BRISTLEWOOD Roofing & Remodeling Blog


Growth On Roofs: Mold, Moss, Lichen and What To Do About It

A layer of green moss atop your house might look like something out of a fairy tale, but left unchecked it can be much closer to a nightmare for homeowners. There is no question that with enough time growing organisms on your roof will destroy your shingles, as well as collectively reduce the expected life of your most expensive single component of your home: your roof. Here’s a little information about what’s growing on your roof and what you can do about it:

What’s Growing On My Roof?

The most common natural threats to your roof are: moss, moss, and lichen.

Moss, mold, and lichens are all different types of growth that can be found on your roof. Each of them can damage your roof in various ways.

  • Moss is a bryophyte that develops from water-based plants. A carpet of moss is generally springy to the touch, with short tendrils shooting upwards. While moss requires water to grow, it cannot grow immersed in water.
  • Mold is a fungus that grows in the form of multicellular filaments called hyphae. Molds causes biodegradation of natural materials which can spell disaster for your property.
  • Lichen is a combination of algae and fungi. Lichen is not technically a plant at all, but rather a type of fungus that exists in a symbiotic relationship with algae. There are four types of lichen with varying appearances, and it is easy to mistake lichen for moss.


Mold growth on your roof can be alarming as it is often due to the presence of leaks. Mold tends to thrive in shady, moist conditions. Therefore In rainy, humid weather, algae can take hold causing mold to grow quickly on your roof. This causes the roof materials to remain damp, which can create rot.

Lichen, moss, and/or mold on the roof can shorten the lifespan of your shingles

When rot sets in, so can mold! Even without rain, warm or humid weather can create the ideal condition for quick mold growth.

So what do you do if you find mold on your roof?

There are several ways to clean your roof from mold and algae. Pressure washers can be effective, however they can severely damage the shingles if not done correctly. There are other commercially available cleaning solutions on the market; be sure to check the labels and ensure you’re using the right product for your roof.

Cleaning your roof can be risky. Once on top, make sure to secure yourself in a harness. Most people will get help from a roof repair company for better results. While it’s good to initiate for your roof’s maintenance, getting help from an exceptional roofing company is still your best option.


Moss starts as a thin green layer on and between shingles, but then proceeds to lift those shingles up as it grows, allowing water to seep underneath. Just brushing off moss won’t prevent future growth!

Lichen, moss, and/or mold on the roof can shorten the lifespan of your shingles

If the roof is not properly cleaned you risk damaging the shingles and reducing the life of the roof.

Moss damages your shingles in three significant ways:

  1. Moss can strip away the protective oils on your shingles, making them susceptible to erosion and sun damage. Without proper protection, your shingles will likely warp and crack in the sun, significantly shortening their lifespan.
  2. Moss absorbs water, so every time it rains the moss sucks up more moisture and spreads farther across your shingles, eating away at this outer protective layer. If not properly treated, this moisture buildup will ruin your shingles, and you will eventually need to replace your entire roof.
  3. Moss spreads beneath your shingles and absorbs water, allowing moisture to invade into the interior of your home. When moisture builds up on the inside of your home, it leads to wood rot. This is the worst case scenario as it means far more extensive and expensive repairs to your home.

So what do you do about the moss growing on your roof?

First you must hose off and brush all moss loose from your roof shingles, then apply a DIY cleaning solution to remove the moss.

Much like removing mold, cleaning your roof can be very risky if you don’t know what you are doing. It is extremely important to secure yourself in a harness prior to cleaning. Most people will get help from a roof repair company for better results. While it’s good to initiate for your roof’s maintenance, getting help from an exceptional roofing company is still your best option.


Lichen is an invasive combination of algae and fungus. Unlike moss or mold however, there is no fairy tale upside to lichen. This ugly growth spreads across roofs, walls, and sidewalks; and may grow in a wide range of temperatures and conditions. Just like Moss and Mold, lichen may appear to be harmless but can cause significant damage to outdoor surfaces over time.

Lichen, moss, and/or mold on the roof can shorten the lifespan of your shingles

Lichen on the roof holds moisture against the surface, speeding up the wear and tear and significantly shortening the lifespan of your shingles.

The lichen may also make its way into your roof’s exterior, causing the shingles to separate. Removing lichen from your roof is an investment every homeowner should make, not just for the lifespan of your roof, but removing lichen may reduce homeowner’s insurance rates.

If an insurance inspector sees a dirty, lichen-covered roof, this may give them a reason to raise your rates or even cancel your policy due to the severe damage lichen can cause over time.

Why Is It Growing On My Roof?

Mold, lichen, and moss love to breed in warm moist environments, and that means your roof makes the ideal breeding ground. Left untreated, heavy buildup of plant life and fungi can drastically shorten the lifespan of virtually any roof, regardless of the material.

Roof moss, mold, and lichens are often caused by overhanging trees, clogged gutters, flat roofs with poor drainage, and/or ample shade. Typically these kind of roof problems show up in spring and summer when there’s a lot of rain and humidity.

What Should I Do About It?

If you notice that your roof is growing moss or other fungi, there are several things you can do:

  • Trim overhanging tree branches
  • Wash your roof carefully with a chemical cleaner
  • Install algae-resistant roof shingles which include copper granules to help limit growth
  • Schedule bi-annual roof inspections

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Bristlewood Roofing &

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