What causes lichen on roof

What Causes Lichen On Roofs? [It’s Worse Than You Thought]

When clean, roofs can add a ton of value to a home. Not only is your roof critical for safety, but it doesn’t hurt to have a good-looking one.

Unfortunately, most homeowners seem to neglect their roofs until it’s too late. That leaves a ton of time for some pretty destructive organisms to grow on your roof.

This is why, among other reasons, it’s extremely important to get frequent roof cleaning services to preserve the life of your roof.

In this case, we’re going to talk about one of the most damaging organisms, Lichen. Lichen does not always develop on pavements, sidewalks, patios, and wood flooring. It could also develop on your roof and cause water leakage if left unchecked.

But, what causes lichen on roofs?

Well, it’s a combination of algae and fungus growth- but it’s preventable if you get ahead of it.

If you decide to ignore your Lichen problem, you’re going to have some roof damage that isn’t as simple as replacing a couple of shingles or tiles. Get ahead of it, before it gets ahead of you.

We’ll be looking into what causes lichen on the roof, how to prevent regrowth, and how to get rid of them in this article.

What Causes Lichen On Your Roof?

Straight to the point- lichen is caused by algae and fungus reproducing with each other, forming lichen. Algae and fungus end up on your roof from wind debris, nearby trees that drop material on your roof, and any other kind of organic material that ends up on your roof.

Is Lichen Bad For Your Roof?

Yep, the longer it stays on your roof, the more time it has to develop “roots” onto your roof. Over time, it actually latches onto your roofing material and will damage your roof whenever you try to wash it off.

What Is Lichen On Roof?

what causes lichen on roof
Lichen On Roof Shingles

Lichen is an invading species created by the combination of fungi and algae. The significant element of lichen is a fungus, as well as a fungus that depends on algae for nutrition that enable it to expand and flourish. To develop, lichen needs sunlight, moisture, oxygen, and nutrition.

Lichen can take on a variety of sizes and forms. They come in a variety of patterns such as blue, green, white, black, grey, yellow, orange, red, and brown.

yellow lichen on roof
Yellow Lichen On Roof

Lichen is categorized into 3 kinds: foliose, fruticose, and crustose. Foliose lichens have 2 different upper and bottom surfaces. They might be plain, bushy, or curved.

Fruticose lichens can be formed like corals or bushes, having round or smooth branching. Most fruticose lichen colonies are void in the center, whereas others develop out from the center. Crustose lichens are clusters that create a shell over a material.

What Causes Lichen on Roof? 

As I mentioned earlier, Lichen comes from the “mating” of algae and fungus. Preventing Lichen, or understanding where it comes from involves understanding and preventing the growth origin of algae and Fungi on your roof.

In general, algae is the most common growth you’ll find on your roof- it’s pretty non-invasive, and can be cleaned. Algae colonies, or “seeds” are called spores, and these spores end up on your roof as they through the air from any kind of organic debris.

So, it doesn’t matter where exactly it came from- but it came from some other algae growth that got picked up by the air and fell on your roof. Considering how fast algae reproduces, one spore is enough to cover your entire roof.

So, long-story-short, Lichen ends up on your roof over time as algae and fungus grow on your roof from organic debris that fell on your roof. Usually, that means that some algae or fungus was picked up by the wind and carried all the way to your roof (unfortunately).

Why Lichen is the most damaging roof growth.

Lichen traps humidity against structures, accelerating regular wear and tear.

When surface moisture froze in cool weather, it can cause frosty damage to roof shingles and other outside materials. It can cause your rooftop tiles to flex, distort, and even break from one another over the period.

The problem with Lichen is that while they usually take the longest to show up, they have the strongest grip on your roof.


These little guys might not have roots, but they sure find a way to stick to your roof. A lot of times, especially if allowed to grow unchecked, cleaning these lichens involves cleaning them with bleach solutions and soft-washing them away. However, they usually grab onto the protective layers of your roof (especially with asphalt shingles), so when they come off, they take those layers with them- leaving holes behind.

Yep, if you don’t keep your lichen in check, they can actually cause holes in your roof. Pretty crazy.

Fortunately, they don’t require as much water to survive as moss does, so it doesn’t cause as much high-moisture damage as moss would, but it can definitely still cause moisture damage over time.

It should go without saying, but if you think you might have some kind of algae, fungus, or lichen growing on your roof, you need to get take care of it before it becomes a bigger problem.

As with most things in life, prevention is much more effective and reliable than treatment will ever be.

Don’t let it go to the point where you need to repair your roof- just take care of the problem, or hire a professional to take care of it for you!

How To Prevent Lichen on Roof

Metal or copper strips across the top of your roofs could help destroy lichen and keep it from growing again. Houses with metals at the top of their roof appear to be less susceptible to lichens.

The fundamental reason is that the metallic composition, when coupled with rainfall, appears to induce a chemical process that damages the lichens while also cleaning the roof. It can also be used to reinforce an old roof.

However, if you’re not interested in installing a metal roof, or installing metal or copper strips across your roof, then the only way to prevent lichen is to make sure that you’re constantly cleaning your roof.

Don’t allow algae or fungus to grow- and you won’t have a problem.

How to Remove Lichen From Roof

Lichen can be extremely difficult to remove due to its tenacious hold on the surfaces. If you try to clean it with a hand tool, you could accidentally destroy the protecting upper surface of your roofing shingles as well.

Power Washing

You could power wash your roofs as long as you take caution not to harm the shingles. If somehow roofing shingles are aged and more brittle, you may cause unnecessary roof leakage when some of the lichen cracks or drops away.

Also, if you’re interested in learning about 3 key reasons you should pressure wash your roof, check out this article!

If you choose to power wash your roof to eliminate lichens or mosses, use the appropriate tools and a moderate chemical instead of a harsh abrasion cleaner. You can then carefully wipe the dislodged lichen and algae from the rooftop. If you are still unsure, it is best to contact a roofing company that has the necessary professional expertise and abilities to complete the work for you.

If you decide to replace your old roof with a new one, The majority of modern shingles come with pesticides that finally destroy and prevent roof lichens, mildew, and fungus from sprouting.

Removing Lichens (General Notes)

Now that we’ve answered the first question- What causes lichen on roof? We can move on to dealing with the next step- prevention.

It is not recommended to climb on your rooftop and wipe or rinse them away. Except if you are confident that your roof is strong, stable, and structurally sound enough just to support your body weight. Dry scraping and industrial cleaners and pesticides are used to get rid of the lichen from the roofs.

But keep in consideration that you may also be damaging the roof shingles with chemicals. If your roof is entirely and almost fully covered in mosses, algae, or lichens, you should likely have your entire house re-roofed. You may acquire better removal agents that are designed exclusively for asphalt roofs and will destroy the lichens.

The Bottom Line- Don’t wait! 

If you haven’t gotten the theme of this article by now, then let me make it crystal clear.

Don’t wait before the algae, fungus, or lichen becomes a problem. Once it’s a problem, then you have a PROBLEM to solve. If you get ahead of the problem, then you’re going to prevent any headaches that might be associated with removing developed fungus, algae, or lichen.

Professional assistance has always been a great way to guarantee that your roof is clear from lichen and other sorts of invasive organisms.

If you’re located in Miami, and you’re interested in having someone inspect your roof for any kind of bacterial growth- then give Picazzo Painting a call. We’ve treated a number of roofs around Miami for algae, and can quickly identify the extent of the growth on your roof.

We’ll also be very transparent- if the growth is developed beyond the point where a simple pressure cleaning can solve it, we’ll let you know.

However, don’t let it get to that point- get ahead of your lichen problem.

Get A Free Lichen Inspection

If you’re interested in a free, comprehensive roof inspection for any kind of bacterial growth, call (305) 796-2443 today!

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2 responses to “What Causes Lichen On Roofs? [It’s Worse Than You Thought]”

  1. Your suggestion of metal strips on the roof might keep the Lichen off the roof. Well I’ve just cleaned my roof with a high pressure unit, after I’d sprayed and killed the lichen with bleach, that was growing on a Colourbond metal roof. It’s a fairly big roof and the whole roof was covered except for the side facing west and included the guttering and the ridge capping.
    Now my plan is to each year spray the roof with bleach and hope it prevents it from growing again. Is that the way you would go or am I on the wrong track ?

  2. Why you so dramatic re: lichen? You say the roof needs to be re-roofed if covered in lichen, but then you have pictures of a roof before and after with the former being covered in lichen. Fuck off you pieces of twat.

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