some also use other chemicals such as TSP, enhancers and alcohol. While these solutions are effective at killing and removing most organisms, they can be very corrosive to metal roof fasteners, gutters and rubber fittings – especially if the chemicals are not rinsed properly. Additionally, these chemicals can void a roof warranty and may even damage landscaping and other vegetation in the surrounding area due to runoff.

Many roof cleaning companies also offer a soft washing service that utilizes a more gentle and lower concentration of cleaning chemicals. This can be an excellent option for delicate surfaces that are not suitable for high-pressure washing such as wooden panels and screens. These methods can also be used to clean surfaces that require a more immediate results such as those with organic stains, mildew and algae growth.

One such product is Benz Lightning Cleanze which is a non-corrosive, biocidal solution that works well for most types of roofing materials including shingle and tile. It is also ideal for non-porous natural and man-made slate.


Although modern asphalt shingles are designed to be less prone to moss and algae growth as well as those unflattering black streaks, environmental factors and lack of regular cleaning can take their toll. Not only are these stains cosmetically unsightly, but they can also cause roof damage that may result in water leaks and costly home repairs.

One of the most effective methods to keep your roof clean and free from these unwanted organisms is through soft washing. This process involves a low-pressure application of biodegradable chemicals that can be mixed with water to thoroughly remove any spores and dirt that have accumulated on your roof. During a soft wash, the cleaners can penetrate all nooks and crannies of your roof, killing algae, mildew, mold, moss and lichen at the cellular level.

The chemical ratios used for a proper wash will vary depending on the current state of your roof. Since most homeowners will only have access to a much less concentrated bleach solution (typically hardware stores will only sell you solutions at 6.5% compared to the 12.5% Sodium Hypochlorite/Pool Shock that is used by professionals), it is recommended to hire a professional to assess your roof and determine which ratio of bleach to water will be necessary.

When bleach is mixed with water it forms a Hydrogen Chloride ION that battles with the organic matter on your roof (i.e. the spores and algae). After this battle, the Hypochlorite ION will have degraded and all that remains is bleach. It is important to rinse well to remove all the bleach from your roof and prevent a potential reaction with the plants, trees and grass around your house.

During your rinse, it is important to check and make sure that all gutter downspouts are fully open to prevent any rinsing into the landscaping surrounding your home. It is also important to inspect your garden and any other outdoor landscaping for the presence of bleach runoff, which can be deadly to plants. Once the rinsing is complete, your roof will be safe to use and should last 3-5 years, unless the environment surrounding your home requires frequent washing, such as if you are located under a lot of canopy, or has problems with storm residue build up on the roof (valleys etc). If this is the case then the roof will require more frequent cleaning.