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Why it’s important to keep your roof clean

Posted on by Platinum Roofing

When the siding on the exterior of your home is dirty, or the paint is peeling, it makes your entire house look dingy.  As homeowners, we know we’re expected to keep our homes looking nice — no one wants to come home to a mess, and no one wants to own the house that the neighbors grumble about whenever they drive past. That includes roof cleaning. Not only can a dirty roof ruin your home’s curb appeal, but it can damage your roof.

More than Dirt

Your roof is exposed to the elements all day, every day. Dirt and debris will collect on it. Natural rainfall is typically enough to wash off the appearance of most dirt. However, the dark stains and green areas that appear on your roof are caused by other natural elements:
  • Algae
  • Fungus/Lichen
  • Moss
These substances are much trickier than simple dirt and require some explanation.


Angie’s List explains that the black stains are called gloeocapsa magma or GM. GM algae is a bacterium that feeds off of both asphalt and limestone roofing in moist, cool and shaded areas of the roof. When there is minimal light, GM forms a blue-green color. The more shaded areas of the roof are more likely to have these algae, which can harbor various types of molds. This explains why some roofs are stained only on one side. These algae spores are transported by wind or animals. They can quickly spread from rooftop to rooftop in neighborhoods of single-family homes, townhomes and apartment complexes.


Lichens are basically the combination of algae and fungus. Lichens are a fungus that grows symbiotically with algae. These plant-like organisms form a branching growth of “root-like tentacles that penetrate deep into the shingle’s organic, oil base for nourishment.” Lichens are tough to remove from the roof and can reappear from humidity and rain.


Roof CleaningUnlike the algae and lichens, moss is an actual plant. Moss has a shallow root system and requires a lot of moisture to survive. Areas with less sunlight remain damp longer. Overhanging tree branches not only provide more shade, but they also drop debris that serves as a food source for moss. Like algae, moss spores are often transferred by wind or animals and can easily spread throughout neighborhoods.

How Can Stains Damage a Roof?

The stains and growth patches caused by algae, fungus and moss can damage your roof through shingle deterioration and wood rot. Both lead to expensive repairs and can shorten the life of your roof. A roof cleaning can help minimize or eliminate this damage.

Shingle Damage

As mentioned above, GM algae is a bacterium that feeds off both asphalt and limestone. That means that these organisms are literally eating away at your shingles. Furthermore, roofs with algae stains absorb heat. This results in extremely high heat in the attic, which can reduce the lifespan of the shingles by essentially baking them from the inside out. Lichen colonies can be quite damaging to shingles. The penetrating tentacles create pock marks where they grow and eventually ruin the shingles.  Moss is even more detrimental to roof shingles. Moss can cause the edges of the shingles to lift or curl—often the first sign that a roof replacement is needed. And because moss holds in moisture, it can freeze in the winter, causing even more shingle damage.

Wood Rot

Moss can hold in moisture and divert water, which makes your roof deck susceptible to wood rot and leaks. It tends to grow in the slots between shingles, which is the last place water evaporates from a roof. Moss growth on your roof is easy to spot. But the signs of wood rot are not always obvious to the average homeowner. Wood rot not only shortens the life of your roof, but it can also cause mold growth, which can be hazardous to homeowners and their pets.Do you have guests in your attic or on your roof? Unwanted critters can cause more damage when the wood begins to rot. Animals, such as squirrels, have been known to cause roof and attic damage by chewing through areas of the roof and supporting wood systems. Rotted wood makes it easier for these creatures to bore through.

Professional Cleaning

Roof cleaning not only maintains a beautiful appearance, but it also protects your investment by extending the life of the roof. While it is tempting to make roof cleaning a DIY project, it is recommended to hire a professional roof cleaning company. These professionals use special equipment that does not harm the shingles, unlike standard high-pressure washers. Reputable roof cleaning companies will also use a biodegradable cleaning solution. A DIY roof cleaning project typically uses a solution of water and bleach. While that can help rid the roof of algae, it is harmful to plants and the environment.When looking for a reputable roof cleaning professional, call Platinum Roofing.


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