How To Remove Roof Moss

Moss on your roof is more than just an eyesore. If you let it grow, it can cause serious damage to your roof by lifting shingles, leading to leaks and shortening your roof’s lifespan. Luckily, there’s a simple fix that many homeowners can tackle with the right tools. In our article, we’ll tell you how to remove roof moss and prevent it from coming back.

For visual guidance, you can watch our video featuring This Old House’s general contractor Tom Silva as he uses zinc strips and a cleaning solution to eliminate roof moss and lichen on a roof.

Why Moss Grows on Roofs

Roof moss is a common problem, especially in areas with high humidity or frequent rainfall. Moss doesn’t have roots—it absorbs water and nutrients directly through its leaves, so it can easily grow in many locations. There are several factors that make a roof a common place for moss growth, including: 

• Debris: Leaves, twigs, and other organic matter that land on your roof provide nutrients for moss.
• Moisture: Moss loves damp environments, so if your roof doesn’t dry quickly or get a lot of sunlight, it may accumulate. 
• Shade: Trees or other structures that cast shadows on your roof keep the area cool and damp, which is the perfect breeding ground for moss.

The Dangers of Roof Moss

Here are a few ways moss can wreak havoc on your roof:

• Aesthetic issues: Moss affects your curb appeal by creating dark streaks and patches on your roof.
• Moisture retention: The plant acts like a sponge and can hold moisture against your roof’s surface.
• Reduced lifespan: Since moss puts physical stress on your roof, it can significantly shorten your roof’s lifespan.
• Shingle damage: As moss grows, it can lift and separate shingles, which is where water can enter your home. 

Removing Existing Moss

There are preventive measures to stop moss from growing on your roof, but you have to remove existing plants first. You can use a combination of physical removal and chemical treatment.

Preparing for Moss Removal

Since this project requires roof work, you must take the proper precautions. You can leave it to the professionals if you aren’t comfortable on a ladder or roof, but if you’re ready to take the do-it-yourself (DIY) approach, follow these tips:

• Choose a dry day with mild temperatures to remove the moss.
• Cover nearby plants and grass with plastic tarps to avoid getting the cleaning solution on them. 
• Use a sturdy ladder and have someone spot you for safety.
• Wear non-slip shoes and protective gear, including gloves and safety glasses.

Physical Removal Techniques

Below are the steps to physically remove the moss:

1. Use a soft-bristled brush or broom to gently sweep away loose moss.
2. Work from the top of the roof down to avoid lifting the shingles.
3. Apply gentle pressure to the shingles to avoid damaging them.

Chemical Treatment

Now that you’ve physically removed as much as you could, kill the remaining moss with a cleaning solution:

1. Mix equal parts bleach and water in a garden sprayer.
2. Apply the solution generously to the moss on your roof.
3. Allow the solution to sit for 15–20 minutes.
4. Rinse thoroughly with clean water from a hose, working from the top down.

As you can see in the video, Silva emphasizes just how important it is to protect the surrounding vegetation because bleach will harm plants. He also avoids damaging the roof by taking special care and only spraying affected areas.  

Preventing Future Moss Growth

After you’ve removed the existing moss, you can start taking preventive measures so that it doesn’t return. The first line of defense against moss on a roof is zinc strips. These strips release zinc particles when it rains, which disrupts moss growth. We’ve shared the instructions to install zinc strips below and included some other options to create an environment inhospitable to moss growth.

Installing Zinc Strips

Here’s how to install them:

1. Slide a margin trowel under the shingles to loosen them from the ones below.
2. Insert the zinc strip underneath the loosened shingles and bring it up to the stop.
3. Secure the strip with hot-dip galvanized roofing nails. You can use the pre-drilled holes.
4. Apply a dab of tri-polymer sealant to each nail head for added protection.
5. Run a bead of sealant under each shingle to refasten the tabs.
6. Continue installing strips across the length of the roof, and be sure to leave a 1/8-inch gap between strips for expansion.

One row of zinc strips near the ridge is enough for most roofs, but you may need a second row halfway down the slope if you have a large roof.

Additional Prevention Methods

Zinc strips are highly effective, but we have a few more ideas to share with you below:

• Clean gutters regularly so there isn’t water backup and moisture accumulation.
• Install copper or zinc-coated ridge caps.
• Trim overhanging branches to increase sunlight exposure.

Maintaining a Moss-Free Roof

Regular maintenance will help you keep your roof moss-free through bi-annual inspections and ongoing care.

Regular Inspections

Perform roof inspections at least twice a year, ideally in spring and fall:

• Look for damaged or missing shingles that could allow moisture penetration.
• Check the flashing around chimneys, vents, and other roof penetrations for signs of wear or damage.
• Keep an eye out for any signs of new moss growth.
• Make sure gutters and downspouts are clear and work properly.

Ongoing Care

To maintain a healthy, moss-free roof:

• Address any roof repairs immediately so that you can avoid water from entering your home.
• Check that you have proper attic ventilation to reduce moisture buildup.
• Consider professional roof cleaning every few years, especially if you live in a damp climate.
• Keep your roof clean by removing debris regularly.

When To Call a Professional To Remove Moss from a Roof

This is a straightforward DIY project that many homeowners can take on themselves, but there are times when you may need a professional roofer’s help. They have the experience, equipment, and knowledge to safely and effectively remove moss. Here are a few situations in which you might want to hire a roofer to remove moss:

• Concerns about using chemicals or damaging the roof
• Extensive moss growth or damage to the roof structure
• Lack of proper safety equipment or physical ability to perform the task
• Steep or high roofs that pose safety risks

Cost Considerations

As with any home improvement project, you have to take your budget into consideration before diving in. We’ve broken down the cost associated with installing zinc strip on your roof below:

Material Costs

As mentioned earlier, you will need to first remove moss before installing zinc strips and taking other preventive measures. To apply your cleaning solution, you need bleach, water, and a garden sprayer. A jug of bleach costs about $5 and a garden sprayer is approximately $10.*

After you’ve removed the bleach, you can apply your zinc strips. Prices vary depending on the brand and quality, but on average, they cost $30–$50 for a 50-foot roll. Keep in mind that if you decide to hire a professional, they will charge you a fee on top of material costs for their labor and expertise.

*Cost data in this article sourced from Angi.

Maintenance Expenses

While you may not need to perform maintenance immediately, we’ve covered the cost of gutter cleaning and roof inspections below:

• Regular gutter cleaning: The average cost of gutter cleaning is $167
• Roof inspections: It costs $235 on average for professional roof inspections

Budgeting Tips

There are a few ways you can manage the costs of roof moss removal and prevention:

• Compare prices from multiple suppliers for materials.
• Obtain estimates from several roofing professionals before committing to a service.
• Consider DIY moss removal for smaller roofs to save on labor costs.

Remember that the prices may be steep to remove moss from your roof and prevent it from returning, but you’ll save in the long term because you won’t need to prematurely replace your roof or repair shingles.

Tools