How Mold, Mildew, Moss, Lichens, and Algae Affect Your Roof

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Old Roof — St. Marengo, IL — Jerry Newman Roofing & Remodeling Inc.While mold, mildew, moss, lichens, and algae may seem innocuous or even charming in natural settings, their presence on your roof can have detrimental consequences. These unsightly invaders can wreak havoc on your home and family members. Here is an overview of the hidden dangers of these organisms and how you can safeguard your roof from these unwelcome intruders.

Mold and Mildew

Mold is typically slippery and ranges from black and brown to dark green. It has a strong odor that is impossible to ignore and may quickly break through porous materials like drywall, wood, and plastic. Mold is one of the most dangerous fungi since it may spread through the air and cause major illness.

On the other hand, mildew can be any shade from pale gray to dark pink or even black. It thrives in warm, damp areas with little drainage. It has similar health risks and can spread rapidly.

Mold spores can flourish in an environment where fungi are on your roof. This is due to their ability to soak up excess humidity. Mold spores can float through the air and get inhaled, eventually causing various health issues.

Consequently, you must take precautions to keep mold and mildew off your roof. These precautions can include adequate ventilation, regular roof cleaning, and professional maintenance to remove any accumulated vegetation.


Moss is a genus of non-flowering plants that thrives in damp environments. Because roofs often harbor moisture and debris, moss frequently accumulates on top of homes.

Moss is especially hazardous to roofs since it not only gathers soil, fallen leaves, and debris but also retains water on the shingles, which causes the roof to deteriorate more quickly. This can cause dry rot, which shortens the lifespan of your roof, and early degradation of the roofing materials.

Routine roof maintenance will keep moss from taking root on your roof. Always remove debris such as foliage, dirt, and twigs from asphalt rooftops.

Furthermore, be careful while using a brush or power washer to prevent damage to the roofing material, as you can remove the moss together with the shingles. Finally, position your roof to receive as much sunlight as possible during the day. This will help to reduce the amount of moss on your roof.


Lichens are exceptionally resilient organisms and can thrive in various unfavorable situations. This is why you’ll frequently find them atop buildings. Lichen thrives on roofs because water can easily reach the surface, and the environment is rarely completely sealed.

Lichens can colonize asphalt shingles, wooden shingles, and cement tiles. They are predominantly seen on the tops of ridges and are typically a glaring white or bright yellow.

Roofs with lichen growth often have higher moisture levels, which invites damage, degradation, and mold growth. It can also cause the roof’s insulation to degrade.

You can protect your roof’s integrity with routine inspections for the presence of lichen and promptly remove any discovered lichen growth.


Algae is a form of plant-like organism that is typically blackish-green in color and flourishes in moist environments, which makes roofs a common location for its growth. Because algae thrive and proliferate in damp, warm environments, they are typically more obvious on the roof’s sunny side. Algae can be either discrete black spots or a homogeneous green film over roof shingles.

Algae may not usually cause significant damage to the roofing system, but they are still an eyesore and a nuisance. The summer months’ high temperatures and humidity levels combine to foster rapid algae growth. Thus, you will need a thorough cleaning to discourage algae growth and maintain your roof’s attractive appearance.

Algae are the most common cause of black roof streaks, but tannin staining from branches or trim can also contribute to the problem. Therefore, determine what caused the streaking before you settle on a treatment.

If these organisms significantly affect your roofing system, you might need a roof replacement. Contact us at Jerry Newman Roofing & Remodeling Inc for roofing services in Northern Illinois.

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