Moss, Algae, and Lichen: What’s Growing on Your Roof and How to Handle It

Have you noticed green clumps, black streaks, or rough patches forming on your roof? If so, you’re not the only one. Homeowners throughout Rochester—including Henrietta, Greece, and Irondequoit—often deal with moss, algae, or lichen growing on their roofs. While this growth might look harmless at first, it can lead to real problems over time.

At Robertson Roofing, we’ve seen how these organisms can quietly wear down shingles and reduce the lifespan of a roof. This guide will help you understand what’s growing on your roof, why it’s happening, and how to take care of it before it causes damage.

What Are Moss, Algae, and Lichen?

These three types of roof growth may look similar, but each has its own habits and risks.

Moss

Moss grows in thick, green clumps and thrives in cool, shaded areas. It commonly appears on the north-facing side of a roof or beneath tree cover. In areas like Irondequoit or tree-lined streets in Henrietta, moss is a frequent concern.

This type of growth holds moisture against the shingles, which can cause them to lift, curl, or break down over time. If left alone, moss can create the perfect conditions for leaks and rot.

Algae

Algae shows up as dark streaks or stains, especially on asphalt shingles. These streaks are often caused by a type of algae called Gloeocapsa magma, which feeds on the limestone in shingles. It’s commonly spread by wind or rain and tends to show up in humid areas, particularly in neighborhoods with lots of tree coverage, like Greece.

Algae won’t immediately harm your roof, but it can make it look older and worn. It also holds moisture and may help moss or lichen take hold more easily.

Lichen

Lichen is a mix of algae and fungus. It forms crusty, flat patches that can be green, gray, or bluish. Lichen bonds tightly to your shingles, making it difficult to remove. Over time, it can eat into the surface of the roofing material and cause pitting.

Lichen is often found in spots where algae has been present for a while, especially on roofs that stay damp or shaded for long periods.

Why It’s a Problem in the Rochester Area

Our local climate creates the perfect environment for moss, algae, and lichen. We deal with long winters, humid summers, and plenty of rain. When that moisture combines with shade from trees or poor drainage, roof growth becomes a common issue.

Unchecked growth can lead to:

• Shingle deterioration

• Leaks from lifted or cracked shingles

• Mold or mildew in the attic

• Reduced energy efficiency

• A drop in home value and curb appeal

Even if your roof isn’t leaking now, signs of moss or algae could mean future trouble.

How to Handle It

There’s a right way and a wrong way to remove biological growth from a roof. Here’s how Robertson Roofing recommends taking care of the problem safely and effectively.

Keep Your Roof Clear and Dry

Shaded roofs are more likely to grow moss and algae, especially when tree branches hang directly over them. Trimming back overhanging limbs and clearing debris from your gutters helps reduce the moisture these organisms need to survive.

If you live in heavily wooded areas of Irondequoit or Henrietta, regular roof maintenance can make a big difference.

Improve Attic Ventilation

Moisture problems don’t just come from the outside. If your attic isn’t ventilated properly, warm air from inside your home can rise and collect under the roof deck. That trapped humidity can seep into your shingles and support the growth of moss or algae. We’ll check your attic ventilation and recommend improvements if needed.

Prevent Future Growth

Zinc or copper strips installed near the roof ridge can help prevent moss and algae from coming back. When it rains, small amounts of metal wash down the roof surface and create conditions that stop new growth from forming. This small upgrade can keep your roof cleaner for years.

When to Call Robertson Roofing

If you’ve seen signs of growth on your roof—or you’re not sure what you’re looking at—it’s a good time to bring in a professional. Trying to clean it yourself could cause more harm than good, especially if you’re dealing with lichen or heavy moss buildup.

Robertson Roofing provides expert inspections and cleaning services for homeowners across Rochester, including Henrietta, Greece, Irondequoit, and surrounding neighborhoods. We’ll assess the issue and offer clear guidance on what needs to be done.

Take Care of Roof Growth Before It Causes Damage

Moss, algae, and lichen are more than just cosmetic problems. They hold moisture, attract debris, and weaken your roof over time. If ignored, that growth can shorten the life of your shingles and lead to expensive repairs.

Don’t wait until you have a leak. Reach out to Robertson Roofing today to schedule a roof inspection or cleaning service. We’re here to help you keep your roof clean, strong, and ready for the seasons ahead.