As spring arrives in Michigan, many homeowners notice unsightly black streaks appearing on their roofs. While they might seem like mere dirt or shadows, these streaks are often a sign of something more concerning: roof algae.
What Causes Those Black Streaks?
The primary culprit behind these dark stains is a type of cyanobacteria known as Gloeocapsa magma. Despite being commonly referred to as algae, this bacterium thrives in humid environments and feeds on the limestone filler found in many asphalt shingles. Over time, it forms a dark, UV-protective coating, resulting in the streaks you see.
Why Should You Be Concerned?
While roof algae might start as a cosmetic issue, if left untreated, it can lead to:
- Reduced Roof Lifespan: The bacteria retain moisture, which can accelerate the deterioration of roofing materials.
- Decreased Energy Efficiency: Darkened roofs absorb more heat, potentially increasing cooling costs.
- Lowered Property Value: Visible algae can detract from your home’s curb appeal.
ARMA’s Suggested Cleaning
The Asphalt Roofing Manufacturers Association (ARMA) recommends a gentle cleaning solution to remove algae:
- Cleaning Solution: A 50/50 mix of household-strength sodium hypochlorite (bleach) and water.
- Application Method: Apply the solution gently and allow it to sit for 15-20 minutes before rinsing thoroughly with water.
Important: Avoid using high-pressure washing, as it can damage shingles and void warranties.
C A U T I O N:
Although this is the suggestion by ARMA, in our research and experience, we have found conflicting effects about bleach.
Using bleach to clean your roof might seem like a quick fix for algae or moss, but it can actually do harm. As you can see in these pictures, bleach can dry out and damage asphalt shingles, leading to granule loss and a shorter roof lifespan. The picture shows that the homeowner washed the dormer, but not the rest of the roof and there is granule loss, dryness, and discoloration.
It’s also harsh on your landscaping—runoff can burn your grass, flowers, and even trees. On top of that, bleach is corrosive to metal, so it can eat away at your gutters, flashing, and vents over time. The fumes aren’t great for your health either, and if you’ve got pets around, it’s even riskier.
Plus, when bleach washes off your roof, it can end up in storm drains and harm local waterways. If you’re looking to clean your roof, it’s worth considering safer, roof-friendly alternatives like soft washing or using products made specifically for roof cleaning.
Preventing Future Algae Growth
To keep your roof looking its best:
- Zinc or Copper Strips: Installing these near the roof ridge can inhibit algae growth.
- Regular Inspections: Schedule periodic roof check-ups to catch and address issues early.
- Proper Ventilation: Ensure your attic is well-ventilated to reduce moisture buildup.
Trust BC Exteriors for Your Roofing Needs
At BC Exteriors, we understand the challenges Michigan homeowners face. Our experienced team is here to help you maintain a clean, durable, and algae-free roof. When you are ready for a comprehensive roof inspection, we’re just a call away.
Contact us today at 248-688-0211 to schedule your roof assessment and ensure your home remains in top condition this spring.