How to remove moss from your roof and keep it from returning

Key points

• Moss loves moist, dark environments — reducing these elements around your roof prevents moss buildup.

• Moss removal methods include DIY cleaning solutions that contain baking soda and citrus oil.

• Maintaining your roof, gutters and nearby trees can keep moss from growing and spreading.

Moss has its perks, such as better soil diversity and helping your garden’s ecosystem.  Even though moss, lichen and algae can indicate good air quality, you don’t want them growing on your roof shingles.

This furry green organism can wreak havoc on your shelter and possibly expedite the need for a new roof. That’s because moss gets cozy between the roof’s shingles, filling the space with moisture. Eventually, the shingles will lift or warp, causing leaks and water damage.

You want to tackle this problem sooner than later to avoid paying the full cost of a new roof.

Before you scale a ladder and remove the moss yourself, consider whether your efforts will be effective in the long run. This is one home improvement project that can benefit from the experience of professional roofing services.

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What does it mean when moss grows on your roof?

Roof moss can materialize for several reasons, but the main one is consistent dampness. You should expect moss growth, especially if you live in an area without consistent sunshine. 

Even roofs in sunny states such as Florida can harbor moss if a tree canopy covers the house. 

“A well-shaded roof prevents the evaporation of moisture, creating excellent conditions for moss to continue to grow,” said Andrew Prchal, cofounder of Gunner Roofing in Stamford, Connecticut.

Here are a few reasons moss can grow on your roof:

• Moisture: Moss loves a wet, moist environment. But moss doesn’t need gallons of water to thrive. “When moss grows on your roof, it indicates moisture retention on the roof surface,” said Aaron Brilliant, owner of Emerald Roofing and Siding in Baltimore, Maryland.
• Lack of sunlight: Moss doesn’t like sunlight. “Moss, lichens, and algae reproduce in moist environments, especially in north-facing or shaded roof areas where sunlight is minimal,” Brilliant said.
• Presence of spores: Moss is already outside, living on trees and damp ground. But if you have trees covered in moss close to your home, it’s possible for the moss spores released to replicate, land on your roof and launch a new habitat, Prchal explained.

How do you get rid of moss on a roof?

There are several methods to deal with moss. However, these can change depending on the material of your roof. Your first step for roof moss removal is to identify your home’s roof material.

Asphalt shingles

Asphalt shingles can typically handle chemical treatments and gentle removal by hand. First, “use a chemical solution to loosen the moss without damaging the shingles,” said Prchal. 

Liquid moss killer products can be found at your local hardware store or on Amazon. Brilliant recommended skipping products with zinc and potassium salts of fatty acids, as they can be toxic to aquatic life. “If you must use them, disconnect downspouts during application to prevent runoff into waterways, he said.

An alternate cleaning solution uses baking soda and citrus oil-based products. “Baking soda alters the pH, making the environment unsuitable for moss,” Brilliant said. Prchal suggested a mixture of water and vinegar.

Spray the treatment onto your roof with a garden hose attachment. Then, gently remove the remaining moss clumps or dead moss with a wire scrub brush.

Since this home improvement project requires climbing a ladder, use nonslip shoes and rubber gloves. A safety harness or safety rope is a good idea if your house is very tall.

But above all, don’t use a pressure washer on asphalt shingles. It can damage shingles, stripping granules (a protective layer added to asphalt roofs), and water can make its way behind the shingle, Prchal said.

Clay shingles

Given clay’s hard surface, it may be harder for moss to build up on terra cotta roofs. If you find that moss does adhere to your clay shingles, approach the removal process as you would for asphalt shingles: spray the roof with a moss removal solution, then gently scrub off the residue, Brilliant recommended.

Wood shingles

For a roof with cedar shingles, gently scrape off the moss in small sections. Clean the surface with a diluted bleach solution. You want to apply it by spraying and letting the cleaning solution sit for 10–20 minutes. This step should kill the remaining mold and mildew and soften any stuck-on grime. Rinse and repeat the steps as necessary.

Metal shingles

Like clay shingles, metal shingles are less likely to see moss buildup. Since it’s a durable surface, you can try to pressure wash the cleaning solution off using a low-pressure setting. To ensure you don’t damage your roof, test a small portion of the roof first.

How do you prevent moss from growing back on your roof?

There are a few ways to prevent moss growth on your roof. These typically include removing shade sources but can also mean picking the right shingle from the start.

To reduce shade, trim tree branches hanging above your roof. This will allow your roof to get more sunlight and expedite moisture evaporation after rain and snowfall. “Sunlight is the best defendant in stopping moss growth on your roof,” Prchal said.

Failed efforts to combat moss growth might have something to do with your roof material. Consider roof replacement that suits your home’s surroundings and environment. “Installing zinc strips, copper strips or galvanized metal strips on your roof in areas that do not get direct sunlight can help reduce moss, algae and lichen growth,” Prchal said.

These materials work well against moss because roof water runoff makes it harder for moss to grow.

What’s next?

You will need professional remediation if your house looks like something out of The Hobbit. Contact a roofing expert for a full evaluation. The moss removal course of action depends on the extent of the moss coverage.

Ask your roofer about how you can deal with small patches and discuss preventative measures to keep moss from spreading. For example, clean moss buildup from your gutters and ensure they drain properly. “Water backup will cause growth,” Prchal added. “This will help you avoid any pricey roof repair in the future.”

And, of course, continue routine roof maintenance and roof cleaning.