Roof discoloration happens for various reasons. Some are purely cosmetic, though they can diminish your home’s curb appeal. Others are symptoms of serious damage that can shorten the lifespan of your roofing system. Either way, a quick diagnosis of the problem can be achieved by determining the color and its location on your roof.
In today’s blog, local roofing contractor Roof Recovery provides a quick guide to roof stains. Here, we’ll discuss the different stain colors and what they mean, as well as tips on how to remove and prevent them from appearing in the first place.
A Closer Look at Roof Stains
The following is a list of stain types based on color and appearance, the roofing material involved and its location in your home, and the primary cause:
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Black or Green Stains Caused by Algae
Algae growth is common on surfaces of residential roofing systems, including asphalt shingles, concrete and clay roof tiles and even slate. Closer identification helps reveal the type of organism involved. Green stains usually indicate the presence of green algae, but with dark stains, it could either be actual algae or a type of bacteria called Gloeocapsa magma.
As an airborne bacteria, Gloeocapsa magma or more known as green-algae can easily thrive on rooftops, which have all the essentials necessary for their survival—moisture, sunlight, and a relatively undisturbed surface. The black streaks seen on the roof surface are secretions the bacteria make to protect themselves from the sun’s ultraviolet rays. They also consume tiny amounts of crushed limestone, which is a major component found in the protective granules that coat the surfaces of asphalt shingles. Fortunately, this doesn’t harm the roofing material and is thus deemed a cosmetic or an aesthetic issue.
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Black Stains Due to Extractive Bleeding
Extractive bleeding is a type of product defect occurring in asphalt shingles and other roofing materials. It is caused by the loss of black pigment in the asphalt mix that comprises the shingles’ base mat. Characterized by black stains, it is often confused for green or black algae or even soot. A reliable roofer should be able to make that distinction during a thorough inspection.
Extractive bleeding on roof shingles originates from at least one point on the roof surface. If you see black streaks running down the roof from a single spot, it is probably a so-called “bleed-through,” which is a product defect described by manufacturers as cosmetic.
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Stains from Roof Debris
Organic debris such as dead leaves and twigs can leave black, brown or grey stains on the roof surface. Decaying debris may encourage the growth of fungi, algae, and even thick moss or lichen. Because they hold moisture, any of these can prevent the roof from drying and, in cold climates, hasten the wear and tear of the roof surface by freeze-thaw cycling.
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Roof Stains Around Chimneys
Black stains appearing below and in line with the chimney come from soot from fireplace flues washing down onto the roof. The same pattern may also appear on homes with oil-fired heating flues, which indicates an issue with the heating system. Soot washed down from flues connected to a gas-powered appliance, however, means there is an increased risk of carbon monoxide production inside the home. Immediate action is required in this instance.
Red stains on roofs often come from rusted metal components like flashing, chimneys and chimney rain caps. Chimney exteriors with masonry surfaces are also prone to white or light yellowish-white stains called efflorescence, which is a mineral salt left on the surface as the water evaporates. Like the other stains mentioned above, it is usually an aesthetic issue. Wind-carried rain wets the sides of the masonry, leaching out mineral salts when it dries. Further inspection, however, is needed to check if the water is running inside the chimney flue or structure.
Getting Rid of and Preventing Roof Stains
Cleaning methods vary depending on the type of roof stain involved. Ugly black streaks caused by Gloeocapsa magma can be removed by spraying the roof with a 1:1 ratio of water and chlorine bleach. A garden hose is enough, but if you choose to use a pressure washer, make sure to use a low-to-medium nozzle and spray no closer than 10 inches from the roof’s surface. Leave the solution for up to 20 minutes before rinsing. Alternatively, you can use commercial algae-fighting cleaners that you can purchase off-the-shelf or online. Make sure that you read the instructions on the label before using them.
When cleaning the roof, be sure to observe safety at all times. It is best to do the job on a cloudy day to prevent the cleaner from evaporating too quickly. Since you’ll be using harsh chemicals, see to it that your eyes and skin are well-protected. Cover bushes and other plants with plastic, too—the bleach solution will run down your roof. However, working on a roof can be dangerous, especially if it is wet. Rather than put yourself at risk, consider hiring a professional that offers roof cleaning services.
Investing in asphalt shingles that incorporate algae-resistant granules is one preventative measure to consider. If you are looking to replace your roof, taking advantage of this technology will help keep your roof beautiful and free of stains for years to come.
If you are dealing with debris that has collected on your roof, make sure you clear them regularly with a leaf blower or any similar, non-abrasive method. You can, however, prevent debris staining further by trimming tree branches back. In doing so, you allow more sunlight to reach your roof and prevent the surface from accumulating moisture, which can compromise your roof’s longevity and performance.
Gutter cleaning should be a regular part of your home maintenance routine. By removing dead leaves and other organic matter, you not only promote water drainage but also prevent gutters from an upper roof to overflow and leave stains on the lower parts of the roof system.
For your roof repair and replacement needs, turn to Roof Recovery. We are a family-owned and -operated roofing company dedicated to providing high-quality workmanship and outstanding customer service to local homeowners. Give us a call at (916) 678-9786 or fill out our contact form to request a free, no-obligation estimate.
