How to Remove Lichen From Roof Tiles and Outdoor Surfaces

How to Remove Lichen From Roof Tiles and Outdoor Surfaces

There’s nothing to like about lichen. Especially when it invades on your home’s outdoor surfaces. This ugly growth spreads across roofs, walls and sidewalks with strands or “fingers” holding on with a powerful grip. Here’s the lowdown on lichen and how to kick it to the curb with Wet & Forget Outdoor.

What is lichen?

Lichen is a combination of an algae and a fungus. It can be found growing on roofs, pavers, rock walls, grave stones, sidewalks, outdoor cushions and other outdoor surfaces. Lichen is an invasive organism and may appear on surfaces as tiny, shrubby branches (fruticose) leafy structures (foliose), or in crusty patches (crustose). Lichens thrive on a combination of sunlight, carbon dioxide, water and minerals.

What are the most common types of lichen?

One of the mostly commonly seen types of lichen is made up of a single-celled green algae (Trebouxia). This type of lichen is found growing worldwide in temperate, alpine and arctic regions worldwide. Lichen can grow in a wide range of temperatures and conditions; from the hottest desert to the coldest arctic tundra.

What does lichen look like?

Lichens comes in multiple shapes, sizes and forms including shrubby, leaf-like or crusty. It may appear as an orange crust on a rock wall, or as mint green patches on a roof. Lichen can be seen in a variety of colors including blue-green, gray, brown and yellow.

lichen on stone

Is it harmful? Should I remove it?

While lichen may appear to be harmless it can cause significant damage to outdoor surfaces over time. Lichen holds moisture against the surface; speeding up wear and tear. This can shorten the life of your roof or other outdoor surfaces.

This surface moisture may freeze in cold weather which can cause frost damage to asphalt shingles or other surfaces. As time goes on, your roof shingles may bend and warp. The lichen can penetrate your roof’s exterior causing the shingles to separate. This spells disaster for your roof!

Another reason to remove lichen growth is your homeowners insurance rates may increase. Your insurance company may send out an inspector to drive by your home to observe any changes. If the inspector sees a dirty, lichen-covered roof this may give them a reason to raise your rates or even cancel your policy. Over time, lichen can cause serious damage. Fortunately it can easily be removed with Wet & Forget Outdoor.

lichen roof

How do I get rid of lichen?

The problem with scraping, sweeping and raking-

Removing lichen with a brush, broom or scraper is one common way to remove it. Unfortunately, removing lichen this way is very time and labor intensive. Lichen is known to hold on tight with a tough grip. If you attempt to remove it with a hand tool you may accidentally remove the protective top layer of your roof shingles as well.

Using metal strips

Lichen avoids galvanized steel, copper and zinc because these metals work as a natural biocide. Adding metal strips along your roof’s ridge line may inhibit lichen growth. When rainwater moistens the strips a tiny amount of metal will run down on your roof preventing the lichen from grabbing hold. Unfortunately, copper and zinc dripping from your roof is bad for the environment. The runoff will find its way into streams and ponds where it is toxic to fish and other wildlife. Metal-infused rainwater is also unsuitable for landscape use.

Chlorine bleach

Removing lichen from your roof with chlorine bleach may seem like an economical solution but the end result may be corroded downspouts, gutters and flashings. True to its name, chlorine bleach may “bleach” your asphalt shingles, lightening or changing the color. Bleach solution that drips from your roof during or after application can kill landscape plants and ruin outdoor fabrics. You may need to wear protective clothing when apply bleach as the solution can burn the skin. The bottom line is bleach can be hazardous to people and the environment.


Using a high pressure washing system to remove lichen is not recommended as it can degrade your roof’s protective coating. In addition, your home’s outdoor surfaces aren’t built to endure the effects of water applied with high pressure. Seals around windows and doors may be compromised. Skylights and roof windows may become damaged. Water that is forced underneath your home’s siding can get into the inner walls causing mold growth. FYI- Some shingle manufacturers will void the warranty on their products if they discover that you have subjected your roof to high pressure washing.

lichen on wood
Why is Wet & Forget Outdoor the Best Way to Remove Lichen?

Wet & Forget Outdoor’s gentle, eco-friendly formula kills lichen without damaging your outdoor surfaces.

To thoroughly treat and eliminate lichen two applications of the product is required. Wet & Forget Outdoor works with the wind and rain to remove unsightly lichen; just spray it on and you’re done! And Wet & Forget Outdoor keeps on working to keep outdoor surfaces clean and lichen-free for months!

How to Apply Wet & Forget Outdoor

Dilute 1 part Wet & Forget Outdoor to 5 parts water and apply with a garden sprayer.

To make one gallon of solution:

Add 2 1/2 cups (20 oz.) of Wet & Forget Outdoor to your garden sprayer. Add water to your garden sprayer’s one gallon mark.

To make two gallons of solution:

Add 5 cups (40 oz.) of Wet & Forget Outdoor to your garden sprayer. Add water to your garden sprayer’s two gallon mark.

Listen to this unsolicited testimonial from Dave L. -left on Wet & Forget’s corporate voicemail:


wet forget cleaner headstones

Treating Lichen and Moss

To get rid of lichen thoroughly saturate the surface with the Wet & Forget solution. Wait 15 minutes. Repeat application a second time. This will allow the product to deeply penetrate the growth. It’s best to do this on an cool, overcast day to minimize evaporation.

Surface Preparation

For best results apply Wet & Forget Outdoor to a dry surface. A cool, dry morning with no rain in the forecast is ideal. Remove any loose debris from the surface before spraying. Completely saturate the surface with Wet & Forget Outdoor to penetrate the growth.

Ideal Temperatures for Application

 Outdoor temperatures should be above 32°F (0°C) during application and for the next 4 to 5 hours after application.

Ideal Weather

For best results apply Wet & Forget Outdoor on a cool, dry day. This will ensure that the surface will remain wet for an extended period of time. This gives the product optimum time to do its job.

Future Maintenance

 After the stains and growth has disappeared use Wet & Forget Outdoor as a routine maintenance tool to keep your surfaces clean and lichen-free. Once a year or so reapply the product at the first sign of new growth.

Cleaning Vertical or Covered Surfaces

Vertical surfaces or surfaces without exposure to the elements like covered porches and headstones may require some assistance with a hose or a scrub brush. If the area is heavily stained a yearly application of Wet & Forget Outdoor will keep surfaces clean.

Eliminating lichen is easy with Wet & Forget Outdoor. No labor-intensive hand raking or scraping is required. Don’t let a lovely summer day be ruined by disgustingly dirty outdoor surfaces. Wet & Forget Outdoor will make your outdoor living areas shine like new!


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  1. Jacquie coble

    Can this product be used on the sand in a childs sandBox? If so how should i apply it?

    1. Wet And Forget

      Hi Jacquie,
      Wet & Forget can be used on the sandbox but we wouldn’t recommend applying to the sand. I would follow the directions on the bottle for children’s play equipment.

  2. Scott jenkins

    Can Wet And Forget be used on cedar shake shingles?

    1. Wet And Forget

      Hi Scott,
      Absolutely! Wet & Forget is safe and effective for cleaning cedar shake shingles. For best results, apply a good heavy amount to the surface and then just allow the wind and the rain to do the cleaning for you.

  3. Debbie Edgar

    Will Wet And Forget remove calcium deposits on pool tile and moss rock?

    1. Wet And Forget

      Hi Debbie,
      Wet & Forget will remove the moss on your rocks, but it won’t clean calcium deposits on pool tiles.

  4. Brent

    I have grayish colored lichens on a painted metal roof on older house trailer-cottage. Can I use this product safely on the white painted steel roof and the white painted sides. Roof is most likely galvanized steel while sides are most likely aluminum.

    1. Wet And Forget

      Hi Brent,
      You can definitely use Wet & Forget to take care of the lichen that is on your painted metal roof. Wet & Forget is safe to use on all types of roofs including both painted and metal surfaces.

  5. Terry A Johnston

    You seem to discourage the use of a high pressure washer, but would it be okay to use Wet And Forget in a high pressure washer using a wide angle nozzle? There is no way I can apply to my chimney or roof with a garden pump sprayer.

    1. Wet And Forget

      Hi Terry,
      You can use Wet & Forget with a pressure washer, but you must be able to pull from a larger premixed tank, rather than using water from a hose connected to your home. A pressure washer will not properly mix Wet & Forget, so pulling from a premixed tank is the only workaround. You can also use a Trombone Sprayer to apply Wet & Forget from a large distance away.

  6. Kevin Carney

    My shingles are weathered grey. Will wet and forget change the weathered grey look of the shingle like bleach or would it stay a weathered grey color?

    1. Wet and Forget

      Hi Kevin,
      Our product will not change the weathered grey look of your shingles. Wet & Forget does not contain any bleach and will not harm the weathered grey color of your shingles.

  7. Fiona Cole

    Can you use wet and forget on a clear polycarboante pergola roof?/

    1. Wet and Forget

      Hi Fiona,
      Wet & Forget is safe to use on a clear polycarbonate pergola roof.

  8. gavin

    Can this be used with lead lettering on a marble gravestone? Not sure if it will react with the lead and stain the stone?

    1. Wet And Forget

      Hi Gavin, Wet & Forget is perfectly safe to use on marble gravestones that have lead lettering. No need to worry about any damage to the stone.

  9. Bob m

    Can wet and Forget be used on an IPE wood deck with cedar rails? Should I pressure wash first to remove some algae and lichen growth?

    1. Wet And Forget

      Hi Bob, Definitely use Wet & Forget on your IPE wood deck and cedar rails. I would apply Wet & Forget first and leave it. If you don’t want to wait on the rain and you would like to speed up the process, feel free to pressure wash about a week later.

  10. Al

    Can Wet and Forget be used with success to remove without scrubbing lichen from asbestos siding ?

    1. Wet and Forget

      Hi Al,

      Yes, you can use Wet & Forget to remove lichen that is on your asbestos siding without scrubbing. However, there is a second step that you need to follow when applying to surfaces that have lichen on it. After you apply the Wet & Forget to the surface, wait 15 minutes and then apply a second time.