How to Address Moss Growth on Roof Shingles

The presence of moss on shingle roofs can lead to various issues. While a thin layer of moss may not pose significant problems, larger clusters of moss can deteriorate shingles, penetrate beneath them, and create opportunities for leaks. Additionally, some widely recommended online methods for moss removal can potentially harm the shingles, increasing the risk of leaks. So, how can you safely eliminate moss from your roof? Should you remove moss before replacing the roof? And what measures can you take to prevent moss from regrowing after removal? In this guide, we will provide answers to these questions and offer insights into managing moss on your shingle roof.

Why Moss Is Detrimental to Shingles?

While some homeowners may find moss aesthetically pleasing on their roofs, it can be detrimental for several reasons:

Most plants acquire water from their roots, but mosses gather water from their leaves. Consequently, moss thrives on shingles, which are dry and relatively devoid of nutrients. Moss can develop roots that penetrate the shingles, potentially causing damage and creating openings for leaks.

When it rains, moss retains water, creating consistently damp conditions on your roof. Moss growth can also impede proper water drainage from the roof, as water must navigate around or through the moss rather than flow directly to the gutters. This prolonged exposure to moisture can lead to shingle deterioration.

Over time, moss can work its way beneath shingles, causing them to lift. This lifting creates opportunities for water to infiltrate lower layers of the roof and potentially your home.

While minor moss infestations may not immediately result in significant issues, they tend to worsen over time. Therefore, addressing moss growth promptly is advisable. In severe cases, damaged shingles may require replacement, and it’s best to consult USA Premier Roofing to assess the necessary intervention.

What If the Moss Appears Inactive?

In dry weather conditions, moss may appear to be dormant. However, certain moss species can remain viable even when desiccated for months. A single rainfall can revive the moss, causing it to resume growth. If you notice dormant moss, it’s a good opportunity to have a roofer remove it from your roof.

How to Remove Moss From a Roof

If your roof exhibits signs of moss infestation, it’s crucial to address the issue before it escalates. Moss is resilient, making manual removal by hand typically ineffective. However, you can employ a chemical solution to loosen the moss without causing harm to the shingles. We strongly discourage walking on the roof for moss removal. Here are the materials you’ll need and the steps to follow:

Materials Needed:

• A garbage bag.
• A garden hose.
• A ladder (prioritize ladder safety).
• A moss-specific cleaner certified by the EPA, without bleach.
• Alternatively, you can create your cleaner by mixing mild bleach or mild detergent with water in a spray bottle. A common mixture is 2 cups of chlorine bleach with 2 gallons of water or 8 ounces of dish soap with 2 gallons of water.

Moss Removal Steps:

1. Position your ladder securely near the moss-infested area. Using either your homemade cleaner or a store-bought option, spray the moss.
2. Follow the recommended duration for leaving the cleaner on the moss, as indicated on the store-bought product’s instructions. If using a homemade spray, allow it to sit for 15-20 minutes.
3. Using a garden hose set to low pressure, thoroughly rinse the moss. You should observe that most of the moss will wash away with the water spray. Ensure that the water doesn’t penetrate beneath the shingles or strike them forcefully to avoid causing damage or leaks. Even if the moss doesn’t come off easily, continue rinsing to remove all traces of the cleaner and prevent shingle damage.
4. Any remaining moss should now be sufficiently loosened for manual removal. While on the ladder, gently lift the moss from the shingles and deposit it in your garbage bag for proper disposal. You can secure the bag to your ladder to maintain stability.
5. If some moss proves stubborn and cannot be removed by hand, refrain from using other methods such as brushing or pressure washing, as they may harm the roof. Instead, consult USA Premier Roofing for guidance on the appropriate next steps.

Methods to Avoid for Moss Removal

Several methods for moss removal are not recommended, as they may damage the shingles in the process. It’s advised against attempting moss removal using the following techniques:

• Scrubbing: Scrubbing moss off shingles can damage the asphalt shingles and remove their granules, as moss strongly adheres to them.
• Pressure Washing: High-pressure washers can disrupt shingle adhesives, lift shingles, and strip them of their granule surface, potentially causing major leaks. Avoid using pressure washers or forceful water streams on your roof.
• Harsh Chemicals: High concentrations of bleach and other chemicals may cause permanent damage to shingles, increasing the risk of leaks.

Using such chemicals may also void your roof’s limited warranty. If you are uncertain about the safety or effectiveness of a moss removal method, consult USA Premier Roofing for guidance. Some roofers in moss-prone areas specialize in moss removal and can provide expert assistance.

Why You Shouldn’t Overlay a New Roof Over Moss

When considering a new roof installation, some homeowners may contemplate adding a second layer of shingles over the existing ones to save time and expenses associated with removing and disposing of the old shingles. While this approach can be convenient, it may not be advisable in certain situations.

For instance, if your roof has significant moss growth, covering it with new shingles without addressing the underlying issues is unwise. Several potential problems can arise if your roofer simply adds new shingles over your existing moss-covered roof, including:

• Uncertain Roof Condition: Severe moss growth may have compromised the quality of your existing roof decking and underlayment. The only way to assess their condition is to remove the shingles and inspect these layers. Failing to do so could jeopardize the performance of your new roof. Moss may not die immediately and could continue eroding the decking, increasing the risk of a roof collapse.
• Uneven Roof Surface: Damaged and swollen decking, combined with moss growth, can result in a new roof installation with an uneven surface. Bumps and depressions on the roof can disrupt proper water drainage and shingle sealing, potentially affecting your home’s curb appeal.
• Safety Concerns: Roofers need to walk on the old roof to install a new one over it, and moss-covered surfaces are unstable. Moss can shift beneath their feet, posing a fall hazard. While roofers wear personal fall arrest systems (PFAS) for safety, increasing the risk of a fall is unwise.
• Secondary Infections: When moss is deprived of sunlight, it will eventually die. However, the dead moss will remain on your roof, providing a source of water and nutrients for mold and fungi to thrive in dark conditions. If mold is left beneath your new roof, it can lead to secondary infections that spread into your attic, causing structural damage and affecting indoor air quality.
• Warranty Voidance: Adding new shingles over a moss-covered roof can void the limited warranty on the new roof due to the potential for damage.

Should You Remove Moss-Covered Shingles Before Installing a New Roof?

When considering a roof replacement, you may contemplate having roofers install the new roof over the existing one to save time and money. However, if your old roof is afflicted by moss growth, should you proceed with this method?

In certain cases, addressing the moss before a full roof replacement may be necessary. Your roofers may need to remove all the shingles from your old roof or clear the largest moss patches using a pressure washer before applying the new roof. This approach is advisable since the new roof will provide the necessary protection for your home, rendering concerns about the old roof’s condition irrelevant.

Benefits of Removing Moss-Covered Shingles Before a New Roof Installation

While you may not be required to remove moss-covered shingles before a new roof installation, it’s a course of action worth considering due to several advantages:

• Long-Term Cost Reduction: By removing the old roof, you preserve the option to add a second layer of shingles during future roof replacements. Most building codes typically allow a maximum of two layers of shingles on a roof. Therefore, if you proceed with this strategy, you will need to remove both roof layers during your next replacement.
• Home Value Preservation: If you plan to sell your home in the near future, a properly replaced roof is more likely to attract potential buyers, while a poorly replaced roof could negatively impact your home’s value.
• Risk Avoidance: By removing all moss-covered shingles, you eliminate the risks outlined earlier in this guide.

How to Prevent Moss on Your New Roof

After investing in a brand-new roof, it’s essential to take preventive measures to safeguard it from moss growth. Here are some ways to prevent moss from reoccurring:

• Eliminate Shade Sources: Moss thrives in shaded areas, so exposing more of your roof to sunlight can deter its growth. Consider trimming trees that cast shadows on your roof or relocating garden features like pergolas or trellises that contribute to shading.
• Install a Metal Strip: A copper, zinc, or galvanized metal strip installed along the roof ridge can deter moss, algae, and lichen growth. As the strip oxidizes over time and washes down the roof when it rains, it makes the roof less habitable for moss, algae, and lichen. This explains why you may notice a gap in algae or moss growth directly below your existing flashing or next to an aluminum-sided dormer. However, it’s important to note that a copper strip may take time to start inhibiting moss. It’s not a solution for an ongoing moss infestation but can help prevent future growth.
• Regular Inspections: Roofers can prevent moss growth by ensuring proper water drainage on your roof. They should conduct annual inspections and gutter cleanings to prevent water backups that could attract moss.

What If Moss Returns?

If moss reappears, avoid relying on harsh chemical treatments or dry spells to eliminate it. Chemical treatments may harm both moss and shingles, exacerbating the problem. Dead moss must still be manually removed to ensure proper water flow off the roof and to prevent issues like standing water and clogged gutters or leaks.

Need Assistance with Moss Management?

Whether you require the removal of a few moss-infested shingles or a complete roof replacement, reach out to USA Premier Roofing for a complimentary evaluation.