Protect your roof from moss, algae, and mold damage
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.
1. Trim Overhanging Trees
Sunlight and circulation are your roof’s best weapons against any organic growth. Trim back tree branches to allow Mother Nature’s sunlight and air to reach your roof. Avoid letting anything sit on your roof — like tarps or branches — for long periods of time. If your roof stays damp and shaded, that's a prime breeding ground for mold and algae.
2. Clean Your Gutters
Proper water drainage from your roof will not only help keep it free from algae growth, but (bonus benefit!) it will also help keep your foundation at the foot of your home solid. Clogged gutters can cause water to back up onto the roof. When that water pours down around your foundation, basement leaks now become a concern. Make sure the gutters are clean and downspouts clear so water drains away properly.
3. Keep Roof Clear of Debris
This may sound like a simple one, but it’s probably the most effective. As leaves and debris commonly accumulate on your roof, they hold moisture and create a breeding ground for mold and algae. Use a leaf blower to simply remove any of these uninvited guests. We’d recommend avoiding the use of a pressure washer – it’s dangerous and may actually void your roof’s warranty protection.
4. Improve Attic Ventilation
Your attic can rise to pretty oppressive temperatures if not ventilated correctly. That hot, stale air sitting in your attic provides an unfortunate foundation right under your roof to encourage mold and algae growth. Ensuring your attic is well ventilated will help keep your roof consistently dry.
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.