When Algae Attack

The algae subject is so extensive we have posted this article to help clear up myths and clarify facts regarding algae. Happy Reading!   

The black stains found on our roofs in Missouri is not mold, it’s actually a shingle eating bacteria called Gloeocapsa Magma (a.k.a. blue-green algae).[1]  Washing your roof with bleach only keeps it at bay for a 12 -18 months; conversely, washing it off every year will lead to early shingle replacement because the shingles cannot handle strong chemical baths on a repeated basis.  Left untreated the algae can cause roof replacement in as little as 15 years, not what you expected when you bought a 30 year rated shingle.

If you are reading this you probably already have black streaking in a few spots.  You’re most likely wondering why now, it’s been 7 years or more with no streaks and it’s everywhere.  Most shingles in our area include an algae resistant technology; to easily explain it, they simply add copper.  Once the copper wears away your protection is gone.  Over time the entire roof will turn black.  The trick is to catch it early, clean a few small areas, and then set up a maintenance plan to have the roof treated just as you would pest control for the rest of your home.


Unfortunately the algae is transported through the air, and it’s contagious, so if your neighbors have it you will too.  To quote an article sent to us by Owens Corning “Shingle manufacturers estimate that approximately 80 percent of all roof replacements are caused by this pest.  Gloeocapsa can end up costing homeowners thousands of dollars they may not need to spend”.[2]  Roof Doctor strongly suggests a community effort to battle the shingle eating bug.  After your roof is washed educate your neighbors about the dangers of algae, you are not only doing your neighbors a favor you are also helping yourself by cutting down on the risk of re-infestation.


If you want to find out whether or not your shingles are being damaged by the algae, simply compare the amount of granules in the gutters under the stained areas of your roof compared to the areas that have no stains, it will help you clear up any debates as to the ability for the algae to do damage.  You can also take a loot at your roof in the early morning hours or after a rain to notice the areas that have the algae are holding water longer; not only are they holding water longer, they are also soaking up more heat from the sun due to the dark color.  Algae causes granular loss which can lead to premature replacement of your shingles.  The algae naturally produces a dark pigment to protect itself from the sun, this is what eventually turns into the black streaks you see running down the roof.  The dark color causes higher utility bills because your roof is soaking in more heat.  Algae also releases organic compounds like nitrate and ammonia leading to lichens growth on the roof, a double whammy.[3]  Lichens are very bad for the roofing system because they can cause the shingles to lift and curl.  Once the shingles are raised they become a target for high winds.   Wind only needs to lift one row of shingles to allow many more rows to be stripped off during high winds.  If all of this were not bad enough, some insurance companies are even cancelling policies because of dirty roofs (follow this link to Channel 2 video: http://www.kjrh.com/money/consumer/dont-waste-your-money/insurance-companies-canceling-homeowners-insurance-policies-because-of-dirty-roofs).


At one time the dark roof problem was limited to the southern coastal states and other areas with high humidity, but the algae is becoming more resilient in less humid climates, combine that with the fact roofing shingles contain one of their most favorite foods and you now have an algae invasion in our neck of the woods.


There are many methods to combat the algae movement with each having merit.  The question is, which removal and prevention methods are correct for your particular situation?


Which cleaning chemical should you use?

Our research on the matter was based on the roof cleaning industries in Florida and Texas, areas where roof cleaning is an everyday event.  Most homeowners associations and property management groups are required to clean/treat roofs annually.  Instead of waiting for the problem to arise they simply treat the roofs with a preventative on an annual basis, in doing so they avoid costly cleaning services and never even see black streaking on their roofs.


Most shingle manufacturers will recommend following the ARMA (American Roofing Manufacturers Association) approved method of cleaning which includes the use of bleach and water only.  We find it unusual that ARMA recommends the one cleaning method that does the most harm to surrounding plant and aquatic life and is considered one of the most corrosive to metal flasing and gutter systems.


When it comes to Algae warranties most of them aren’t worth much after the 10 year mark, for example Owens Corning shingle warranty only covers labor and materials up to the end of year one, then the shingles are pro-rated for materials only up to the ten year mark as stated in the  current 2015 warranty version.  In most cases it would make more sense to try and clean a roof rather than replace it when you consider the labor is not covered after year one.


Some of you may want to always follow manufacturer’s recommendations and others may not.  Many people don’t want harmful chemicals anywhere near their roof or yards, where others feel they are getting a better job if they utilize strong chemicals and EPA registered preventatives.  Roof Doctor has developed a cleaning method that is 100% eco-friendly and will not harm aquatic or plant life.


Following is a list of cleaners and preventatives most commonly used in the roof cleaning industry.  There are many companies that provide a blend of surfactants mixed with the following chemicals.  Roof Doctor has researched and tested from the following list and has developed a proprietary wash system; therefore, in an effort to keep our methods a secret we will not be identifying which cleaners we use in this article.


Sodium Hypochlorite (a.k.a. Bleach) – Breaks down into Salt, Oxygen, and Water along with small amounts of AOX know to be toxic to shellfish and other marine and aquatic organisms.[4]


The ARMA recommends a bleach approach to cleaning shingles.[5]  Bleach is very effective when it comes to removing the stains, however in the strength it needs to be used the solution becomes very dangerous to use around your plants, grass, etc.  Bleach is not a weekend warrior project, it takes teamwork and diligence to pull it off.  If your home has plants, shrubs, grass, stained wood siding, stained decks, outdoor carpet or any other item that would discolor when hit with bleach, they would all need to be removed or covered during the cleaning process.  Anything the bleach hits can die or be discolored.  It is important to keep grass, shrubs, and plants wet during the entire process.  It is also important to keep wetting down the areas beneath the work area until finished, and do a final rinse on everything when done.


When roof cleaning companies say they are using bleach to clean your roof it is not the same stuff you buy at the local Walmart.  Professional roof cleaners use a concentrated bleach that usually has surfactants added to it to help the cleaning process.



1.  Shingle manufacturers recommend using it.

2.  It works well.  Bleach is great at removing stains, therefore it is one of the best chemicals to remove the black streaking caused by the algae.


1.  The ARMA recommended method requires no pressure to rinse, it is suggested that no more than a garden hose pressure be applied to the shingles.  The disadvantage to the garden hose approach is that it takes forever to fully rinse the bleach, and most likely you will not remove all of it.  It is similar to using a toothbrush to clean an entire bathroom.  High pressure wash or rinse methods are greatly denounced by the ARMA, so rising takes forever. It is very important to rinse well.  Bleach can dry out your shingles if too much is left behind.  It is incredibly difficult to remove the bleach with nothing more than a garden hose.

2.  At full strength bleach is dangerous to aquatic life.  Even if you mix it 50:50 it is still very strong.  In fact, if the bleach and water run-off enters any storm water drains, streams, lakes, or rivers, hereinafter, “waters of the United States”, it would be in violation of Section 301 of the Clean Water Act.  Our studies indicate that the ppm (parts per million) would be around 250,000 times higher than what is allowed in Table A, Chapter 7, of the clean water act.[6]  Notice we did not say “twice the legal limit” or “ten times the legal limit”, the amount is 250,000 times higher than the legal limit!  To put that into perspective, a swimming pool is only around 5 ppm, imagine jumping in a pool at 2,500 ppm.  F.Y.I.  You cannot even wash a car and allow the run-off to enter waters of the United States.  Washing vehicles is an example of a process water discharge of pollutants requiring an NPDES permit if it reaches waters of the United States.  EPA recommends that companies or individuals take their vehicles to car washes.  If a car wash is not available, NPDES permit requirements may be avoided and impacts on waters of the United States minimized if vehicles are washed in a vegetated or grassy area where the wash water will be absorbed into the ground instead of allowing it to run into the street and then into a storm drain.  There may be additional requirements if chemicals (detergents, waxes, etc.) are improperly used or if the absorbed water will reach an underground water body.[8]

3.  Bleach has a tendency to dry out anything it comes into contact with.  After the bleach breaks down it turns into salt and water.  High concentrations of salt left on shingles will lead to premature cracking and aging.

4.  If not properly protected, it will kill plants, shrubs, grass, etc.

5.  It is corrosive to the metal flashings on your roofing system.  Bleach is corrosive. "Bleach can drill a hole through stainless steel," says Curriden, "that's why it's important to wipe down metal surfaces with water or ethanol after treating them with bleach." For delicate metal instruments, consider avoiding bleach altogether and using a different kind of disinfectant, such as ethanol.[9]

6.  It will discolor anything it comes into contact with, including old paint, stain, patio furniture, decks, etc.  At the 50:50 ratio recommended by the ARMA you are around 80 times stronger than what you would use in a typical clothes washer.

7.  It receives an F score on the EWG (Environmental Working Group) website.[10] It is listed as very toxic to aquatic life, a subject of interest in the Lake of the Ozarks area.  The EWG is a great source to look up any household cleaner/chemical to find out if the product is safe to use.

8.  In most cases you will also have to pay for a gutter cleaning prior to the bleach washing method because it is crucial that the run-off goes down the gutter systems properly.  We don’t want any accidental overflows to run down painted or stained walls or onto deck systems causing unnecessary damage.

9.  It makes the roof very slippery.  Much caution is required to avoid injury.

10.  It is difficult to work with on a large scale.  The odds of getting it in your eyes, or breathing too many vapors are low if you are using it to wash clothes,  but in washing roofs you will be using around 15 gallons of product on an average roof giving way to many opportunities to injure your eyes or lungs.  When liquid chlorine is released, it quickly turns into a gas that stays close to the ground and spreads rapidly.  When chlorine gas comes into contact with moist tissues such as the eyes, throat, and lungs, an acid is produced that can damage these tissues.[11]  If you decide to tackle this yourself be sure to wear protective gear as recommended by the manufacturer.


Sodium Hydroxide (a.k.a. Lye) – Breaks down into Table Salt, Oxygen and Water

Sodium Hydroxide has been a long-time competitor with Bleach, it too has drawbacks and advantages.


1.  It is an excellent degreaser.  It is very commonly used for unclogging drains.  Works well in commercial settings that may have grease contaminants on their shingles.



1.  Concentrated sodium hydroxide is a very caustic chemical and can cause serious tissue burns in humans; if you splashed it in your eyes by accident, it could cause permanent blindness.

2.  When it's applied to plants, the sodium hydroxide could damage their tissues and more than likely kill them as well. The excess of hydroxide ions can participate in reactions like the breakup of lipids that cause serious harm to living tissue.[12]  Please note, the aforementioned citation is considering the Sodium Hydroxide at full strength, at the ratio used to clean it is not harmful to the surrounding plant life.

3.  It may also react to paint.  It has removed paint from gutters (the most likely thing that overspray hits) in some situations.  So, be careful or you may end up re-painting gutter systems.

4.  Sodium Hydroxide also received an “F” score at the EWG website.[13]

5.  Sodium Hydroxide is not very friendly with many of the components of the roofing system.  Sodium Hydroxide reacts with METALS (such as ALUMINUM, LEAD, TIN, AND ZINC) to form flammable and explosive Hydrogen gas.  Sodium Hydroxide can attack IRON, COPPER, PLASTICS, RUBBER and COATINGS.[14]

6.  Large amounts of caution should be used to protect yourself while using this product.  Always follow manufacture’s recommendations for protective gear.

7.  While bleach is considered corrosive, Sodium Hydroxide is considered very corrosive.

9. When dissolved in water or neutralized with acid it liberates substantial heat, which may be sufficient to ignite combustible materials.[15]


Sodium Metasilicate – Breaks down into Sodium and Metasilicate

Sodium Metasilicate is used in Degreasers, Oven Cleaners, Stain Removers, and other cleaning products.


1.  It does not damage the roof or surrounding vegetation.

2.  It is made from sand and soda ash, which is recognized as a non-pollutant.

3.  It is a bit easier to work with.  The manufacturer only suggests eye protection and gloves.


1.  It also receives an F at the EWG’s website mainly due to causing severe skin burns and eye damage.

2.  It too can react with paint on gutter systems or flashing in some instances causing the property owner to replace or re-paint metal surfaces.


Sodium Percarbonate (a.k.a. Oxygen Bleach) – Breaks down into Water, Oxygen, and Soda Ash a.k.a. Sodium Carbonate[16]

Oxygen Bleach is one of the newer chemicals introduced into the roof cleaning industry.  It can be very effective but may require more than one application to get the job done.  Once mixed with water it is basically hydrogen peroxide, similar to what you would find in your medicine cabinet.


1.  The only chemical to receive an A+ from the EWG

2.  It breaks down into water, oxygen, and sodium carbonate (a.k.a. soda ash).  Soda Ash is listed as benign to health and environment on the EWG’s website.  This is the most environmentally product we have found.  We can’t locate any evidence of it having harmful effects on plants, animals, or humans except for when the user is mixing it in powdered form.  Once diluted the chemical appears to have little or no effect that would be concerning.

3.  It won’t kill your plants, shrubs, or grass.

4.  It does not bleach anything.  It is color safe to stain, paint, patio furniture, carpet, etc.

5.  It does require gloves and eye protection.  But that’s it, no protective clothing or rubber boots unless you are working with the powdered substance then you do need a NOISH approved dust respirator.  We are told by our supplier that you could even stir the mix with your hand.

6.  When dissolved in water, it breaks down to oxygen, water and sodium carbonate that deodorize, bleach and clean while killing bacteria, viruses, fungi and algae.[17]

7.  It is viewed as environmentally friendly.

8.  It is the only chemical on our list that has more Pros than Cons.


1.  It is corrosive to aluminum, as all of the cleaners are, but in a diluted solution and with proper rinsing should not be an issue for the gutter systems.

2.  It does build up pressure once mixed, which can cause a container to burst.


Cleaner chemical review:

None of the cleaners mentioned will be capable of killing or removing 100% of the algae because the surface is so uneven.  It’s hard enough to remove things from clean non-porous surface, imagine trying to remove them from a surface similar to the moon.  Having said that, it is crucial to get on a maintenance plan that includes annual treatments.  In most areas of central Missouri, more specifically, Jefferson City, Osage Beach, and Springfield Missouri areas you are likely to go every 3 years between preventative applications on your maintenance plan.  If everyone in our area would simply start a maintenance plan at the very first sighting of a small black area it would be possible to permanently avoid the expensive cleaning process.  Unfortunately most people wait until they have a bad problem and then react.  Being reactive instead of proactive sets you up for an expensive fix because you have to first clean the algae and then pay for an algae preventative application.  Catching the problem early is key, or even better, treat your roof with a preventative before the streaking occurs.


We can’t finish our review on chemicals without giving the bad guys (Bleach and Lye) a chance to redeem themselves.  It is important to understand that the warning labels and bad reviews all speak about the product in their raw form, straight out of the container.  If used properly, in diluted form, all of the aforementioned can be used without harming the user or the environment. The biggest concern is spilling the un-diluted product, or having run-off into yards, lakes, streams, or storm drains.


Which chemical is best for maintenance?


Before we discuss which preventative to use we need to take a look at the politics of product labeling.  I am sure many of you have heard the term EPA registered.  What does that mean?  Is it safe because it’s registered, or is it bad that it’s registered?  The short answer is both, the reason the chemical gets registered is because it is making a “kill” claim, that means it is dangerous and needs to be used according to the label and only by those approved to apply it; on the other hand, it is a good thing because proper labeling can lead to proper use, thereby making the product safe to handle and apply.


To speak on the politics of the matter we feel it is important for you to understand that both products we are using may, or may not kill, the precise bacteria (gloeocapsa magma a.k.a. blue-green algae) because neither product is laying claim on their labels that the product will perform the “kill” function on our specific bacteria.  What separates the two is that one manufacturer decided to spend millions of dollars to get his product EPA registered to make the “kill” claim for many types of bacteria and viruses, while the other decided to spend their money on marketing instead.  This has been the most frustrating part of our research completed prior to offering the cleaning service to our clients.  The irritating problem with all of the preventative products we have found it that none of them have been specifically tested to “kill” our little algae friend.  Conversely, none of the cleaners have been specifically tested to “kill” our little algae friend.  The question is why?  A couple of theories would be the fact that it takes up to a decade and millions of dollars to be able to make the EPA registered claim; while another theory could be that the roof cleaning industry does not produce enough customers willing to break their necks climbing around on a roof to buy the product from the box store shelves, making the expense of getting the “kill” claim unworthy of the cause.  Nonetheless, here we are, using products that are widely recognized to do the job, but have no official backing other than customer satisfaction reviews.


Most of our research was completed in Florida where the algae is very fast to repopulate a roof.  The best of the best roof cleaners in many coastal regions can only keep the algae at bay for one year, but at least they have figured out that treating the roofs annually does work, even though they do not have any products that specifically list our little problem child.  Our apologies for the long explanation, but we want you to understand that we have confidence in both of our preventatives even though one of them is not EPA registered.  The reason we offer both is to give our clients a biodegradable, non-corrosive option.

EPA registered algae preventative


1.  The product has been tested and does make a claim to kill a broad spectrum of bacteria.

2.  Not harmful to the plants.

3.  Not harmful to water.

4.  Not harmful to ozone.

5.  Non-acid.


At the dilutions we are applying the product we have not been able to determine any risks.

Non-registered algae preventative


1.  Listed as bio-degradable and non-corrosive.

2.  Not harmful to the plants.

3.  Not harmful to water.

4.  Not harmful to ozone.

5.  Non-acid.


1.  It is not an EPA registered product.


Are there other preventative measures?

There are two other methods of prevention.  The first is to apply zinc or copper strips at certain points along the roofing system.  The second is to use a sealant that slowly releases a preventative chemical over time.


Copper and Zinc Strips

As a roofing company that is most concerned with giving our clients a good product we cannot in good faith recommend using metal strips because they are invasive to the roofing system.  Roofs are not intended to have “add-ons”.  It is way too common that you see the cable tv guys putting dishes on roofs and then just sealing the holes with caulk.  The caulk will absolutely fail over time, no roofing system is made to be jeopardized once installed.  To install the metal strips you are forced to break thermal seals and then put a new sealant in their place in an attempt to seal metal to the back side of a shingle.  This is a perfect example of jeopardizing a roofing system.  Once you get past the bad mechanics of installing an “add-on” you might want to consider if you want to look at ugly metal strips along your roofing system.  Our research indicates that the metal strips only work to protect the area 4-10 feet beneath where they are installed because they rely on rain waters to rinse minute portions of the metal across the roof surface.  The presence of the metals deter algae growth, of which you can see an example of this by looking at your own roof.  In the areas that you have metal flashings you will notice the areas directly beneath them do not have any algae stains.  However, if you have a large enough roof you will notice the area will only be 4-10 feet long that it is effective and then the algae will show again.  If you could apply a small, not very visible, piece of metal along the top ridge without risking the integrity of your thermal seals it could be a viable option.  However, it is doomed to fail before you get started.



There are several companies producing sealants in the industry that not only provide long-term algae protection but they also improve the roofing system’s ability to fight high winds, which could be of great benefit to many of the multi-family structures that pay roofing companies like ourselves to replace wind-blown shingles every time a strong storm passes by.  Most people do not understand that the damage done to homes in tornadoes and hurricanes is due to the shingles blowing off, allowing the decking to be exposed, and then the roof goes.  One of our suppliers has undeniable proof that their sealant saved homes in both Florida and Louisiana during hurricane force winds.  It was quite amazing to see the photos of homes with roof after roof damaged and in the middle of it all stands a perfect un-damaged property because they made the decision to apply the sealant.  We will give this product two more acts of brilliance.  The first would be to include a biocide in an acrylic product, it's a great way to slowly release the product over time thus decreasing ugly black stains for prolonged periods.  We believe that one treatment could last as long as five years in the KC & St. Louis Metro, Columbia, Jefferson City, Lake of the Ozarks & Springfield-Branson, MO areas, but since this is a relatively new technology only time will tell.  The second would be that each time the sealant wears down you could apply another coat, just like painting a home.  Have you ever seen a 100 year old home that has the original siding?  I am sure you have, but did you ever stop to think about how many times new shingles have been put on the roof?  Why would we continue to replace shingles if we could just “re-paint” them with a clear acrylic every 7-10 years?

Trust us when we say the sealant approach reaches new levels of brilliance.


To review, there are several cleaning and prevention methods in the roofing industry.  We feel it is crucial that you hire a qualified roofer to complete the cleaning process as the cleaning business is un-regulated.  As qualified roofers we will be able to recognize manufacturer’s defects, make small repairs, and not damage the shingles in the process.  We come pre-trained in safety and know the limitations of a shingled roof. 3 Step Roofing is not just a name, we can prescribe the right chemicals to clean and prevent algae problems specific to your needs.


3 Step Roofing,

Saving roofs daily…..



1.  http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=685

2.  Article: Copper Ions Keep Roofs Clean (received from Owens Corning)

3.   https://microbewiki.kenyon.edu/index.php/Gloeocapsa_magma

4.   https://www.clorox.com/dr-laundry/bleach-101/

5.   http://www.asphaltroofing.org/

6.   http://www.sos.mo.gov/adrules/csr/current/10csr/10c20-7a.pdf

7.    http://www.sos.mo.gov/adrules/csr/current/10csr/10c20-6.pdf

8.   http://www.epa.gov/region6/6en/w/pw.htm

9.   http://www.scripps.edu/newsandviews/e_20060213/bleach.html

10.   http://www.ewg.org/

11. http://www.bt.cdc.gov/agent/chlorine/basics/facts.asp

12. http://www.ehow.com/info_8345895_sodium-hydroxide-kill-plants.html

13. http://www.ewg.org/guides/substances/5570

14. http://nj.gov/health/eoh/rtkweb/documents/fs/1706.pdf

15. http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=248&tid=45

16. https://www.mineralseducationcoalition.org/minerals/sodium-carbonate-soda-ash-or-trona

17. http://www.ehow.com/how_10023116_clean-decks-sodium-percarbonate.html