Roof leak? Call us.(503) 925-0125

How Moss Damages Your Roof: 4 Things You Should Know

Posted May 12, 2010 by Patrick Morin
Let Us Help

Key Takeaways

  • Moss is a small, nonvascular flowerless plant that typically forms in dense, mat-like green clumps with a spongy feel.
  • The presence of moisture, shade, and organic debris can cause moss and algae to grow on roofs.
  • Moss traps soil and debris that hold water, keeping roofs wet for extended periods. This encourages fungi growth and quicker decomposition of wood.
  • Moss can also cling to roofs’ asphalt and metal materials, compounding until it lifts the shingles and allows water to penetrate and damage the underlying construction.
  • Portland experiences lots of moss growth due to its cool, rainy winters, making the region’s roofs especially susceptible to damage.

Understanding The Effect of Moss on Your Roof

Moss is a type of nonvascular plant with approximately 12,000 species, each with varying forms and geographical prevalence. Due to their cool and wet climates, specific locations, like Portland, Oregon, are extra susceptible to moss growth. Moss can grow on virtually any hard surface, including trees, sidewalks, and roofs. 

Each roof is unique, featuring slightly different materials, designs, and surroundings. Therefore, some roofs are more likely to experience moss growth than others. Although moss can affect wood, metal, and asphalt, it usually impacts each material differently.

Understanding what causes moss growth can help you keep your roof protected. Plus, knowing how moss can hinder the appearance and function of your roof can help you ensure the longevity of your home.

How Moss Grows On Roofs

Moss is a nonvascular flowerless plant that reproduces using spores and grows on almost any hard surface, including trees, rocks, sidewalks, and buildings. Although there are roughly 12,000 different species, moss usually manifests as dense, green-colored mats or clumps that exhibit a fragile, spongy texture.

Moss thrives in cool, wet, and shaded environments. Certain climates, like the brisk, rainy climate in the Pacific Northwest, can cause moss to grow out of control, infiltrating roofs and inviting water damage into homes. Considering areas like Portland, Oregon, are especially conducive to moss growth, local homeowners must educate themselves on the potential impacts of roof moss to prolong the life of their homes.

The three most common forms of roof moss are:

  • Roly-poly moss – This moss has a bright green appearance that makes it look like it’s glowing. It grows on shingles, germinates with high moisture levels, and gets fertilized by organic debris on the roof, encouraging it to grow faster. It can lift shingles and cause water damage throughout your roof.
  • Spindly roof moss – This moss usually comes from laceleaf Japanese maple or birch tree branches that dangle over roofs. It can attach to certain shingles and disintegrate them, damaging your roof.
  • Furry roof moss – This moss can only grow on rotted wood roofs and occasionally tiles. Its presence indicates pre-existing wet rot and decay on your roof, potentially from sitting water.

Considering moisture and organic debris spur most moss growth, performing routine roof maintenance is best. A team of qualified professionals should regularly inspect your roof for moss and other potential dangers to handle problems as they come up, saving you from expensive home repairs.

How Can Moss Damage a Roof?

Since there are different types of moss, there are also several ways that moss can negatively affect your roof, such as raising shingles and making water damage more likely. Noticing initial signs of moss damage is an excellent way to curb the problem before it requires costly, widespread repairs. The following questions are commonly asked by homeowners with roof moss.

How Does Moss Cause Water Damage?

Moss can hold substantial amounts of water, usually achieving maximum water storage capacities of 108% to 2070% of their dry weight. If water-logged moss sits on your roof for extended periods, it can lead to rot, bacteria, and mold growth, which can cause your roof’s construction to decay over time.

How Does Moss Damage Roof Shingles?

Due to the small size of its spores, moss can grow in the cracks between shingles. As the moss expands, it can loosen and lift your shingles, allowing water to enter the vulnerable portions of your roof and damage your home.

Sometimes, shingles may not correctly fit together after removing moss, leaving troublesome gaps. In this scenario, you may have to execute a more extensive roof repair to avoid further damage.

How Does Moss Hinder Energy Efficiency?

If moss growth is unchecked, it can lift or deteriorate shingles, creating holes and leaks in your roof. If your roof isn’t properly sealed and insulated, you may spend more money on utilities to keep your home at an ideal temperature.

<iframe width=”560″ height=”315″ src=”” title=”YouTube video player” frameborder=”0″ allow=”accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” allowfullscreen></iframe>

Signs Of Moss Damage On Your Roof

If you can safely survey your entire roof, you can look for visual indications of mold growth. By noticing these signs early on, you can prevent further roof-related complications. 

The most common visual indicators of moss growth are:

  • Discoloration – Moss can leave green or brown stains on roofing materials.
  • Fuzzy textures – Roof moss can manifest as furry or spongy-looking growths resembling small vegetation patches.
  • Raised bumps – Sometimes, moss creates an elevated bumpy texture on your roof, making portions look like they are bubbling up.

Once you know what moss growth looks like, you should educate yourself on where to look for it. Although moss growth can occur on any portion of your roof, there are high-risk areas requiring frequent surveillance. 

The most noteworthy places moss growth occurs on roofs are:

  • Near debris buildups – Gutters, drain pipes, and warped portions of your roof can collect organic debris like leaves and dirt, facilitating moss growth.
  • Shaded areas – Portions of your roof with less sunlight, such as a section shaded by a tree’s shadow, can serve as a hotbed for moss growth.

Depending on the style, slope, and color of your roof, it may be easy for you to see whether you are experiencing moss growth. However, if portions of your roof are out of sight or too far away, it’s best to have a trained professional perform a thorough roof inspection so that you can prevent and treat moss damage.

How To Prevent & Treat Moss Damage

Every homeowner must know how to take care of roof moss to prolong their home’s life. Learn practical ways to prevent moss growth or to eliminate existing moss to keep your roof healthy for longer.


Although there are ways to treat established roof moss, you can implement prevention strategies to stop moss from growing in the first place, minimizing stress and expenses. The best ways to prevent the growth of roof moss are:

  • Regularly scheduled roof inspections led by qualified professionals
  • Keep your gutters clean to prevent debris buildup
  • Remove debris like piles of leaves off your roof
  • Trim nearby trees that are casting shade on your roof

Unfortunately, there is no such thing as an anti-moss shingle, meaning inspections and maintenance are the only efficient ways to keep moss off your roof. Hiring a roofing specialist is a great way to ensure you take the proper precautions to prevent moss growth. If your roofing team does find moss growth, they will also have the appropriate tools to remove it.


Treating moss growth on your roof can be challenging because simply cleaning the moss off isn’t enough to prevent regrowth. Jay Pscheidt, a plant pathologist with Oregon State University Extension Service, says that you will need to change the environment of your roof by letting “the sun in, or it will return.”

While it may seem tempting to try DIY moss removal techniques, hiring a professional roofing service to treat the moss on your roof is much safer and more effective. 

Some homeowners try using zinc sulfate to kill roof moss, but that method can hurt nearby ecosystems, cause health problems for the user, and hinder the roof’s appearance by leaving unsightly residue. Plus, climbing ladders and walking across roofs can be dangerous for untrained individuals.

Rely on qualified roofing specialists to remove the moss growth on the top of your home to guarantee optimal results and safety.

Stay On Top Of Moss Growth With Roof Life

Moss growth usually occurs on hard, moist surfaces shaded from the sun, including roofs. When left unchecked, moss can hold large amounts of water and displace shingles, leading to rot, mold growth, and the acceleration of roof deterioration. Due to the cool, wet climate, homes in the Pacific Northwest, especially in the greater Portland area, are particularly vulnerable to roof moss, putting those homes in danger.


To prevent the growth of roof moss, perform routine inspections and clear debris from your roof as needed. If you cannot confirm that your roof is moss-free, the experts at Roof Life of Oregon can assess it, treat existing moss, and help you safeguard it from future environmental threats.

Contact us today for a free roof inspection. We’ll perform a detailed check of your roof and provide you with a quote for moss removal or any other services you may need.

Previous Article
Next Article

Call Roof Life of Oregon Today

If you’re looking for a team that is as knowledgeable as they are kind and proactive, Roof Life of Oregon is the choice for you. Contact us today to experience the difference for yourself.

We’re Here to Help You

A healthy and properly functioning roof, free of moss and debris is also appealing and a source of homeowner pride.

Get a free quote for an inspection today.