How to Remove Lichen From Roof Tiles and Outdoor Surfaces

Wet & Forget
by Wet & Forget
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.
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.
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.
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.
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