Mold Infestation and What It Does To Your Roof

The Mold Infestation and What It Does To Your Roof

How To Extend The Life Of Your Roof

There is no doubt that mold and mildew is ugly and ruins the appearance of your roof. Mold sometimes creates a damp musty feeling and smell around a home as well. With that being said what else does mold and mildew do to your home and how does it effect you? Is it different or worse here in Florida?

Gloeocapsa Magma. Ever hear of it before? Perhaps you haven’t heard of it but we guarantee that you have seen it. Curious?

As a licensed roofer in Orlando we have dealt with many different types of roofs infested with this bacteria so stick with us and in this article we will explore what mold and mildew does to your roof and what you can do about it.

Gloeocapsa Magma is a species of bacteria in the gloeocapsa genus of cyanobacteria, from a family of photosynthesizing bacteria, which photolyze water generating oxygen gas. Cyanobacteria are related to the chloroplasts of all plants on earth. Gloeocapsa Magma may resemble “algaebecause they are both green, but in fact cyanobacteria are actually bacteria, whereas algae are single-celled eukaryotes (cells with nuclei) that are closely related to plants.

Algae and Gloeocapsa Magma are the first wave in a succession of organisms that can colonize and ultimately undermine a roof. The algae can eventually team up with a fungus to form lichen. Moss follows, building a small layer of soil that might catch seeds from bird droppings. By the time grass sprouts between the shingles, it’s past time for a new roof. The process can take years.


Infestation Especially Heavy In The Southeastern United States

Gloeocapsa Magma became more well known in the Southeastern United States, particularly in Florida during the 1990s, but it has since spread throughout the rest of the United States and Canada. 

Here’s the issue though. Whereas it used to be that dark streaks were primarily a problem on roofs in damp climates, we now see it occurring on roofs in virtually all climates. And, it’s not really a marker of roofs that have some age on them. We see Gloeocapsa Magma occurring on roofs that have been up as few as three years, making a roof look much older than it really is!

So, what has changed?

In order to keep down the cost of composition shingles, manufacturers have begun to include more “fillers” in their “recipes”. These fillers replace some of the oils in the shingles. Of course, those oils are normally the most costly component of the shingles. Removing the oils often seems to shorten the lives of the shingles, making them less resilient and supple. But, an additional problem is that the Gloeocapsa Magma feeds off of those fillers, leading to the unsightly streaks and stains.

A predominate filler used in composition shingles, because it is so plentiful and inexpensive, is limestone. It is the calcium carbonate in limestone that Gloeocapsa Magma really likes to feed off of, along with moisture that naturally collects on a roof’s surface.

This particular type of cyanobacteria is responsible for creating black stains and streaks on roofs. The bacteria accumulate over time because of the fact that it feeds on moisture and calcium carbonate. This accumulation begins to show the black stains as the cyanobacteria develop their dark and hard UV-protective outer coating.


The main reasons for the rapid spread of these cyanobacteria are thought to be:

Rising humidity and temperatures combined with more bacteria spores because of them being carried by the wind promotes their spread with these favorable conditions.

Fiberglass shingles are made with limestone as a filler in the asphalt. These shingles hold moisture and organic “bacteria food” material longer, especially on the North-side of roofs than the paper/asphalt/ceramic shingles of the 1980s.

A combination of humidity, moisture and possible tree coverage that promotes more moisture and algae growth. Also because they are carried on the wind from one place to another, like your neighbors home. This causes them to spread even faster from neighboring houses.

This cyanobacteria causes substantial destruction to roofs causing shingle decay and loss of reflective power. Over time, Gloeocapsa magma breaks down the shingles by feeding off of the limestone granules embedded in the shingles. This decreases a roof’s ability to reflect ultra-violet rays of light and shortens the life of the roof.


Once the bacteria have become noticeable, the infestation will continue to worsen year after year. As the bacterial colony grows, gravity causes them to spread all over the roof working their way downward, resulting in the dark colored patches that resemble stains down your roof. Most experts consider the bacteria to be harmful, if left untreated, as the growth holds moisture within shingles causing premature aging, rotting, and/or granule loss.


Gloeocapsa Magma is also harmful to wood shake roofs as well. It discolors the roof and causes the wood shake shingles to rot and decay prematurely.


The buildup of Gloeocaspa magma on residential properties has led to premature roof replacements, lowered property resale values, insurance companies canceling policies and increased utility costs as the black stained roofing draws in more heat.


Lowers The Resale Value Of Your Home


The amount of gloeocapsa magma on a rooftop is a common way in which people estimate the age and condition of a home’s roof. If a home has a lot of dark streaks on the roof, prospective buyers of that home assume the roof is on its last legs and, as a result, the roof condition becomes a bargaining point for the home’s value. Beyond that, these dark stains also have a huge bearing on the curb appeal of a home. If you’re like most homeowners, that means something to you. You want your home to look as nice as possible and Gloeocapsa Magma just detracts from its overall beauty.


Energy Costs


You may not think of your utility costs when you see this infestation on your roof, however, it does present a problem. Approximate savings after having your roof cleaned is estimated by some experts to be up to 30%. So that is reason enough to have your roof cleaned so the infestation can be eradicated.



There are many available options for the eradication of Gloeocapsa Magma, the most common and most widely accepted solution being an application of Sodium Hypochlorite as well as Copper Sulfate. Most licensed roofers in Orlando prefer the former Sodium Hypochlorite.

The preferred technique for the application of these chemicals is low pressure washing. This will avoid costly damage to the roofing and structure. Most licensed roofers in Orlando and roof cleaning contractors prefer this method of cleaning.

Also, Sodium Hypochlorite solution is what the Asphalt Roofing Manufacturers Association recommends

Roofing experts warn against using pressure washers on asphalt shingles because that can damage the shingles and do a poor job of removing algae.

My wife and I recently noticed Gloeocapsa Magma or algae on our 13 year-old roof, as well as lichens, which look like greenish-white splotches made with a paintbrush. Fortunately, we didn’t have any other growth, such as moss, which can grow in between the shingles and cause damage as well.

     We used the solution of Sodium Hypochlorite and it made our roof look like new again. Imagine how you will feel with a freshly cleaned roof, that not only will improve the aesthetic appeal of your home, but extend the life of your roof, and save you money on your utility costs. 

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