What is on your surfaces?


Algae are simple plants, microscopic (microalgae). Microalgae include both cyanobacteria, (similar to bacteria, and formerly called “blue-green algae”) as well as green, brown and red algae. In our photo at above left shows a common condition that is found on many types of building siding: green (or brown or black) algae growth.
Algae is a naturally occurring (pesky) moss-like plant that spreads by air-borne spores. In especially humid climates, algae is a very common problem and asphalt roof shingles seem to get it the worst.
Algae is found on siding that is shaded and stays damp. If exterior areas of your home are in the shade and hold moisture, they can develop this unsightly green algae. The length of time the algae has been on the siding determines how difficult it will be to remove the algae. Believe it or not, dirt can be the culprit even when everything else has been taken care of. Dirt is able to hold enough water to allow your algae infestation to take hold.
While algae stains on exterior walls are principally a cosmetic concern and can be cleaned, any building wall that stays damp and shaded may be at higher risk for hidden insect or rot damage.


Mold is a type of fungus that consists of small organisms found almost everywhere. They can be black, white, orange, green, or purple. Outdoors, molds play an important role in nature, breaking down dead leaves, plants, and trees. Molds thrive on moisture and reproduce by means of tiny, lightweight spores that travel through the air. You’re exposed to mold every day. Exposure to damp and moldy environments may cause a variety of health effects, or none at all. Some people are sensitive to molds. For these people, molds can cause nasal stuffiness, throat irritation, coughing or wheezing, eye irritation, or, in some cases, skin irritation. People with mold allergies may have more severe reactions. Immune-compromised people and people with chronic lung illnesses, such as obstructive lung disease, may get serious infections in their lungs when they are exposed to mold. Whether or not you're allergic to molds, mold exposure can irritate your eyes, skin, nose, throat, and lungs. For people sensitive to mold, inhaling or touching mold spores can cause allergic reactions, including sneezing, runny nose, red eyes, and skin rash. People with serious mold allergies may have more severe reactions, including shortness of breath. In people with asthma who are allergic to mold, breathing in spores can also cause asthma attacks. In small amounts, mold spores are usually harmless, but when they land on a damp spot in your home, they can start to grow. When mold is growing on a surface, spores can be released into the air where they can be easily inhaled. If you're sensitive to mold and inhale a large number of spores, you could experience health problems. Mildew is a surface fungi that can easily be identified as a patch of gray or even white fungus that is lying on the surface of a moist area.

Gloeocapsa Magma

This particular type of cyanobacteria is responsible for creating black stains and streaks on roofs. The bacteria accumulate over time as 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 and noticeability of these cyanobacteria are thought to be: 1) Rising humidity and temperatures combined with more and more bacteria spores promotes their spread with these favorable conditions. 2) 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 in the Midwest of the USA) than the paper/asphalt/ceramic shingles of the 1980s.

The bacteria are airborne. 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 stains will continue to worsen year to year. As the bacterial colony grows, gravity pulls it downward, resulting in the smear-like stain down roofs. Most experts within the subject area conclude the bacteria to be harmful, if left untreated, as the growth holds moisture within shingles causing premature aging, rotting, and/or granule loss.
The buildup of gloeocaspa magma on residential properties has led to earlier roof replacements, lowered property resale values, insurance companies canceling policies and increased utility costs as the black stained roofing draws in more heat.


Mosses are small flowerless plants that typically grow in dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients. Although some species have conducting tissues, these are generally poorly developed and structurally different from similar tissue found in vascular plants. Mosses do not have seeds and after fertilization develop sporophytes with unbranched stalks topped with single capsules containing spores.

As the moss thickens and grows on an asphalt shingle roof it can raise shingle up (much like a jack under a car). This debris promotes water buildup which makes the roof at risk of much more rotting and leaking. Moss can actually damage the asphalt shingle components leaving it to break down faster. Moss thrives in a damp, shady environment. For this reason it often occurs on the north side of a roof—since it receives the least amount of sun—or under overhanging trees that provide shade.


Lichens are a complex life form that exist from a symbiotic partnership of two separate organisms, a fungus and an algae. Is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. The dominant partner is the fungus, which gives the lichen the majority of its characteristics, from its thallus shape to its fruiting bodies.
It's a combination of algae and fungus and usually has a light, mint-green color. It doesn't trap as much water against the surface of the roof as moss, but it can be acidic and has strands that can penetrate into the shingles. Lichens and moss loosen the granules on the shingle surface exposing the asphalt and fiberglass base materials. The damage can reduce shingle lifespan.

Black Algae

Green or black algae, mold and mildew, lichen, and moss can all grow on your outdoor concrete and wood surfaces. ... Growths such as algae, mold and mildew can cause concrete sidewalks, driveways, decks or patios to become extremely slippery, creating a fall risk for you and your family.

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