Three Reasons Your Roof May Have Discolorations

A discolored roof is an eyesore. This is especially true if the coloration is widespread and visible from the ground. In many cases, the coloration doesn't originate from the roof structures. Here are three examples of things that may color your roof and what to do in each case:

Asphalt Shingle Pigment

The black pigment in shingles can stain your roof in a process known as extractive bleeding. Extractive bleeding occurs when asphalt shingles lose their black pigments, which then streaks down the roof. The pigment is part of the asphalt mix, which means extractive bleeding is an asphalt shingle defect. You should suspect that this is the case if the black streaks originate from single points on the shingles. They also appear on any side of the roof, regardless of orientation and sun exposure. There isn't much you can do about these stains, except to go for high-quality shingles when the time for reroofing comes.


Apart from soot, algae can also stain your roof. You should suspect this kind of staining if the offensive black color only appears on shaded or moist parts of the roof. This is because algae thrive on moisture, and the shade (for example, from tree branches) prevents the roof from drying too fast. Coloration due to algae also tends to be more uniform, as opposed to extractive bleeding that seems to originate from singular points.

Contact a roofing company to clear the algae from your roof. The most common method for this is chemical cleaning (using a cleaner that kills the algae). It's best done by a professional to avoid further damage to the roof. After that, have a roofer install copper or zinc strips below the roof's ridge, on each side of the roof. The metal, which is toxic to algae, will wash down the roof and prevent further algae growth.


Rust may be red or brown. Since rust is oxidized metal, it will only appear on metallic roofs or originate from metallic parts (such as chimneys and antenna mounts) of the roof. However, rust colorations may wash down the roof and color its nonmetallic parts, but the stains will still be confined to areas below and around the metal projections.

Rust can point to a more serious roof problem than the cosmetic defects. Rusted metal tends to be weak and may even have holes. This means rusted parts of the roof are common points of water leaks. It's also not a good idea to walk on or hold onto rusted parts of the roof. It's best to leave it in the hands of a professional roof technician. The usual treatment involves cleaning the roof, repairing any defects (such as leaks), and then painting the roof. Your roof contractor will tell you which treatment suits your roof. For more information, contact a company like Affordable Roof Care.