Introduction
Organic growth on roofs—like moss, algae, mold, and lichen—is a common issue, especially in damp or shaded areas. While it might look harmless at first, this growth can damage roofing materials, leading to costly repairs or even premature replacement. In this blog, we’ll cover what causes organic growth, why it’s a problem, and most importantly—how to handle it.
Why Organic Matter Grows on Roofs
Several conditions encourage the growth of moss, algae, and mold:
- Shade: Overhanging trees or tall buildings block sunlight, keeping the roof moist longer.
- Moisture: Rain, humidity, and poor drainage create a damp environment perfect for growth.
- Debris: Leaves and twigs trap moisture and organic particles that feed algae and moss.
Prevention Tips
Trim Overhanging Trees
- Keep trees trimmed to let more sunlight reach your roof.
- This helps the roof dry faster after rain and reduces leaf litter.
Clean Your Gutters
- Clogged gutters can cause water to back up onto the roof.
- Clean them at least twice a year (or more if you live near trees).
Keep Roof Clear of Debris
- Use a roof rake or leaf blower to remove leaves, branches, and pine needles.
- Debris holds moisture and can act as a seedbed for moss and algae.
Improve Attic Ventilation
- A well-ventilated attic helps regulate temperature and moisture.
- Less trapped heat and humidity = a drier roof.
Cleaning Methods (Safely Removing Existing Growth)
If you already have moss or algae:
- Low-Pressure Washing: Avoid high pressure that damages shingles.
- Mild Cleaning Solution: A mix of water and bleach (or hiring a professional roof cleaner) can kill growth. Rinse thoroughly.
- Copper or Zinc Strips: Install these at the roof ridge. Rainwater running over them creates a surface that resists organic growth.
Note: Always prioritize safety or hire professionals if your roof is steep or hard to access.
What Not to Do
- Don’t use a pressure washer on asphalt shingles—it can strip granules and reduce lifespan.
- Avoid walking on your roof unnecessarily. It's dangerous and can damage roofing materials.
- Don’t let moss "just be." It holds moisture and spreads quickly.
Keeping organic matter off your roof is all about reducing moisture, increasing sunlight, and keeping surfaces clean. A little preventive maintenance can go a long way in protecting your roof, improving your home’s appearance, and saving money in the long run. As with any project, your safety is of utmost importance. Always hire a professional should you have any concerns for your safety. It’s best to always err on the side of caution to keep your house looking its best.