5 Dangers of Roof Moss and the Best Removal of Moss on Roof Solutions

1. Roof Moss Holds Moisture That Can Lead to Rot

Roof moss soaks up rainwater and holds on to it, like a sponge. This water that is trapped between the moss and the surface of a commercial roof makes it perfect for rot to start.

Water can slowly seep into the roof layers, like the membranes and decking, when it doesn't have anywhere else to go. This can cause the wood to rot and the insulation to get wet over time, which makes your structure less energy efficient and can make your heating and cooling costs go up.

The National Research Council of Canada (NRC) warns that moisture stuck in building materials can cause mold growth and weaken the structure—something that’s especially common in damp areas like British Columbia.

That’s why moss removal is so important. Taking care of roof moss early and investing in the proper removal of moss on roof surfaces can help protect your property from serious water damage.

2. Moss Can Lift Shingles and Cause Roof Trouble

When moss on roof areas starts to grow, it doesn’t just stay in one spot. It grows out, and its small roots get under roofs or roofing membranes. Over time, this might raise parts of your roof and break the seal that keeps water out.

This is even riskier for flat commercial roofs. A small gap is all it takes for water to get in, which can lead to leaks inside and even mold problems.

Letting roof moss grow without dealing with it early on can wear down your roof faster than normal. If you ignore moss removal, you’ll probably end up with bigger repairs later. That’s why it’s a good idea to take care of the removal of moss on roof spots early—before it turns into a costly problem.

3. Freeze-Thaw Cycles Can Crack Your Roof

If you live somewhere cold, moss on your roof can be more than just a green patch—it can cause real damage. Moss holds onto moisture, and when the temperature drops, that moisture freezes and expands. This can lead to tiny cracks in your shingles or tiles. Then when things warm up, it thaws. But once it gets cold again, it freezes all over—and each time, the cracks get a little worse.

Environment and Climate Change Canada says this freeze-thaw cycle happens most often between November and March, especially in coastal and mountain areas. That’s why moss removal isn’t just for looks—it’s a smart move for roof protection. Making time for the removal of moss on roof surfaces during these months can help you avoid costly repairs later on.

Whether it's killing moss on a roof before winter hits or keeping up with routine cleanups, a little maintenance can go a long way.

4. Blocked Drainage Causes Pooling and Leaks

Most commercial roofs are flat or low-sloped, relying on drains or scuppers to move water efficiently. But when moss clumps form around those drains, water backs up.

This leads to ponding—a condition where water sits on the roof’s surface. Over time, the added weight strains the structure, increases the chance of leaks, and encourages more moss growth.

Routine removal of moss on roof systems ensures that drainage systems stay clear and functional, even during the rainy season.

5. Maintenance Costs Rise Without Early Moss Removal

Delaying the removal of moss on roof only increases long-term costs. A small infestation can be resolved with a basic cleaning. But wait too long, and you may need extensive repairs—or worse, a full roof replacement.

The Canadian Construction Association (CCA) highlights the importance of preventative maintenance as part of effective asset management for commercial buildings—especially when early signs of wear or vegetation appear on the roof.

In short, what seems like a small green patch today could become a six-figure repair job tomorrow.

Best Practices for the Removal of Moss on Roof Systems

If you’ve noticed moss on your roof, don’t ignore it. It might seem harmless at first, but over time, moss traps moisture and can slowly damage your roofing materials—especially on commercial roofs with flat or low-slope designs.

To keep your roof in good shape, here are a few things to keep in mind:

• Avoid pressure washing. It might sound like an easy fix, but blasting water at your roof can do more harm than good. It can strip away protective coatings and cause wear and tear way too early.
• Use gentle tools and roof-safe treatments. A soft brush and a proper moss removal solution made for roofs will get the job done without causing damage.
• Watch shady, damp spots. That’s where roof moss loves to grow. Regular inspections—especially after a rainy season—can catch it before it spreads.
• Call in the pros. For commercial buildings, it’s best to hire experienced roofers. They know how to handle the removal of moss on roof systems without risking damage to your materials.
• Extra care for TPO roofs. If your roof is made of TPO, it’ll need the right follow-up after killing moss on a roof. Without it, the moss can come back—and so can the headaches.

Want more practical tips? Check out this guide: 7 Best Practices for Maintaining TPO Roofing: A Guide for Commercial Roofing in Vancouver. It breaks down what to do step-by-step to keep your roof strong and moss-free.

Killing Moss on a Roof Without Damaging It

If you’re dealing with moss on your roof, it's important to get rid of it without causing harm to the roofing itself. Skip the bleach and strong chemicals—they might work fast, but they can damage materials, especially if you have metal or reflective roofing.

Instead, go for safer options like moss control products made with potassium salts or zinc sulfate. They’re tough on moss but much gentler on your roof. You can also add zinc or copper strips along the roof ridge. These help keep moss from growing back by releasing natural minerals every time it rains.

Final Thoughts: Don’t Wait on the Removal of Moss on Roofs

Roof moss might look harmless at first, but it can cause some serious damage. It holds onto moisture, loosens roofing materials, leads to cracks, clogs your drainage system, and drives up your repair bills.

The best move? Don’t put off the removal of moss on your roof. Taking care of it early helps you avoid leaks and expensive fixes later on. If you haven’t already, schedule a roof check—and keep your building in good shape for the long run.