Moss on Your Roof: Causes, Risks, and How to Get Rid of It

Moss onYour Roof: Causes, Risks, and How to Get Rid of It

Introduction

What is Roof Moss and Why is It Common?

Roof moss is a plant that grows in moist and shady areas. Unlike most plants, moss lacks roots and instead uses rhizoids to absorb nutrients and moisture.  

How Moss Thrives in Certain Climates:

Moss is a highly adaptable and durable plant and can grow in most areas and conditions.  The only real requirement that moss needs to grow is for the environment to have enough water to be kept suitably damp.   Moss thrives in damp and shady conditions and does well in colder weather too which is a characteristic that separates moss from other plants. Moss has natural anti-freeze properties which help it thrive in the fall and winter seasons when other plants go into hibernation.  

Understanding how and why moss thrives on roof can help homeowners take preventative measures to protect their homes.

What Causes Moss to Grow on Your Roof?

Moss growing on your roof is typically caused by a combination of several factors:

Moisture and shades: If your roof doesn’t get enough sunlight or is regularly exposed to rain and shade, it will create the perfect environment for moss to thrive. Persistent dampness and limited sunlight, often caused by overhanging trees or nearby structures, create ideal conditions for moss growth.

Poor Ventilation: Inadequate roof ventilation can trap moisture, making it easier for moss to set up shop. Appropriate ventilation will help keep your roof dry.

Aging Shingles: Older roofing material can become permeable over time, providing an excellent surface for moss to latch onto.

Why is Moss a Problem for Your Roof?

Damage to Roofing Material: Moss can grow between shingles, eroding their protective coating, causing them to lift or crack, and ultimately compromising your roof's integrity.

Water Retention Leading to Leaks and Rot: If moss isn’t removed it can wreak havoc on your shingles as they eat away at their protective coating.  As stated above that moss can grow between shingles, this can prevent water drainage and result in mold growth, rot underlayment and damage framing.  Moss can also reduce your roofs ability to withstand UV exposure.

Compromised Aesthetics: Moss on your roof can significantly impact your home’s curb appeal.  While moss growth isn’t restricted to your roof, it can spread to other areas like sidewalks, driveways and patios making your whole home looking neglected and uninviting.  Additionally, the presence of moss can affect your homeowner’s insurance as insurance companies expect homeowners to maintain their properties to prevent avoidable damage.

Reduced Roof Lifespan: With the presence of moss on your roof, it can shorten the lifespan of your roof by trapping moisture and accelerate deterioration.

How to Remove Moss Safely and Effectively

DIY Moss Removal Methods

Using either a store-bought spray or a homemade one, spray the moss.  For store bought, follow instructions on how long to leave the solution on the moss. If you’re using a homemade spray, leave it for about 15-20 minutes.  Once your time is up, use your garden hose on low pressure to thoroughly rinse the moss.  Most of the moss should come off from the spray of the water.  Ensure to not direct any pressurized spray under the shingles as they might lift and create a leak.  Still rinse the moss thoroughly even if the moss isn’t coming off.  You could damage the shingles if all the cleaner that was sprayed on is not removed.  

Loosen any remaining moss and gently lift it off the shingles while standing on a ladder the avoid shingle damage.

Methods You Shouldn’t Use to Remove Moss

Scrubbing: While it may seem like a good idea, scrubbing can damage your asphalt shingles and remove their granules

Pressure Washing: Can strip the granules off your asphalt shingles which can wreck their performance and ruin their colour.  Even a small amount of pressure washing could cause problems including major leaks.

Using Harsh Chemicals: Using bleach or other harsh chemicals can cause permanent damage to your roof materials also increasing the risk for leaks.

Preventing Moss Growth on Your Roof

Regular Roof Maintenance: Clearing away sticks, leaves and other debris which all help moss grow, and frequently cleaning your gutter to prevent water buildup.  

Improving Sunlight Exposure: You can inhibit moss growth by allowing more sunlight exposure.  Trim overhanging trees to increase sunlight exposure and reduce roof moisture.

Installing Zinc or Copper Strips: GAF Master Flow® Zinc Moss & Mildew Preventer, can be installed near the ridge to protect your roof from the growth of moss, algae, and mildew.  Over time, the metal strip oxidizes, then as water washes over the roof plane, it will create an unsuitable environment for moss.

Choosing Moss-Resistant Roofing Materials: GAF HDZ and UHDZ ® shingles are designed to protect your roof as well as improve its appearance.  These shingles, built with StainGuard Plus®technology help resist the growth of moss and algae, allowing your roof to look cleaner for longer.  The StainGuard Plus®technology is a fancy feature in GAF shingles that are designed to prevent the growth of moss and algae.  The technology incorporates time-released algae-fighting copper elements into the shingles surface.   The time-released formula ensures a longer-lasting and more reliable defense for algae growth.  StainGuard Plus® helps to maintain your roofs overall appearance and reduce the maintenance needs over time.

How Moss Affects Different Roof Types

Asphalt Shingles: Moss traps moisture against asphalt shingles, keeping them damp for extended periods. Over time, this weakens the shingles, creates an ideal environment for mold and algae growth, and can cause the shingles to lift, making them more vulnerable to wind and water damage.

Wood Shake Roofs: Wood shake roofs are particularly prone to moss growth because cedar naturally absorbs rain and precipitation, creating a perpetually damp surface. Moss can accelerate wood decay and shorten the roof’s lifespan significantly.  

While wood shake roofs are highly susceptible to moss due to their organic composition, tile roofs face their own unique challenges when moss takes hold.

Tile Roofs: Moss on tile roofs can make the tiles more porous, increasing the likelihood of rainwater seeping through. This becomes especially problematic during freezing temperatures, as expanding ice can crack or burst the tiles. When the ice thaws, tiles may shift or pull apart, leaving gaps that lead to leaks. Additionally, the rhizoids that moss uses to anchor itself can create cracks in tiles, further exacerbating water damage.

Unlike wood and tile roofs, metal roofs are more resistant to moisture but are not entirely immune to the effects of moss.

Metal Roofs:  Although metal roofs are strong and durable, moss can still cause issues by anchoring itself to organic debris that accumulates on the surface, such as pollen, leaves, or bird droppings. The trapped moisture can accelerate corrosion over time, diminishing the roof’s longevity and appearance. Regular cleaning and maintenance are essential to prevent moss from taking root on a metal roof.

The Long-Term Benefits of Moss-Free Roofing

Improved Curb Appeal and Home Value: Regular maintenance and moss-free roof helps your home look clean and well maintained, increasing your home’s curb appeal and can contribute to your homes resale value.

Prolonged Roof Lifespan: As moss-free roofs are less prone to moisture, loss of granules and weakening of your roof structure extending the life of your roof.

Saving Money on Repairs and Replacements: Without moss, your shingles will maintain integrity and stay securely in place minimizing the risk of water infiltration and subsequent damage to your home.  This will also eliminate the need for frequent repairs saving you money over time.

Healthier Indoor Environment: Preventing and avoiding moss growth reduces the chances of mold and mildew spreading into your attic or other interior spaces, providing a healthier living environment.  Additionally, a clean roof reflects sunlight more effectively which will regulate indoor temperature and help reduce energy costs for heating and cooling.

Conclusion: Protect Your Roof, Protect Your Home
Moss growth on your roof is more than just a cosmetic issue—it poses serious risks to the integrity of your home. From damaging shingles to creating an environment for leaks and mold, moss can lead to costly repairs and a shorter roof lifespan. By understanding the causes and dangers of moss and implementing the proper removal and prevention methods, you can safeguard your roof for years to come.

Regular maintenance, thoughtful upgrades like moss-resistant shingles or zinc strips, and strategic landscaping adjustments can make a significant difference in keeping your roof moss-free. At North OKGN Construction, we’re here to help you maintain a safe, durable, and attractive roof!

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