Why Are My Roof Shingles Turning Black? (What to Do Next)

If you’ve noticed black streaks or spots on your roof, you’re not alone. This common issue can cause alarm and often prompts homeowners to wonder about the underlying reasons and potential solutions.

Today, we’ll explore:

• The various factors contributing to black discoloration on roof shingles
• The causes
• Practical advice on how to address the problem

By the time we’re done, you won’t ever have to ask yourself “Why are my roof shingles turning black?” ever again!

Understanding the Basics of Roof Shingles

Before delving into why your roof shingles may be turning black, it’s essential to understand what roof shingles are and the materials they are made from.

Types of Roof Shingles

• Asphalt Shingles: The most common type of roofing material in the United States, comprised of a base mat, asphalt coating, and granule surface.
• Wood Shingles and Shakes: Made from cedar, redwood, or other types of wood, they provide a natural appearance.
• Metal Shingles: Made from materials like aluminum, copper, or steel, they are known for their durability.
• Slate Shingles: Made from natural stone, they offer a distinctive and long-lasting roof.
• Tile Shingles: Are made from clay or concrete, and are known for their aesthetic appeal and durability.

4 Common Causes of Black Streaks on Roof Shingles

Black streaks on your asphalt roof shingles can be caused by a variety of factors, including:

1) Algae Growth

One of the most prevalent causes of black streaks on roof shingles is algae growth. More specifically, the blue-green algae known as Gloeocapsa magma.

How Algae Grows on Roofs

• Spores Travel by Air: Algae spores can be carried by wind, landing on roofs and beginning to grow.
• Moisture Attracts Algae: In regions with high humidity or frequent rainfall, moisture can accumulate on the roof, providing an ideal environment for algae.
• Shaded Areas: Roofs shaded by trees or other structures are more susceptible to algae growth due to the reduced sunlight and increased moisture retention.

The Impact of Algae on Roof Shingles

• Aesthetic Issues: While algae itself does not necessarily harm the roof, it creates unsightly black streaks that can affect the home’s curb appeal.
• Heat Absorption: Algae-covered shingles may absorb more heat, leading to increased cooling costs.

2) Mold and Mildew

Mold and mildew can also cause black discoloration on roof shingles, particularly in areas with high moisture levels.

Conditions Favoring Mold Growth

• Poor Ventilation: Inadequate roof ventilation can trap moisture, fostering mold growth.
• Organic Debris: Leaves, branches, and other organic matter can retain moisture on the roof, promoting mold and mildew growth.

Risks Associated with Mold and Mildew

• Structural Damage: Over time, mold and mildew can degrade the roofing materials, potentially leading to leaks.
• Health Concerns: Mold spores can be harmful to individuals with respiratory conditions or weakened immune systems.

3) Asphalt Bleeding

Another potential cause of black streaks is asphalt bleeding, where the oils and compounds within asphalt shingles migrate to the surface.

Causes of Asphalt Bleeding

• High Temperatures: Extreme heat can cause the asphalt to soften and bleed.
• Age and Wear: Older shingles may be more prone to bleeding as the materials break down.

Consequences of Asphalt Bleeding

• Aesthetic Impact: Similar to algae, asphalt bleeding can create unsightly black streaks.
• Potential for Damage: While generally less damaging than mold or algae, bleeding shingles may indicate underlying wear and tear.

4) Airborne Contaminants

Airborne contaminants, including dirt, dust, and industrial pollutants, can settle on roof shingles, leading to discoloration.

Sources of Contaminants

• Proximity to Urban Areas: Homes near industrial zones or busy roads may experience more significant contamination.
• Environmental Factors: Dust storms, wildfires, and other environmental events can deposit particles on roofs.

Effects on Roof Shingles

• Visual Impact: Over time, these contaminants can contribute to a darkening of the roof’s surface.
• Potential for Chemical Reactions: Certain pollutants may react with the roofing materials, accelerating wear.

How to Address and Prevent Black Streaks on Roof Shingles

Luckily, there are lots of ways to take care of your asphalt shingle roofing, even if black streaks make and apperance.

Regular Cleaning and Maintenance

Consistent cleaning and maintenance can prevent the buildup of algae, mold, and other contaminants.

Cleaning Methods

• Soft Washing: Employ a low-pressure sprayer with a mixture of water, bleach, and detergent. This effectively removes algae, mold, and mildew without damaging the shingles.
• Power Washing: Use a high-pressure washer to blast away contaminants. This must be done carefully to avoid damaging the shingles.
• Professional Roof Cleaning Services: Hiring professionals ensures proper techniques and safe handling of cleaning agents.

Installing Algae-Resistant Shingles

Many manufacturers now offer algae-resistant shingles, treated with copper or zinc granules that inhibit algae growth.

Benefits of Algae-Resistant Shingles

• Long-Term Solution: Provides a lasting defense against algae.
• Enhanced Aesthetics: Maintains the roof’s appearance over time.

Improving Roof Ventilation

Proper ventilation reduces moisture buildup, preventing mold and mildew growth.

Ventilation Solutions

• Ridge Vents and Soffit Vents: Allow air to flow through the attic, reducing moisture.
• Attic Fans: Enhance ventilation in areas with limited natural airflow.

Trimming Overhanging Branches

Reducing shade on the roof by trimming overhanging branches can minimize moisture retention and inhibit algae growth.

Applying Roof Coatings

Roof coatings can protect shingles from contaminants and reduce the risk of discoloration.

Types of Roof Coatings

• Reflective Coatings: Reflect sunlight, reducing heat absorption and protecting against UV damage.
• Algae-Resistant Coatings: Contain biocides that prevent algae growth.

Routine Inspections

Regular roof inspections can identify potential issues early, allowing for timely intervention.

Inspection Checklist

• Check for Algae and Mold: Look for signs of black streaks or spots.
• Examine Shingle Condition: Assess for signs of wear, bleeding, or damage.
• Inspect Gutters and Downspouts: Ensure proper water drainage to prevent moisture buildup.

Prevent Algae Growth With Whitt’s

Black streaks on roof shingles are a common issue caused by various factors, including algae growth, mold, asphalt bleeding, and airborne contaminants. Understanding the underlying causes and taking proactive measures can help maintain your roof’s appearance and integrity.

If you’re experiencing persistent issues with black streaks on your roof, consider consulting a professional roofer to assess the situation and recommend appropriate solutions. Taking action now can save you from more significant problems down the line and ensure that your home remains protected and visually appealing.

Contact Whitt’s Quality Roofing today to remove black stains and get your roof looking its best again.