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Post Info TOPIC: 10 Steps to Algae, Moss and Lichen Growth and what to do about it.


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10 Steps to Algae, Moss and Lichen Growth and what to do about it.

When looking up at their roof, while scratching their head or rubbing thier chin in contemplation, some Homeowners may ask:

"What are those darned roof stains?"

“Just what is that black streaking and those discolorations, making my roof look so unsightly and unappealing?”

Maybe you, as a residential or commercial property owner, are asking yourself the following questions:

“Why should I clean those stains off my roof?  Hmm, I wonder, are they doing any real damage or is it just that they are not so attractive from a curb appeal standpoint?”

The answer is yes on both accounts … the ugly roof growth will damage your roof and is not very nice to look at compared to the look of a fresh, clean, rooftop.
First, the black streaks on your roof aren’t just an eyesore, they are supplying the organic material that for Lichen and moss to root into your shingles.  Once this food source is present, moss and lichen will soon start to grow and multiply.

Below I have outlined the process and stages of roof deterioration, what to look for and also what may already be ALREADY happening up on your roof.

It is so unfortunate that many yet to be Roof Clean USA customers are unaware of just how Algae, Lichen, Moss, Mold, Mildew and atmospheric contaminants on their roof is being hidden by the gradual initial algae discoloration. 

Unfortunately, on advanced or severe cases of algae and moss and lichen infestation there will be granule loss on the shingles from the massive amount of mature Gloeocapsa Magma root system now deeply embedded in them.

No homeowner should ever let their roof get to these advanced stages of roof infestation and untreated, unmaintained roof plant growth.

The process of roof debris accumulation is a gradual one but a damaging one, nonetheless.

1. First, the roofing shingle manufacturer placed crushed limestone in the shingles used a filler, binder to the fiberglass and asphalt shingle matting which made the modern shingle, a natural snack food "pit stop" for the blue -green cyanobacteria GLOEOCAPSA MAGMA algae.

2. Then, Two, the algae was allowed by the homeowner to start growing and then remain on the roof until it was in "full bloom" and covering most of the Northern facing, roofs exposed areas, then later, as the roof continued not to be maintained and properly cleaned, the algae continued its growth as their was never any treatment or biocide or fungicide agent applied (ever) to stop its rapid growth, and soon it covered the entire roof surface.

3. Once the bed was made, i.e. the algae had propagated, sheathed itself by developing its dark colored husk and turning black to protect itself from the sun's rays, it continued to grow and grow, until it built a thick bed of algae, holding in the accumulation of the overnight moisture, roof condensation and dew, which allowed the next phase to occur.

4. This next phase is when their is all the right ingredients for additional growth of OTHER organisms BESIDES the GM algae, such as , LICHEN, MOSS, etc.

5. Once the bed has been made by the HOMEOWNER, neglecting to safely use non pressure roof cleaning methods, like the methods and teaching, here on the ARCA and RCIA, the algae was given all the opportunity it needed to "INVITE" additional "roof dwelling friends" to the party up on the homeowners rooftop.

6. This final stage is when the most damage can occur, when the algae has a thick bedding made and moisture is allowed to soak up into this algae bedding like a sponge, holding many other nutrients that occur by the gradual decomposition of the combination of the dying, re-propagating and shedding of the protective outside layers of the GM algae or husks, in combination with the crushed limestone roof shingle filler "combined" so that the roof now has all the ingredients to grow this moss and lichen.

7. This moss and lichen and algae are like any other plant. They have a root system. Once the roots are firmly planted and embedded in a homeowner’s roof, the roots actually suck or pull nutrients out of the shingle, AND, the roots also tug and pull on the roof shingle GRANULES, thereby dislodging and removing them from the shingle.

8. Granule loss exposes the shingle roof to the repeated day in and day out of the SUN'S brutal and harsh ray's and without the important Ultraviolet Protection, that the granules are designed to provide, the essential oils in the roofing shingle are leeched out of the shingle, causing the shingle to prematurely dry out and become brittle and soon curl and break.

9. Once the roofing shingle has all of these elements occurring, the damage is now partially irreversible and eventually the roof will leak if not replaced, from this massive microscopic attack on the roof at this advanced stage of lack of roof maintenance. Fortunately homeowners can do something proactive about this in the early stages of this problem and the results will be maximized roof life and that is depended upon how seriously each property owner takes this growing algae infestation so as to keep all we hold dear and important to us, safe, dry and free from water damage and harm..

10. Luckily, much of this can be avoided by proper, regular annual roof maintenance. Simply put, if annually, a homeowner can be very influential if they will just do his /her part to extend and maximize their roofs longevity by contracting with a ARCA or RCIA certified roof cleaner and getting a simply, low cost treatment applied to provide a barrier to block the algae, etc. from getting a foothold on your roof surface, their roofs life can be substantially increased and they may also save themselves thousands in expensive tear-off and re-roofing.

In closing, every homeowner should annually get their roof checked for the presence of roof algae, moss, lichen and mold. If any of these are present, the roof should be scheduled for a non pressure roof cleaning by a ARCA or RCIA Certified Roof Cleaning Professional Contractor. Then, once the offending algae, lichen or moss growth is controlled, the homeowner should get set up for annual anti- algae roof treatments to keep their roof looking and performing its very best.

Written by- David Westerman. David is a Non Pressure Roof Cleaning Expert and National Safe Practices trainer, with 20+ years experience in the pressure washing and non pressure roof cleaning trades. David is Founder of A-R-C-A, the American Roof Cleaners Association. .David is also the owner of Roof Clean USA, a safe, non pressure roof cleaning company based in Thomasville, Georgia 31757. David can be reached at 229.227.0000 

Copyright 2008-2010 Roof Clean USA - All Rights Reserved-No copying or unauthorized reprinting allowed unless specific permission is granted by the author.

Roof-Cleaning-GA Blog
Roof-Cleaning-Georgia Blog


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Good Lord is that good stuff. You are a true professional. Very nicely done.


Brad R. Iannacchione
Soapy Roof, LLC
New Kensington, PA 15068

Premium Member Roof Cleaning Institute Of America Certified Roof Cleaning Specialist

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Posts: 657

Thanks David, As always great info for us


Kleen Roofs & Exteriors

1111 Nixon ave. nw

Grand Rapids, Mi 


Kleen Roofs


Pictures of our work


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Posts: 237

OOooooooooooOOOOOOooooooo...algae,moss and lichen are SO scary! I once saw lichen grow legs all the way to the ground and start to walk away with the customer's roof before he was willing to admit he had a problem. My twelve year old son is going as the Lichen/Moss Monster for halloween this year.furious.gif



Ada Mobile Wash

2694 Ashville Dr. NE

Grand Rapids, MI 49525


Roof Washing Exterior House Cleaning Grand Rapids, MI


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Thanks for the info...


Jeromy Ashcraft

Satcahr - Handyman Services

Done once, Done right!

RCIA Founder

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This would be good material for a roof cleaning blog guys ?
Notice the add this button ?
It is easy to add posts from RCIA to different places.
Be SURE and credit Dave ??


Apple Roof Cleaning Tampa Florida

711 Westbrook

Brandon, FL 33511

813 655 8777

See our website here 

Click here for more information

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Dave, that is very valuable roof cleaning information right there. Thanks for sharing.

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