Tuesday, April 16, 2024
HomeFactsWhat Causes Black Streaks On Roof Shingles

What Causes Black Streaks On Roof Shingles

What Are Those Ugly Black Streaks On My Roof

Clean Black Streaks from Roof Shingles

Although these dark spots and ugly black streaks on your roof may look like dirt, mildew, soot or mold, what they really are is algae. The most common type is known as gloeocapsa magmaâalso known as blue green algae.

This algae growth usually begins as small spots and then eventually becomes visible streaks. By the time this algae is noticed by the homeowner, it has usually been on the roof at least two or more months.

Why does this algae appear to be black? Gloeocapsa has the ability to form a protective darkly pigmented outer coating that shields the algae from damaging UV rays. This is what makes those unattractive black streaks on your roof!

Although algae can be found on all types of roofing, it tends to be most common on asphalt shingles.

Why Are Algae Colored Black

Its not the algae that are colored black. Rather, its the protective pigmented outer coating they produce to protect themselves from the suns harmful UV rays. As algae continue to proliferate, so does this black substance, causing black streaks to appear all over your roof.

Algae are not harmful to your health, but they are so unsightly that its always better to be rid of them. If left to thrive, these algae can also attract fungus, resulting in lichen growth. Once lichen has taken root, getting rid of algae becomes more difficult. This is why its recommended to clean the roof immediately at the earliest sign of moss. Remember, the longer the algae stay on your roof, the harder it will be to remove them.

Besides, black streaks dont exactly look good on your roof. If you want to maintain your propertys curb appeal, you need to get rid of all that algae.

What Causes Roof Stains

If youre a homeowner, youve probably noticed those long black stains on your roof or a neighborhoods. This discoloration makes your roof shingles look wet in certain places. Untreated, these streaks can become long and unsightly, detracting from your curb appeal. But you dont have to leave these roof stains to grow and spread there is a way to clean your roof and prevent these stains in the future. Read below to learn all about black roof stains and the black algae that causes them.

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How Do I Get Stains Off My Roof

If the algae keeps reappearing on your roof despite regular washing, consider replacing your shingles with mold and algae-resistant roof shingles. Another option is to install zinc metal strips near the ridge caps at the top of your roof. Zinc is a natural algae inhibitor, so any rainfall that hits the metal strip will carry the zinc down and over your shingles.

Heres a how to remove algae from your shingles:

*Make sure to do your cleaning on a cool or overcast day with minimal wind, and wear protection

*Prevent damage from overspray by removing any lawn furniture, and cover landscaping and vegetation

*Use an appropriate cleaning solution or a homemade mix

*Pour your cleaning chemical into a pump-type garden sprayer and thoroughly spray the roof

*Let the solution sit for 15-20 minutes, and then give the roof a good rinsing

*Use a garden hose to re-rinse the roof as many time as needed to remove any residue from the cleaning solution

Forensic Sampling Of Roof Stain Material

Black Streaks on Roofs: What Are They and How To Get Rid ...

A simple collection of the stained roof surface material using clear adhesive tape followed by a laboratory analysis by an experienced microscopist is conclusive. We don’t recommend lab sampling of shingle stains in most cases but if you want to sample a stain material for analysis in our forensic laboratory, instructions are

Don’t bother worrying about mildew on your roof. Mildew is an obligate parasite which grows only on living plants. Unless your roof is covered with grapes it is not likely to have much mildew there.

Also see TEST LABS – ROOF SHINGLE for chemical and durability tests on roofing materials.

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What Causes Algae Growth

Algae grows from spores. These spores travel through the air, probably from a distant neighbors roof, and eventually land on your shingles. The algae uses the limestone found in asphalt shingles as a food source and eventually starts to grow. Areas with high tree density or high humidity can speed up the growth process. By the time you see the streaks running down your roof, the algae has probably been growing for a few months.

The Dangers Of Algae On Your Roof

Because the algae is feeding off of the shingles, it will eventually damage them. As the integrity of your roof shingles deteriorates, the protective layer that covers them starts to wear down. This dries out your shingles and can cause them to fall off your home. Algae also traps moisture on your roof which can promote the growth of lichen and moss. Because lichen and moss have roots, it can cause even more damage to the roof than the algae originally did.

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How To Distinguish Roof Stain By Type Of Proximate Cause Color Source

There are many sources of roof staining and they vary in significance, from cosmetic to harmful to the roof. Here we give an index of all sorts of roof stains and what causes them.

Dark black or brown roof shingle stains are often caused by black algae, bleed-through or extractive bleeding of asphalt, dirt, soot, or organic debris. But there are other roof stain colors and causes. The remedies for and means of preventing stains on roof shingles are discussed as well.

For example, if you see stains around or below a chimney, take a closer look at the chimney as the stain source. It’s pretty easy, right?

The red stains on the roof shown at left are almost certainly from rusting metal, perhaps rusty chimney flashing. These stains, cause ,and cure are discussed and diagnosed


In the photo shown at page top, the black stains on the lower roofs are bleed-through or extractive bleeding. The upper roof, shaded by the large tree in the page top photo, was also moss covered.

Notice the streak of “clean” roof shingles that lack the stains on the upper roof near its left edge? Those shingles were installed down-roof from an aluminum attic vent fan cover. The aluminum salts washing off of the fan cover prevented moss, lichens, and algae from growing on those shingles.

As stated in Best Practices Guide to Residential Construction:

What Causes Black Streaks On Shingles

Algae Resistant Roof Shingles By Atlas Roofing Featuring Scotchgard Protector

The dark stains or streaks that sometimes form on shingle roofs are usually a sign of a Gloeocapsa Magma infestation. This is a species of bacteria that resembles algae and thrives in damp and cold environments. Its very likely to show up in humid climates, or on surfaces that receive plenty of dew or shade.

Since the north-facing side of a roof is normally the side that gets the least amount of sunlight, this is where the first streaks will usually appear. However, they can also occur in areas that have significant tree coverage. Since Gloeocapsa Magma spreads via air, theres a significant possibility that it will soon infest the surrounding roofs as well.

On top of being an eyesore and reducing the curb appeal of your home , this bacteria also absorbs and holds moisture. If left untreated, it can cause your shingles to age, rot, or lose their granules prematurely.

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Preventing Black Streaks On Your Roof

Can you permanently get rid of algae? The short answer is âno.â Roof algae is similar to having a cold. Like many cold viruses, algae spores are airborne and unavoidable. You can treat the symptoms, but eventually you will have another algae problem, especially if those around you have it on their roofs as well.

But donât despair! Like washing your hands frequently and eating healthy to prevent catching a cold, cleaning and maintaining your roof can help prevent black streaks on your roof from returning. Here are some ways to keep roof algae at bay:

Maintain Your Roof

Trim tree branches to allow more sunlight to reach the roof and minimize the accumulation of debris. Debris that does begin to accumulate on the roof should be cleared regularly by hand as part of a regular maintenance program. This will provide an environment less inviting the growth of roof algae.

You should also keep gutters and downspouts clean and free of clogs to promote proper water drainage. Never allow gutters or downspouts from an upper roof to drain directly on a lower roof extend the downspout from the upper roof into the lower gutter.

Gutters draining onto a lower roof not only promote algae growth but can cause water to pool on your roof, which can damage shingles as well as the underlying wood structure.

Install a Copper or Zinc Strip Along the Side of the Roof

Get New Shingles

What Are Those Ugly Dark Streaks On Your Roof And What Can You Do About Them

Theres nothing more frustrating than spending a lot of time and money on a top-quality roof that looks great and provides unparalleled protection against the elements, only to come home one day and notice that your new shingles are covered in ugly black stains.

But what are these streaks, and why do they appear? Are they just an eyesore, or can they actually damage your roof? Can you remove these stains yourself, or do you have to schedule professional San Diego roof maintenance services?

In previous articles, we stressed the importance of regular roof maintenance and explained why roof cleaning is a must. Now well explain why dark stains sometimes appear on your roof shingles and how to get rid of them. Read on to learn more.

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Prevent Black Streaks From Growing On Your Roof

You already know why black streaks are appearing on your roof. It makes you wonder: What could I have done to prevent them from growing and spreading? After all, prevention is better than cure, right?

But before we dig deeper into the answer, lets get one thing straight: you cant get rid of algae completely. Algae are like the common cold. They are always out there. But just like with the common cold, you can take precautions to prevent your roof from catching them. Its equivalent to washing your hands regularly or putting on a face mask in public places.

Black Streaks On Roof Shingles Heres What To Do

Black Streaks on a Roof (Causes &  How to Fix)

Have you noticed black streaks on roof materials or patches along your rooftop, especially in the shade? Roof shingles often fade into lighter colors over time, but sometimes the opposite effect can occur thanks to subtle plant growth. Fortunately, there are ways of removing those black patches.

Black streaks: Blame the algae

Those black streaks on your shingles may look like problems with old age or damage, but they are really caused by algae specifically, gloeocaspa magma is usually to blame for those wavy, dark shades that grow as the algae bloom spreads.

Many homeowners are surprised to find that algae is growing on their rooftop, because algae is usually associated with pools and seashores. However, given the right conditions it can also flourish on shingles: Those conditions include plenty of moisture or humidity , and the right kind of minerals for the algae to feed on.

So, how do you know if those black streaks on roof shingles are indeed algae, or a different problem? One of the best signs is how the algae behaves around metal. If you have metal vents, chimneys, or metal flashing along your roof, take a look: Do the black streaks die out around and underneath those metal pieces? During rainfall, elemental traces of zinc and copper often leak down from metal through your shingles. These traces are poisonous to algae, which will avoid these sections of your roof.

Getting rid of the algae

Algae-resistant materials

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How To Remove And Prevent Black Algae Stains On Asphalt Shingle Roofs

If you live in a humid area of the country, youve probably seen unsightly dark streaks on asphalt shingle roofs. Though often attributed to an accumulation of dirt, defective shingles, mold, or mildew the most common culprit is actually a blue-green algae known as Gloeocapsa Magma that is spread by airborne spores.

While algae growth does little harm to roofing, the stains dont help the overall appearance or resale value of your home.

You may also have noticed that algae stains are absent directly below the metal flashing around chimneys or roof vents. This is due to fact that copper and the zinc coating on galvanized sheet metal are toxic to algae. Every time it rains, trace amounts of metals are washed down the roof, inhibiting algae growth.

Where Can I Hire An Acclaimed Roofing Service In Mount Laurel Nj And Throughout The Mid

If youre in need of an established home improvement company that can provide you with a broad selection of roofing, solar, window, door, siding, and gutter services, look no further than Nu Look Home Design.

We are an Owens CorningTM Platinum Preferred Contractor that boasts a satisfaction rate among customers of no less than 94%. We will happily attend to the needs of your home while you deal with your other responsibilities or relax at the Mount Laurel Community Center.

Our services are by no means limited to Mount Laurel, so dont hesitate to contact us if youre located elsewhere in New Jersey, Maryland, or Virginia.

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Where Does It Come From

The algae travels with the wind, which is why its so easy to find from house to house. If one house in the neighborhood has it, all houses are at risk. Although blue-green algae can get its water from rain, it doesnt need it dew and humidity are all it needs to thrive.

Black streaks are far more prevalent today than ever due to the ever-increasing limestone content in shingle manufacturing. Mold is attracted to limestone, so manufacturers will coat some of the granules on the singles with copper in an effort to mitigate any mold or algae growth.

Some manufacturers make algae-resistant shingles that include a larger copper content, which will come with a longer warranty, as well. You should take note of exactly what your warranty covers, thoughthere are many different types of mold, algae, lichens, and moss, but only certain types are covered.

Heres What People Love About Home Pro America For Their Roofing Needs:

Roof Problems – Ugly Black Streaks On Asphalt Roof
  • TrustworthyOur reputation and results speak for themselves. Take a look at what others are saying, and see our gallery.
  • Licensed and insured roofing contractorWe care about protecting you and our team. We carry extensive insurance that gives homeowners peace of mind.
  • Solid communication with homeownersEnjoy open, straightforward communication from our team.
  • Experienced at insurance issuesGet a thorough report to streamline the insurance process.
  • Skilled roofers offer exemplary roofing replacementWe do installations right the first time from start to finish.
  • Stress-free roof replacementGet the roof you need, and enjoy the process. Relish a secure, well-protected home.

Your home should look beautiful. Get the curb appeal youll love coming home to again. If youre having trouble with black algae issues, Home Pro America can help. Well get the eye-catching curb appeal you love restored with a new roof you can enjoy for years to come. Schedule a free consultation.


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Erase Black Streaks With Wet & Forget

Wet & Forget Outdoor breaks you out of the cleaning cycle. Wet & Forget Outdoor eliminates black algae on your roof with no scrubbing, rinsing or pressure washing needed.

Just spray and leave! Wet & Forget Outdoor works with the wind and rain over time to completely wipe out black algae and keep it away for a year or more in most cases.

Wet & Forgets gentle, non-caustic formula is safe for all types of shingles, and it wont corrode your downspouts or harm your lawn with runoff.

Because it works with the rain, Wet & Forget Hose Ends cleaning power reaches the nooks and crannies of textured surfaces such as asphalt shingles much better than your scrub brush can for a more thorough clean, without the extra wear and tear that all that scrubbing puts on your shingles.

Causes Of Black Streaks

While there are several possible culprits behind the black streaks on your roof, the most common cause by far is gloeocapsa magma. This hardy, blue-green algae is commonly found on asphalt shingles because it feeds on the limestone that is commonly found in these types of shingles. This algae thrives in moist areas, so theyre especially prevalent in areas known to have very humid climates. Shaded, moist areas on your roof highly encourage algae growth. They trap in moisture and feed on your shingles.

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Its Worth Every Penny

In the long run, paying a professional roof cleaner for regular cleaning is worth the money. First off, roofs that are cleaned on a regular basis tend to have a longer lifespan. While paying a roof cleaner costs money, its much cheaper than going for a full roof replacement.

Roof shingles arent exactly cheap, and considering the amount of work that goes into replacing a roof, paying a high amount for manual labor is also to be expected. If you want to spend less on your roof, you need to think of it as an investment. And the only way for you to maximize that investment is to spend money on it.


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