Black Roof Stains?
What Homeowners Should Know.

Ugly black or green roof stains can make your home look older and poorly maintained. In many cases, those dark streaks are caused by airborne algae that settle on asphalt shingles. According to the Asphalt Roofing Manufacturers Association (ARMA), Gloeocapsa magma is one of the most common algae associated with brown or black roof discoloration. This is especially true in warm, humid regions and along the Eastern Seaboard. 

That said, not every roof stain means your shingles are being “eaten.” Algae discoloration is often first noticed as a cosmetic problem. Moss and lichen can create different concerns depending on the roof system and manufacturer guidance. ARMA specifically separates algae discoloration from moss and recommends consulting the shingle manufacturer for information about moss growth and removal. A more accurate message for homeowners is this: if you see black streaks, moss, or lichen on your roof, it is smart to address the issue early. Otherwise, buildup becomes harder to remove, and moisture-related problems can get worse.

Roof cleaning is also not a casual DIY project. ARMA warns that roof cleaning can be dangerous and recommends trained professionals for this work. The CDC’s NIOSH ladder safety guidance adds that ladder falls are a persistent hazard both at work and at home. Each year, there are more than 100 deaths and thousands of injuries in the U.S.

When it comes to asphalt shingles, ARMA says algae discoloration may be lightened by applying a solution of liquid household bleach and water. It also says that mixing directions can vary by manufacturer. Furthermore, other cleaning chemicals or methods should not be used without the shingle manufacturer’s approval. In other words, the safest homeowner guidance is not “there is only one method for every roof.” Instead, asphalt shingles should be cleaned using manufacturer-aligned methods, and aggressive alternatives should be avoided.

ARMA’s published process says the solution should be gently applied, left on the roof for about 15 to 20 minutes, and then rinsed off by gently spraying the surface with water. That matters because some online roof-cleaning advice skips the rinse step or treats it as optional. ARMA does not.

Just as important, ARMA clearly says not to use a power washer, brush, or broom on asphalt shingles. High-pressure washing can damage asphalt roofing and loosen protective granules. This is why pressure washing a shingle roof is generally the wrong approach to removing algae. If a contractor proposes cleaning asphalt shingles with high pressure, that should raise a red flag.

Homeowners should also be cautious about one-size-fits-all claims. Roof staining often develops more noticeably on shaded or moisture-prone roof sections. However, treatment decisions should be based on the roof’s actual condition, the manufacturer’s guidance, and the contractor’s process—not on scare tactics or upselling. A reputable contractor should be able to explain exactly what is growing on the roof, how it will be treated, and why that method is appropriate for your shingle type.

If you are thinking long term, roof maintenance is not just about appearance. Cleaning visible staining and organic growth the right way can help preserve curb appeal and support ongoing roof care. In addition, it can make it easier to spot developing roofing issues before they turn into bigger repairs. ARMA also notes that cleaning is only temporarily effective and that discoloration can recur, which is why regular inspection and maintenance matter.

At A+ Power Washing, we have been serving homeowners in Monmouth and Ocean Counties since 1990. The company highlights 36 years in business, more than 110,781 satisfied clients, and over 1,400 five-star Google reviews. If your roof has black streaks, algae staining, moss, or lichen, our team can help you understand your options and recommend the right next step for your home.

If you’d like a free, no-obligation consultation with one of our friendly Customer Care Specialists, please call 732-775-1242. Your home may not be brand new, but we’ll help it look like it is.