Mold and algae look very similar when seen on a roof, yet they have completely different effects. Roof contractor Achten’s Quality Roofing shares an in-depth look at the differences between mold and algae and how you can eliminate them from your roof.
Mold and Algae Look Almost the Same
When seen from the ground, mold and algae both look like black growths that grow on wet spots. They both grow from airborne spores, they spread quickly, and they form dark stains that look obvious especially on light-colored roofs. An untrained eye can easily mistake one for the other, especially when seen from the ground.
The Differences Between Mold and Algae
Knowing the difference between mold and algae is important because what gets rid of one doesn’t necessarily get rid of the other. Algae is a type of bacteria that thrives on moisture and survives even when exposed to sunlight. A certain species of algae, Gloeocapsa magma, also known as “blue-green algae” has a dark “skin” that protects it from direct sunlight. It also forms streaks when rainwater hits the roof. Despite its hardiness, mold doesn’t affect the roof’s performance and it’s unlikely that you will need to have roof replacement done any time soon.
Mold, on the other hand, is a type of fungus that thrives in dark environments, and rarely grows on open surfaces such as the roof. This means if it is present on the roofing surface, there’s more of it elsewhere, likely within the attic.
How to Get Rid of Mold and Algae
The good news is that neither mold nor algae can cause real damage to the roof. Professional roof cleaning services can easily eliminate mold and algae, but make sure the cleaner does not use high-pressure washers. Otherwise, they may leave the roof damaged. Algae can be killed using zinc strips installed at the ridge, dispersed by rainwater. Products like GAF StainGuard Plus™ Shingles feature algae-resistant granules.
Mold is a bit more difficult to get rid of since you will have to inspect areas such as the attic to root out where it is coming from. Make sure you wear a breathing mask before you perform your inspection. Since mold thrives on warm and moist environments, you will need to control sources of moisture, such as roof leaks and increased humidity.