How To Remove Moss From Your Roof

Moss can spring up between shingles on roofs in damp climates or under thick tree cover. Some people may find the look of a moss covered roof picturesque, but over time, moss can cause roofing materials to degrade because it traps moisture which may cause damage to decking and joists. To extend your roof’s life span and put off the cost of a new roof as long as possible, you should remove moss as soon as you identify it. We’ll walk you through the moss removal process step-by-step and show you how to keep it from coming back.

 

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Identifying Moss on Your Roof

Moss is a type of dense plant growth that is most prevalent in damp or shady areas. It frequently grows on tree-shaded or north-facing roof surfaces where moisture isn’t able to drain away or evaporate. Roof moss is generally green and can be found between and beneath shingle tabs.

 

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Understanding Moss Growth

Moss is a small, rootless plant that grows in sheets. It reproduces using spores that are spread through the air and water. Two factors contribute to moss buildup on roofs: water and organic debris. Together they nourish the plant and encourage it to spread. That’s why you usually find moss growing on roofs in shaded areas where water isn’t able to evaporate quickly.

Although some think moss growth on a shingle roof creates a charming, cottage-like appearance, it actually damages asphalt shingles and other roofing materials. Over time, moss buildup widens fissures and gaps in these materials and traps moisture against the roof. In gutters and downspouts, moss can create blockages, sending water over the gutter edges and down to pool by the home’s foundation, potentially causing water damage. Because it spreads quickly, it’s important to clean moss away as soon as you find it.

 

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Preparing for Moss Removal

Before you start the process of roof moss removal, you’ll need to gather your tools and materials and take a few safety precautions. Most homeowners probably have the tools needed to combat a moss problem on hand. It’s worth noting that we recommend using the low pressure of a garden hose—rather than a pressure washer. Pressure washing may remove moss, but it will also damage shingles. The pressure blasts away granules and weakens roofing materials. You’re better off using a hose and a soft-bristled scrub brush than a pressure washer.

Tool	Cost Range*
Garden hose	$20–$50
Goggles	$10–$15
Ladder	$80–$160
Long-handled scrub brush	$10–$20
Plasting sheeting	$7–$20
Safety harness kit (optional)	$100–$150
Soft-bristled scrub brush	$8–$27
Spray bottle (optional)	$6–$15
Spray nozzle	$8–$16
Work gloves	$5–$10

*Costs via Amazon.

You’ll need some kind of cleaning solution, which you can make or buy. Commercial pre-mixed moss killer is available as both a dry powder and a liquid. You can mix your own solution by combining 1 to 3 cups of chlorine bleach, a bit of dish soap, and 2 gallons of water. Keep in mind that bleach is deadly to most plants, so you’ll need to cover nearby bushes and flower beds with plastic sheeting.

Finally, it’s important to take ladder and roof safety seriously. It’s difficult to properly apply the chemical solution without getting up on the roof, which means that there’s a fall risk. If you plan to spend significant time on your roof, you can purchase a personal fall arrest kit that includes a harness, safety rope, and roof anchor.

 

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Step-by-Step Guide to Removing Moss

Follow these steps to clean moss from your roof.

Step 1: Safety Measures

• Moss removal is best done when the weather is warm but cloudy. Direct sunlight can cause cleaning solutions to evaporate before they have time to kill moss.
• Wear old clothes and non-slip shoes. Put your supplies in a bag or a backpack so you can keep both hands free for climbing on and off the roof.
• Set up your extension ladder on level ground with the base of the ladder about 3 feet away from the roof’s edge. If your ladder won’t attach to the roof, have another adult hold the sides when you climb up and down.
• If you’re using a roof safety kit, follow the manufacturer’s instructions to anchor the brackets to the roof and attach the rope to the harness.

Step 2: Initial Cleaning

• Using your hose’s spray nozzle, spray loose moss off the roof, starting at the peak and moving downward.
• With a long-handled brush, gently scrub to remove the bulk of the moss. Move slowly and carefully, since a wet roof can be slippery.
• Rinse away debris.
• Consult the manufacturer’s instructions on your moss-killing solution—you may need to wait for the roof to dry to apply it.

Step 3: Applying Moss Removal Solutions

• Wear rubber gloves and goggles for protection against moss spores and chemical moss killers.
• If you’re using a powdered moss killer, apply it in horizontal lines parallel to the roof’s edge. The lines should be spaced about 2 to 4 feet apart. Some of these powders need rainfall to be activated and distributed, so apply them when rain is forecasted.
• If you’re using a liquid moss killer, you’ll typically use either a pump sprayer or a bottle that attaches directly to a hose. Working from the top down, apply the solution to small sections at a time to ensure you cover the entire surface.
• If you’re using a homemade bleach solution, put it in a spray bottle or pump sprayer, working from the top down in small sections.

Step 4: Removing the Remaining Moss

This step is particularly important. Even when dead, moss can trap moisture on your roof and lead to other types of damage.

• Bleach solutions and liquid moss killers usually need to sit for at least 20 to 45 minutes to work. The more severe the moss problem, the longer you should leave it on.
• For dry powders and some long-acting liquids, you may need to wait for a few weeks before returning to your roof to remove the dead moss. Consult the manufacturer’s instructions.
• When the appropriate amount of time has passed, carefully climb back on the roof and use your scrub brush to loosen and remove the remaining moss. You can use a scraper or utility knife for stubborn patches, but take care not to damage roofing materials.
• When you’re finished, rinse the roof again. If you’ve used bleach, you may want to hose down nearby plants. Even if they were covered by plastic sheeting, they could have received some of the solution runoff.

Step 5: Post-Cleaning Roof Inspection

• Allow your roof to fully dry, and then perform a visual inspection to ensure you’ve removed all the moss.
• If some moss remains, repeat the above steps until the roof is completely clean.

 

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Professional vs. DIY Moss Removal

In many cases, this is a home improvement job you can handle yourself. Moss removal requires only basic tools, and the cleaning solutions typically cost less than $50. The biggest issue here is safety. Roof work already comes with a fall risk, and working on a wet, moss-slick roof is even riskier. Carefully consider whether doing it yourself is worth the money you’ll save.

Typically, professional roof cleaning costs between $0.20 and $0.30 per square foot for moss removal, which is about $300 to $450 for a 1,500-square-foot roof. Obviously, this is substantially more expensive than doing it yourself, but professional cleaners can probably get the job done quicker and more thoroughly than you can. They’ll also know how to avoid damaging roofing materials. If you don’t already have the right equipment or you don’t fancy the thought of climbing on your roof, consider calling in pros.

 

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Preventing Future Moss Growth

Once you’ve thoroughly cleaned your roof, do your best to keep it clean with the following tips.

• To directly prevent moss growth, you can install a treated metal strip near the top of any roof surface prone to developing moss. Most moss removal solutions contain zinc, so installing zinc strips will turn precipitation running down your roof into a constant moss killer.
• Trim back any tree branches overhanging your roof.
• As soon as you notice any roof damage, hire a professional roofer to fix the problem. Roof repair expenses are generally worth the investment to prevent further damage.
• If your roof is more than five years old, have it inspected annually to catch potential problems before they cause serious damage.
• If it’s nearing time to replace your roof anyway, consider installing metal roofing materials. These are a bigger investment than asphalt shingles but have greater energy efficiency and it’s less likely for moss, mold, or mildew to develop on it.
• Keep your gutters clean and in good repair. Gutter cleaning costs and gutter repair costs are substantially lower than the cost of replacing a roof or repairing a damaged foundation.
• Additionally, installing high-quality gutter guards can reduce the frequency with which you need to clean them.

 

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Our Recommendation

Moss growth on a roof damages the shingles and other materials, which shortens a roof’s life span. This can potentially expose your home to structural damage over time. Shingle roof installation costs are high, so it’s worth it to take care of a moss problem as soon as you can. Moss removal is something you can do yourself, but it does entail a safety risk, so hiring professional cleaners may be a better option. Once you’ve removed the moss, we highly recommend taking steps to prevent it from growing back in the future. This includes keeping up with all roof maintenance tasks.

 

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