Algae Removal

Algae & Moss Prevention and Cleaning

To understand the best ways to handle the recurring issue of algae and moss growth on rooftops, it is essential to learn what they are and how they grow and spread. There are some similarities between both moss and algae, they are quite different and therefore, require different procedures to eliminate and avoid future buildup.

Frequently mistaken as mold or mildew, the black discoloration and streaks noticeable on most roofs in North Carolina are actually algae. The algae can form where moisture has the tendency to cumulate on roofing surfaces. Coastal or humid environments, similar to this area, produce the most favorable conditions for algae development. The most typical type is a blue green algae referred to as gloeocapsa magma and will safeguard itself from harmful ultraviolet rays by producing a dark pigmented sheath. The discoloration caused by this algae starts as little areas then quickly changes into streaks on the roofing system surface. By the time the algae is visible, it likely has existed for several months or longer.

Algae spores are carried by the wind or by animals and can rapidly spread from one roof to another. That is why it is common to see algae development on rooftops throughout an afflicted community. The very same holds true for condo or apartment or within HOA areas, townhouses or row houses. There is no clinical proof that algae are harmful to asphalt shingles, although it definitely affects the aesthetic appeals of a roof. On highly reflective or what is referred to as a “cool” roof system, algae will have an unfavorable effect on the long-lasting effectiveness of these roof systems. This makes it very important to deal with an algae problem as quickly as possible.

Unlike most plants that gather water through its root system, moss is a non-vascular plant which acquires water through its leaves. For this reason, moss needs a moist environment to survive and grow. In North America, moss has the tendency to grow on north facing roofing surfaces that have less direct sunshine and usually stay wet longer than south facing areas. Trees that overhang your roof area offer additional shade and drop particles on the roofing that further holds in wetness and serves as a food source for moss.

Wind and animals also carry moss spores and can quickly spread through a neighborhood. Moss can be destructive to asphalt shingles, unlike algae. Left unattended, moss can cause the edges of asphalt shingles to curl or lift up from the tarp underneath. This increases the risk of shingle blow-off during strong winds such as storms or hurricane weather conditions. In extreme cases, moss build-up can trigger lateral water motion resulting in wetness damage to the roof deck or may even trigger leakages.

The most reliable method of cleaning algae and moss from a roofing system is with an equal mix of water and household laundry liquid chlorine bleach. Apply with a sprayer and enable the solution to sit on the roofs surface for approximately 20 minutes, and then wash thoroughly with low pressure water. Longer wait times may be needed, nevertheless, avoid letting the solution dry entirely as this might avoid total rinsing. Take proper safety measures to protect landscaping and surrounding shrubs and plants from the chlorine bleach option. Use suitable individual protective equipment when working with chlorine bleach. Any leftover algae will be washed away with rain. Over time, moss will loosen and can be eliminated with a leaf blower. In serious cases, it might take more than one bleach treatment to kill all of the moss. Never use a pressure washer to clean up an asphalt shingle roof as this will cause granule loss and most likely premature failure of the roof system.

A+ Pro Services has a few tips to add to your home maintenance which will help to eliminate moss and algae growth:

Keep rain gutters clean to promote correct water drain. Do not allow gutters from an upper roof area to drain through pipes to a lower roofing system; extend the downspout from the upper roofing system into the lower rain gutter.
Trim tree branches to allow more sunshine to reach the roof and lessen debris build-up will provide an environment less inviting for such development
To avoid driving debris under the edges of the shingles air flow should be directed down the slope.

Debris that does begin to accumulate on the roofing should be cleared frequently with a leaf blower or similar device as a non-abrasive approach as part of a routine upkeep program.

Other preventative measures– such as including cooper or zinc strips to avoid both algae and moss, or using asphalt shingles that include algae resistant copper granules– may be employed when it is time to replace a roof. Presently, there are asphalt shingles available that use algae resistance innovation.

It is not a good idea to copper or zinc strips to an existing roof as this will probably require applying the strips with exposed nails (which over time may cause a leak) or breaking the sealant bond (which might eventually result in wind damage) to slide the strips under the shingles.

Algae and moss development on roofing systems, at a minimum, is an unattractive problem. If left unattended, moss buildup can cause damage to your roof or shingle blow-off if left unattended. Part of a regular roof maintenance program should include keeping branches trimmed from the roofing and eliminating any particles that begins to build up. If moss or algae ends up being visible, clean the roof with water and bleach mix as explained above to avoid the infect close-by roofs.

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