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How to Remove Algae and Moss from Your Roof

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We all want our homes to look well-maintained. Even if a house was built decades ago, we still want it to be attention-grabbing. But one part that commonly betrays the age and condition of any home is the roof.

Have you ever experienced looking up at your roof, only to discover some ghastly black streaks or greenery that ruin the overall appearance of your home? Are they dirt? Are they debris? Or are they something else that you should worry about? But whatever they may be, they make your home look old, unkempt, and dirty.

More often than not, you are dealing with algae and moss on your roof in this kind of situation. Don’t fret, it is not black mold and you won’t have to replace your roof immediately. That is unless of course the algae and moss growth have become unmanageable.

What Are These Algae and Moss on the Roof?

You might wonder how is it possible to for algae to be present up on your roof, if you believe they only appear on land or water. This is a pretty common misconception because the algae that is present on the roof is a different type from the one we are most familiar with.r

Algae is a collective term for microorganisms that depend on photosynthesis to survive. It is not necessary for them to be submerged in water – as long as they get the necessities for photosynthesis, it does not really matter where they are.

While the moss on the roof also requires photosynthesis for survival, it is different from algae. Algae are microorganisms with nonvascular systems that allow them to absorb nutrients by themselves, while moss are considered plants and have vascular systems and use their roots to get nutrients from other sources.


Taking a Closer Look at Algae Growth

The algae that grows on the roof is the blue-green algae known as the Gloeocapsa Magma, and these cyanobacteria do not just appear out of nowhere. They start as cell clusters or spores that have been blown off and end up on your roof. They thrive best in places with high humidity, and when they do, which usually takes months, you will normally see them on the north side of your roof where sun exposure is less and the moisture is plentiful.

These single-celled organisms are also capable of producing a sheath that protects them from the UV rays coming from the sun, allowing them to retain moisture. Roof algae rapidly multiply and produce spores that will also be blown off to other places, like the roof of nearby homes where they can also grow and thrive.

Even if you have gotten rid of the algae on your roof but there is algal growth on the roof of other nearby homes, chances are you will have face the issue repeatedly.

Having algae on the roof is something that occurs to a lot of households. Fortunately, this is also a problem that can be easily remedied.

Moss on Your Roof: How Did This Happen?

If you discovered that algae are present on your roof, chances are you also have moss growing alongside it. If not, you can expect it to eventually make an appearance if you do not immediately do anything to address the presence of algae.

Algae and moss usually come together because they require the same type of environment. That is, they both need shade and moisture. And like algae, they end up on your roof via spores that travelled through air, and will also grow in the same conditions. Also, even animals that pass by your roof can bring those moss spores with them.

But unlike algae, moss can grow and reproduce anywhere on your roof. They do favor the north side of the roof where there is less sun as well, and this is why moss tends to grow a lot in that area. Moss also act like as a sponge that retain water and this can cause a lot of damage to your shingles and even other components of your roof.

Why Algae Needs to be Removed from the Roof

Fortunately, algae on your roof is considered as more of an annoyance than something that can cause damage, particularly at its early stages. It is only when it has been left alone for a long period of time that it may affect your roof. Also, it is said that it is not the algae itself that can cause the most harm, but how it lets moisture stay on the roof. This moisture is what damages your roof.

But even if algae do not seem to cause your home any harm, aside from being an eyesore, it is still better to get them removed to be on the safe side. Issues on your roof can be costly to address in general, and it is better for you to get them resolved sooner than later.

These shingles make use of limestone fillers that give it weight, and algae love to feed on lime. This constant feeding may weaken the shingles on your roof and cause cracks to appear.

You might worry about their presence if you have solar panels installed on your roof. Because these panels need to be placed where sunlight is abundant, which is something that algae hate, these cyanobacteria will not be attracted to go to that area and make a home out of it. Your panels are safe.

Left alone, algae can lump together with fungus on your roof and when this happens, lichen is produced. This lichen has roots that are attracted to the granules of shingles and will eat away at them, as well as wrap themselves around it. Lichens cannot be removed that easily once they start growing on your roof.

The case is different for shingles and shakes that are made out of cedar. It is said that algae present on this type of roof will also cause moss to grow, which is more destructive. The moss will feed on the cedar, causing it to rot. When this happens, the solution that most professionals do is a replacement of the damaged sections, if not the entire roof.

Did you know that algae on the roof can also affect your home’s insurance coverage? If you had insured your home, you know that inspectors are required to check on the condition of your home. If they see those algae streaks on your roof, they can use it as a reason to jack up the price of your insurance, or even cancel it altogether.

Luckily, removing algae on the roof is not that difficult. It normally just involves using chemicals that contain bleach. If you feel that the algae on your roof is still fresh or at the early stages, you can do the cleaning yourself. But always remember, safety first!

For DIY cleaning, you only need to combine equal amounts of water and bleach and use a water sprayer that uses low pressure. Allow the bleach and water solution to sit on your roof for around fifteen minutes before washing it off with just plain old water. Make sure that the bleach and water solution will not dry off because it be harder for you to rinse it all off once dry.

But if you feel that the algae growth on your roof is quite bad or you are not confident to do the cleanup yourself, getting a roofing contractor to do the job is the wisest choice. A lot of algal growth on the roof would require stronger chemicals that only professionals should use.

To give you an idea, here are the chemicals often used to remove algae on the roof and why it is best to let the professionals handle them:

  • Lye or – although this is much more environment-friendly compared to bleach, this chemical is still considered toxic. In fact, anyone is at risk of getting burns with direct skin contact with it Not only that, it can even cause your roofing nails to melt and the asphalt shingles to get damaged. That’s how strong it is.
  • Oxygenated bleach or Sodium Percarbonate – often in powder form, this is a combination of soda ash and hydrogen peroxide. Although it is not risky to handle, it should be left up on the roof for almost an hour and must be kept wet at all times. This means staying up on the roof for around 45 minutes and keeping the oxygenated bleach wet by constantly watering it. Are you willing to do that?
  • Chlorine Bleach – though an inexpensive option, bleach is known to cause discoloration to most of what it comes into contact with, including roof shingles. Not only that, bleach can also help speed up metal corrosion, affecting your downspouts, , , and the metal roof itself. It is also known to be toxic to the environment, so exercising care is important when using it.

Using this also has the side effect of algae growing back and becoming worse than before. Instead of removing them, the bleach will just camouflage the algae. And when this happens, the spores that have recently arrived will feed on the algae and grow thicker than the one they fed on.

  • Trisodium Phosphate or TSP and dishwashing powders in the past, this compound is also useful in removing algae on the roof. Because it can stain the wood and cause damage to the paint and metal of your roof, caution is needed when using this. It can also affect the landscaping of any home because it is known to cause harm to the environment and its runoff can flow to the plants below it and possibly kill them.

Other methods can also be used to rid your roof of algae, as well as prevent them from using your roof as their breeding ground. These include:

  • Using a pressure washer – while this is one of the easiest methods to remove algae on the roof, this is also a quick way for your roof to get damaged. High pressure washers can ruin the protective layer of your shingles that block your roof from too much exposure to UV rays.

Not only that, using high pressure washers to hose down algae can even damage the windows and skylights up on your roof, as well as the seals used to prevent water leaks. This is why only a low-pressure washer should be used.

roof being pressure washed

  • Installing metal sheets – if you recall, we mentioned how algae reacts badly to certain metals. In particular, , , and galvanized steel can be considered as algae killers. These metals act as protective barriers that prevent algae from settling on the roof. They also combine with the rainwater runoff, which then affects the algae already present.

However, metal is bad for the environment. Even just small amounts of zinc and copper can already cause much damage, especially when it reaches bodies of water where aquatic life are present; these metals are toxic to them. Recycling rainwater from your roof to use as water for gardening may also not be possible because the runoff will contain traces of these metals.

The presence of algae on your roof does not mean you already have to entirely replace it, contrary to what others might say. But when they make an appearance on your roof, you can expect to see them again even after getting them removed. Roof algae does not really go away, even if you use one or two of the methods we mentioned above.

Once algae start making a home out of your roof, they will still reappear later on. However, this does not mean you should just leave them alone. Doing so may cause problems to your roof later on, especially when they start feeding on the lime on your shingles. Algae can also promote the growth of lichens and moss on your roof as well, and these two are the ones that can cause the most damage, not the algae.

Getting Rid of Moss on Your Roof

If you look at it, you might feel that having moss on your roof actually brings character to your entire house. It might even seem like your house came straight out of a storybook and this might make you hesitant to remove it. Why get rid of something that looks like a great addition to your home?

Like in the case of roof algae, the presence of moss on your roof can also affect your home’s insurance coverage.

But unlike algae, moss itself can cause damage. This is because they develop roots that can hold water and may go deep into your shingles. Weather changes can cause the water stored by moss to thaw and freeze repeatedly. This action will cause the shingles to crack or even separate.

When shingles of the roof are damaged or have detached, water will easily penetrate your roof. This can cause rotting of the wooden components and the only way to fix it would be to replace not just those rotted parts but also sections of your roof as well, if not your entire roof. What a costly solution!

If you recall, algae on the roof can be removed through several methods. But how about moss?

The methods of removing algae apply as well for moss on your roof. Most contractors would also use scrub brushes to sweep moss away from the roof, especially if the growth is caught early.

Fortunately, there are measures you can take to help prevent or minimize their reappearance, such as:

  • Getting metal sheets installed at the top and sides of your roof
  • Cutting off tree branches so that the sunlight will reach all parts of your roof
  • Making sure that the roof is free of debris that can hold moisture in place
  • Using roof shingles that are resistant to algae, especially if you are considering a replacement.

Do note that these measures apply not just to moss but also to algae growth prevention.

Dangers of a Potential Roof Leak

Whenever your roof gets damaged, the most common consequence of it is getting leaks. And if you have ever experienced leaks, you have an idea of how troublesome they can get.

Dripping sounds at the dead of night. Getting your stuff wet. Leaving water marks on your beautifully polished floors or pristine carpets. Having to faceplant because you did not see the puddle of water on the floor. If you have leaks at home, you need to be prepared to experience these things. Fun, right?

Anytime you suspect that the roof is the source of a leak you discovered, you need to get it resolved at the soonest possible time. There are so many issues that leaks can cause, especially if you leave it alone for so long.

It’s not just being constantly annoyed by these leaks that you have to deal with, but you may also have to face the following issues:

  • Wood rot – like we mentioned, too much water exposure will cause wood to rot. Even the sturdiest wood is no match for this, and most roofs do make use of wood components. It can be the or , shingles, shakes, or something else, and these parts are often the first to be affected by leaks. If not addressed, don’t be surprised if your roof suddenly collapses. Any kind of structural issue, including rot, is dangerous.
  • Damage to your attic or ceiling, especially those that are present for a long time, will eventually lead to attic and ceiling leaks. And when this happens, it can cause all sorts of issues as well, such as stains and paint or plaster bubbles, that can spread out to the walls in the immediate vicinity. Even your stuff can also get water damage from these leaks.
  • Accidents – it is an unfortunately common occurrence for people to get into accidents caused by leaks, including those coming from a damaged roof, that may result in broken limbs. You may have even got into one yourself because of a slippery floor. With roof leaks, slippery floors are guaranteed, unless you place buckets to catch all the water.
  • Poor insulation leading to increased consumption of utilities and higher bills – roof leaks are signs that your roof may have cracks, holes, or gaps that water passes through. Did you know that it also affects your home’s insulation, because it will require you to turn up your heating even more during cold days and make your air conditioner run cooler than you normally do when it gets hot?
  • Fire – a basic science lesson that we are all aware of is that water and electricity mixing together is a disaster waiting to happen. If water leaks reach your electrical wirings, short circuits may happen and these can easily .
  • Growth of mold and mildew – mold and mildew, especially the dreaded black mold, can pose all sorts of health issues, especially for those with sensitive respiratory systems. With roof leaks, or any kind of leak in general, there is a high chance that they will grow and rapidly reproduce because these leaks provide the most ideal breeding ground for them. Worse of all, their spores, which causes the most harm, will easily spread around via your HVAC systems.

These are just some of the most common, and probably most pressing issues that are associated with roof leaks. Make sure to get any leaks you discover in your home resolved soon, even better if you do it as soon as you find them. You don’t want to be surprised at how much you have to pay for all the necessary repairs if you decide to procrastinate on this task.

Best Algae-Resistant Roof Shingles

Because moss and algae on the roof have become a common household issue, manufacturers during the 1960s came up with roof shingles that supposedly prevent algae, and possibly even moss, from growing.

When they were first produced, these shingles were covered with an algaecide or algicide to prevent algae from settling there. Manufacturers decided to use zinc to not only prevent algae from growing but moss as well. However, its effects to the environment caused it to be discontinued.

At present, these algae-resistant roof shingles are made up of around 10% copper granules on average. This material is as equally effective as zinc, yet not that harmful to the environment. Do note that manufacturers differ on how much copper granules are included in the roof shingles they produce.

What you need to know is that these shingles supposedly only work for just a few years, not permanently. The copper granules get washed away completely over time, especially if rains are frequent. As a result, this layer of protection against algal growth is removed as well and you are left with a now-ordinary roof that used to be algae-resistant.

How Much Does Roof Cleaning Cost?

Due to the numerous safety risks involved, it hardly comes as a surprise that roof cleaning can get pricey. On average, you can expect to pay somewhere along the range of around $300 to $600. Roughly $400 is often the average rate of contractors for this type of work.

For simple roof cleaning jobs, contractors may charge you as low as $150. Unfortunately, removing algae and moss from your roof is not considered as a simple task. As a result, this kind of roof cleaning job is at the more expensive end of the spectrum, with rates reaching as much as $850. It gets even more costly if the algae, and especially moss, on the roof is already thick.

roof getting cleaned

Getting Quotes from Competing Contractors

If you decide to get a contractor to do the task, which is what we highly recommend you to do, you might wonder which one to hire. And if you are not even familiar with any of the contractors in your area, how would you even find them?

Fortunately, we have a service to do that for you and make it easier for you as well to get quotes from different contractors. All you have to do is fill out our form and the suitable contractors in your area will get in touch with you with their rates. It’s that simple!

But, it does not end there. Contractor rates in general are negotiable, so it is up to you to talk it out with them to get the best value possible. These professionals know that they have competition and the best way for them to get noticed by clients like you is to offer tempting rates and discounted additional services related to the job.

You may be tempted to go for the contractor that offers the cheapest rate, but what you should really focus on is the value they offer. Choose the contractor that not only quotes a reasonable price but also offers some extra services that you may find useful, such as free checkup of your roof gutters, adding waterproofing, or any other roofing task.

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