How To Remove Moss From Your Roof

A step-by-step guide for roof moss treatment and why you need to eliminate it

Removing moss from the roof with a bristled brush

The Spruce / Jayme Burrows

Project Overview
  • Working Time: 8 - 12 hrs
  • Total Time: 2 - 4 days
  • Skill Level: Intermediate
  • Estimated Cost: $50 to $150

Lush, thick moss on a roof may look quaint and picturesque, giving the home a fairy tale, hobbit-like feel, but it can seriously damage your home. Moss crowds the shingles, leading to decay and leaks, and destroys a roof to the point of needing replacement. The best roof moss treatments have two stages: Apply a chemical treatment in either powder or liquid form, then physically scrape away the dead moss. Never skip the last step since soggy, dead moss can spread decay and worsen the roof problem.

What Is Moss?

Moss is a non-vascular plant that needs direct contact with water to live and thrive. It doesn't flower or put down roots; instead, it is spread by spores and water.

How Moss Ruins a Roof

Once moss finds a habitable roof spot, with a steady source of moisture out of the sun, moss begins to form as a thin dusting of green. It spreads by spores in the air, expanding to other similar areas, becoming wider, thicker, and mat-like.

The moss grows in the seams between shingles, thickening with growth, filling with water like a sponge, and raising shingles. Water absorbed by the moss finds its way under the shingles, onto the roofing felt, and permeates the roof's structure. A neglected roof full of moss can collapse in a few months.

Which Roofs Are Most Susceptible to Moss?

North-facing roofs generally receive the least sunlight and are prone to moss, especially when the climate is cool and damp. Moss grows best in highly shady areas, such as under heavy tree canopies. Moss needs a constant water source to grow; however, the sun speeds up water evaporation in sunny spots, removing the dampness.

Wooden shingles are porous and the most vulnerable, promoting rotting faster than other shingle types. Physically scraping moss from a wooden roof is often more difficult than metal, composite, or asphalt shingles.

Before You Begin

Moss-killing products are generally grouped into two main types: dry powder and liquid. Dry moss killers are cheaper, more cost-effective, and have a longer shelf life but are considerably more labor intensive.

Powdered or Granulated Moss Killer

Dry powder moss killers are applied by sprinkling the powder in multiple lines parallel to the house's ridge, spacing the lines about 2 to 4 feet apart. When it rains, the water mixes with the powder and runs toward the eaves. After about a week, the moss should be dead.

Dry powder moss killers require that you go onto the roof and take stock of the moss problem during application. You can determine the problem's extent by physically being on the roof and planning the following removal process.

But dry moss killers can be difficult to dispense evenly, and they can leave white streaks that sometimes remain on the roof until several hard rain showers wash them away. And if a strong wind comes along before the rain, the dry powder can blow off before it can work on the moss.

Liquid Moss Killer

Liquid moss killer comes in a container that attaches to a garden hose and is blended in as the water flows. Liquid moss killers cover the roof more evenly than dry powders, letting you stay on the ground for the application. If the water spray doesn't reach the roof's peak from the ground, you can spray while standing on a ladder. While the application can be easier than a powder version, you will still need to mount the roof later to remove the dead moss.

Because it can be difficult to keep track of your progress when spraying the roof, it helps to mentally section out portions of the roof and spray each section before moving on to the next one. It also helps to start with a dry roof.

Moss killer works at any time of the year but is typically applied in the early fall when sunlight diminishes and moss develops. Moss removal must occur after the moss is fully dead, which can take a month or two.

Warning

Most commercial moss killers are made with zinc. Some communities may have restrictions about flushing zinc into stormwater discharge areas. Check with your local water quality agency about zinc runoff restrictions. A homemade alternative to commercial moss killer is a bleach and water solution or vinegar and water solution.

Safety Considerations

If doing this project yourself, you must climb onto the roof to apply the powder, or if you use liquid, you will still need to remove the dead moss. This is dangerous work, especially if your roof is high or has a steep pitch. Before tackling this project, ensure you are confident about working on a roof or tall extension ladders. In most cases, it will require that you place an extension ladder against the house and climb up.

For high or steep roofs, secure yourself with a harness before climbing onto the roof to apply moss killer. Roof harnesses include brackets secured to the roof, with straps designed to arrest your fall should you slip while working on the roof. Roof harnesses can be rented at home improvement centers and tool rental outlets, but investing in a harness kit (about $100) might be a good idea if you expect to have regular roof work projects.

If you are unsure of your skills or nervous about heights, hire a professional service.

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What You'll Need

Equipment / Tools

  • Roof harness (optional)
  • Tall extension ladder
  • Garden hose (optional)
  • Putty knife or painter's 5-in-1 tool
  • Long-handled, soft-bristle scrub brush
  • Applicator spoon, scooper, or trowel (for dry moss killer)

Materials

  • Moss killer

Instructions

Materials needed for removing moss from the roof

The Spruce / Jayme Burrows

How to Remove Moss From Your Roof

  1. Apply the Moss Killer

    • Dry powder moss killer is best applied when a slow, steady rainfall is predicted in the weather forecast. Dispense the moss killer in uninterrupted horizontal lines about 2 to 4 feet apart, parallel to the roof ridge. Use a spoon, scooper, or hand trowel, depending on the size of the moss problem.
    • Wet moss killer works best when a garden hose is attached to the container. Run the water until the moss killer flows out and spray the roof, beginning at the ridge and working downward. You may need several bottles of moss killer for expansive roofs.
    Applying dry moss killer powder to the roof

    The Spruce / Jayme Burrows

  2. Wait for Rain (Dry Moss Killer Only)

    Dry powder moss killer is activated and dispersed by precipitation. Light rain on the roof will cause the moss killer to flow downward and cover all roof areas. If there's no rain in the forecast, lightly spray the roof with water to mimic rainfall, spreading the powder over the roof.

    Allowing the dry moss killer to sit

    The Spruce / Jayme Burrows

  3. Remove the Dead Moss

    When all the moss has turned visibly brown, it is dead and can be removed. This can take a month or more after application of the moss killer. This slow, steady process may take several days if your roof is large. Pace yourself and take breaks whenever you become tired.

    • Climb the roof and remove the moss, working from the bottom up. The best tools are a long-handled, soft-bristle scrub brush, a putty knife, or a 5-in-1 painter's tool. Use these tools to lift moss mats and gently brush them away.
    • In the seams, use the sharp edge of the scraper like a dental pick to force out the moss.
    • Work from the eave line up to the roof ridge, carefully brushing away loose moss as you go (loose moss can pose a slipping hazard).
    • If there are multiple roof planes with moss, repeat the same process with each section, starting at the bottom and working up.

    Warning

    Remove moss only when in dry conditions. Never work on a wet roof, which can be slippery.

    Removing moss with a scraping tool

    The Spruce / Jayme Burrows

  4. Rinse Off the Roof

    • Spray down the roof to move the moss debris down to the gutters. This step allows you to see what areas you still have to work on.
    • Don't resume your work until the roof is completely dry.
    Rinsing off the roof after moss removal

    The Spruce / Jayme Burrows

FAQ
  • How do I prevent moss from growing back on my roof?

    The best way to prevent moss growth is to cut back plants or whatever gives shade to the roof.

  • Can you use a pressure washer to remove moss?

    You can use a pressure washer to remove moss from a roof, but it's not recommended because it can damage or loosen shingles.

  • How much is roof moss treatment and is it worth it?

    Hiring a professional to clean your roof, factoring in moss removal treatment, can cost $500 to $1,000. To do it yourself would cost under $100 for the supplies. If you notice moss growth on your roof, it is worth the time and money to remove it, whether on your own or with an expert.

  • How long does roof moss treatment last?

    Moss removal treatment usually lasts two to three years. However, if you live in a damp location with much tree cover and not much sun exposure, you might need to repeat moss removal treatment efforts every year.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Moss in the landscape. University of Maryland Extension.

  2. How much does it cost to clean a roof? Angi.