Is It Bad to Have Moss on Your Roof? | Pro Answers & Tips

August 16, 2021

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Is it bad to have moss on your roof? Believe it or not, some people love moss. Unlike mold, moss is a plant that doesn’t produce spores or poisons, so it is relatively harmless. In Japan, moss grows quite frequently, with over 2,500 of the 12,000 known species of moss growing in their country alone. Moss is essential to Japanese culture, so much so that it is mentioned in their national anthem. It is often seen in gardens and is admired as a lovely plant within their culture. Although moss may be admirable in Japanese culture, it has a bad reputation in western culture, mainly when it grows on the rooftops of homes. While moss may have an admirable aesthetic quality in gardens, this beautiful plant can be very destructive when it grows on homes.

Is it bad to have moss on your roof? Yes. Moss and other organisms growing on the roof can cause significant damages to systems. Routine professional power washing services will prevent extensive problems from moss and algae growth.

Although moss seems like patches of harmless green growths on top of a roof, the prevalence of moss can slowly erode the wood on your roof. Eventually, it can lead to leaks that can be rather costly to repair. After all, moss is a living organism and needs to attach its roots to something to keep it growing and thriving. So, as this seemingly innocent plant takes root in your shingles, it can be the beginning of a moisture problem for your roof. Or it could be a sign that a moisture problem has already been present for some time.  

moss growing on roof bad before power washing

Either way, seeing algae on your roof is not a good thing, no matter how beautiful or admirable this plant may seem. However, if you see moss along with its cousins, algae, and lichen, then it’s time for you to call out the experts to clean your roof. Left unchecked, moss, algae, and lichen can cause considerable damage to your roof.   

What Makes Microorganisms Grow on The Roof 

Roofs seem like a very aerated place. It’s up high, exposed to the sun, the wind, the rain, and other elements. So, it is surprising that it can come under attack by living organisms. But unfortunately, it does. Some roofs are safe in these elements. As long as the homeowner properly maintains the roof, it won’t become a haven for microorganisms to thrive. Here is why these growths tend to grow on your roof.  

Moss & Lichen

Moss and lichen love cool, damp, shady areas. If your home is right in the middle of a sunny area, then problems with moss and lichen may hardly ever be a problem for you. However, if your home is surrounded by shade from trees or other buildings, then you likely experience moss and lichen problems often. Moss is a green, flowerless plant that looks like a carpet, while lichen is a white, crusty organism. 

roof cleaning service

If moss or algae is present, then it is likely that lichen will be present, too. They all grow together in a symbiotic relationship. Sometimes, it isn’t typical for moss to grow over your entire roof. Instead, they tend to like the area that the sun doesn’t frequent. So, if the front of your home gets a fair share of sunlight; you may not even be aware that microorganisms are growing on the back, shaded part of your house. As a result, you may have a massive problem on your hand that can be resolved if you keep your roof cleaned regularly.


  • Even though moss and lichen are bad to have on your roof, the good thing about them is that they are colorful. So, you can easily recognize that you have this problem by seeing green and white colors scattered all over your roof. Algae is a problem that may not be as apparent until it’s too late, particularly if you have a dark-colored roof.  

When you think of algae, you probably think of the green-colored algae that you see in ponds. So, you may not even realize that you have an algae problem because you don’t see green stuff on your roof. Besides, the green stuff is typically moss. The algae that may be present on your roof is a devious type of algae because it often is the same color as dark-colored roofs. This black-colored microorganism on your roof is known as Gloeocapsa magma which appears black but is a blue-green alga.  

Some homeowners often dismiss these algae as stains. In fact, it is a living organism that is just as destructive as moss and lichen. Gloeocapsa magma is attracted to roofs with limestone such as asphalt shingles.    

Should I Remove Moss and Algae From My Roof? 

The answer to this is a resounding “yes.” The sooner you get these organisms off of your roof, the better. As a homeowner, you may not be able to see these things growing on your roof. This may be because you don’t know how to spot them as a roof cleaner or a roofing contractor can. Or it may be because the algae and the moss may be growing on a portion of the roof that you can’t see. If you live in a heavily shaded area, these problems may be prevalent. This is why it is a good idea to have your roof cleaned at least every two years. However, if you are in a moisture-rich area where your home hardly gets enough sunlight during the day, then it would be a better idea to get your roof cleaned once a year. 

power washing moss and algae off the roof

You can expect to pay on average $300 to $600 to have your roof cleaned. Depending on where you live, this rate may be much higher or lower. If you have problems with moss, algae, or lichen, this may drive up the costs. This range may seem steep, but it is a small price to pay compared to roof repairs or roof replacement. Roof repairs can be in the thousands, whole roof replacement can cost you tens of thousands of dollars. 

Why Moss and Algae are Bad For Your Roof 

These microorganisms seem harmless but, they are very bad for your roof. This is because they slowly erode your shingles by eating away at them. For instance, Gloeocapsa magma feeds on asphalt shingles. Moss takes root in your shingles and starts growing, which can cause shingles to break away from the decking underneath the shingles. This leaves an opening for rain and moisture to get into the roof’s sheathing. Both of these organisms can cause the following problems.

  • Wood Rot

This is a common problem, mainly when moss is present on your roof. Once the moss burrows into your shingles, the shingles expose the wood underneath to air and moisture, which can start rotting your wood decking. Gloeocapsa magma can cause sheathing to rot, too. However, its destructive process is slightly different from moss. Instead of its growth causing shingles to detach, the algae eats away at them, causing them to curl, warp, or break, exposing the sheathing to water and air.    

  • Leaks

Whether you have a problem with moss, algae, or both, deteriorating decking will inevitably lead to leaks. It may take a very long time for you to realize that you have a leak. You will know when you start to see brown or yellow-colored stains on your ceiling. However, by the time you begin to see visible problems, the damage to the decking may be so bad that you will have to have your roof repaired. If the damage is excessive, then you may have to have your entire roof replaced.  

Am I Protected By Insurance if Moss Damages My Roof? 

If you are a homeowner and you experience roof leaks, you may be able to get some relief from your home insurance provider that can offset the charges for your roof repairs. However, many factors go into determining whether your home insurance will cover roof damages.  

expert power washing

Damages that homeowners’ insurance typically covers are damaged caused by a fallen tree, hail damage, or fire. You will be surprised to know that your homeowner’s insurance may not cover roof leaks if it is not associated with these perils. If an adjuster inspects your roof due to an open claim and discovers that you have been negligent in maintaining your roof, your roof repairs may not be covered by insurance. Negligence includes not having your roof inspected and, most importantly, allowing for things like moss and algae to accumulate on it.  

Another thing that could put you in a bind is if you have a roof that hasn’t been maintained and gets damaged by the previously mentioned perils. You may have difficulty collecting on your claim even if your policy covers the peril because you failed to maintain the roof before the peril happened. Even though this is a tricky situation, you may end up having to be responsible for the roof damages. Not keeping your roof clean can have a domino effect of negative results leading to many expensive repairs. Are you still thinking that cleaning your roof is too expensive?

How Can I Get Moss and Algae Off of My Roof 

You can get moss off your roof yourself. However, the dangers of cleaning a roof are substantial so, it’s a good idea to have a cleaning company do it. For one thing, the pitch of your roof may be dangerous. This, coupled with a slippery environment on your roof from water and chemicals or detergents, can cause you to fall. Professional roof cleaners typically have the type of equipment necessary to avoid slipping off a roof. Another reason you should leave the cleaning to experts is because even if you are careful not to fall, you could still damage the shingles on the roof by walking around on the system.

professional roof cleaning and power washing

A cleaning company may address your moss problem by using a broom to help loosen it from your shingles. After this, if you have plants surrounding your home, they will need to water them well so that the chemicals they use to remove the algae or moss from your roof will not destroy the plant life. Various cleaning companies will use a variety of cleaning tools and products. One of these tools may be a low-pressure washer. Along with this washer, the cleaning crew may use a diluted solution of bleach. Or they may use another type of commercial cleaner. These chemicals may be highly toxic, or they may be eco-friendly.  

After cleaning your roof, the algae may immediately disappear. You will notice the difference because your roof will be visibly lighter than before. Moss may take some time to completely disappear, however. This is because when moss grows on your roof, it anchors itself into your roof with its roots. So, when a roof cleaner washes the roof with chemicals, some of it will start to come off, but it takes a few days for the chemical to obliterate the moss. Once the remaining moss dies, the wind and rain will carry it away. 

What Are Some Ways To Keep Moss and Algae Off My Roof 

Moss, algae, and lichen are a part of nature, so they aren’t going to go away forever. An excellent way to keep them at bay is to ensure that you are getting regularly scheduled roof cleanings. It would be best if you had your roof cleaned once a year but certainly no longer than every two years. If moss, lichen, and algae are consistent problems, you may want to increase the frequency of cleanings. However, if the thought of you paying to have a cleaning crew come out and clean your roof several times a year isn’t in your budget, then you can resort to a few other options that can keep moss and algae off your roof.

  • Paint the Roof

One of the best ways to resolve the moss and algae issue is to paint your roof. This can keep moss at bay for longer than a bare roof and keep you from having to get frequent cleanings. Some top-notch paint brands produce paints that are mold, moss, and mildew resistant. These paints can range from $22 to as much as $150, and this can double, triple, or quadruple depending on the amount of paint needed. While painting a roof can be pricey too, at least you won’t have to deal with the moss or algae problem as often. Another benefit of painting your roof is that if you use a lighter paint color that is UV resistant, it may save you on your energy bills by creating a “cool roof.”

  • Use Zinc or Copper

Another solution you can consider is having zinc or copper strips installed on your roof. The droplets react with the metal and release molecules onto your roof that keeps moss from growing when it rains. While your roof will still need regular cleanings, this can keep the algae and moss problem under control until your next cleaning. 


power washing moss growing on roof

Moss, algae, and lichen will continue to accumulate on roofs. But you don’t have to deal with the damaging effects of these organisms if you keep your roof cleaned regularly. Cleaning your roof can be a substantial investment, but it is far cheaper than roof repair or replacement. Consider having your roof cleaned by Largo Pressure Washing Services to protect your home from unnecessary repairs and damage. They not only specialize in keeping dirt and grime off your roof but can also keep moss, algae, lichen, and other unsightly gunk off your roof. 

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