Thread: What all causes shingle discoloration

This roof is 10 years old. It is not in the shade anytime during the day. The attic ventilation could be better but it does have decent vent.
Otherwise the shingles seem to be in good shape. Any suggestions?

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Organic growth maybe????

I know that shingle manufacturers now include an algicide treatment on their shingles.

Was there dew on the roof at all, the ground/road looks damp in the picture.

We have been in a bad drought for over a month. However, what you can't see in the picture, on the other side of the road is a rather large river.

It is usually mildew that dries and turns black. Typically where the sun does not directly hit the home. You will see some where one side looks 15 years old and the other 3-5 yrs. When your on the roof see where the sun moves over it and you will see a pattern for mildew growth.

From the Web:

Unsightly black stains on shingles are often mistaken for fungus, mildew, dirt or oil, but are actually caused by a hardy type of algae. This common problem has increased during the past 20 years, indiscriminately settling on rooftops from coast to coast. Dark algae streaks are visible when algae cover roofing granules¿the ingredient in a shingle that gives vibrant colors of white, cobalt blue or hunter green, for example, to rooftops.

For more see:

Pabco Roofing - Products

I tried something on the house we bought up here, to see what it does and how it works out.

There is a company which 'cleans' shingle roofs with a bleach/water/degreaser solution, which is sprayed out at a low pressure (less than garden hose pressure) through a section of PVC with what looked like (and I am sure it was) a half circle sprinkler head on the end. The spray was minimal, yet you could see it building up on the shingles and running down the roof.

After this set and dried out, they went around and rinsed it off with the same sprayer and plain water from a garden hose (this time at garden hose pressure, they hooked it up to the garden hose).

I was surprised that the solution cleaned as thoroughly as it did (the roof looks great and has NO stains on it). They give a 5 year guaranty too, and will come back at anytime within that 5 years and retreat at no cost (no bull, one of my new neighbors had this done to his house and they were coming back to retreat his (after 3 years, there was limited staining re-appearing) for no charge, so I figured there was not much to lose.

I figure our roof has less than 5 years left on it (it's a 9:12 slope, so it drains very well), so what did I have to lose. The staining was algae - the bleach kills it, the water dilutes the mix, the degreaser is for longevity.

I asked about the solution and they were hesitant to tell me, but I did get out of them that it was not just bleach and water, but the degreaser is what allows them give the 5 year warranty. Don't know what the mix ratio was, couldn't get that out of them.

Talk about roof slope, one neighbor has a 14:12 slope and another has a 20:12 on part of their roof, and another is even steeper on the front section. Talk about a 'water slide' like those kids built.

Algae-- agreed...

This does not mean they are defective or they are bad. Algae by itself is not a cause for replacement .

I've seen people clean the staining off the roofing material with the cleaner made for decks.

Its the same thing I think they use on older fencing to remove the gray before the fencing is stained with color.

It does smell like it has a high concentration of bleach in the material.

Rick

I always thought that algae was what is described below. But I would like to be proved wrong.
I honestly think ,Mold, Mildew, Fungus fit into the same moisture induced areas but I have only seen algae on the surface of water.


Algae (singular alga) are groups of relatively simple living "AQUATIC" organisms that capture light energy through photosynthesis, using it to convert inorganic substances into organic matter.

Mildew refers to certain kinds of mould or fungus. In Old English it meant honeydew (a substance secreted by aphids on leaves, formerly thought to distill from the air like dew), and later came to mean mildew in the modern senses.[1]


Powdery mildew growing on a leaf. The ladybird beetle is a Psyllobora species which feeds on the mildew.The term mildew is often used generically to refer to mould growth. Moulds can thrive on any organic matter, including clothing, leather, paper, and the ceilings, walls and floors of homes with moisture management problems. Moulds often live on shower walls, windowsills, and other places where moisture levels are high. There are many species of moulds. In unaired places, such as basements, they can produce a strong musty odor.

What most horticulturalists and gardeners call mildew is more precisely called powdery mildew. It is caused by many different species of fungi in the order Erysiphales. Most species are specific to a narrow range of hosts, and all are obligate parasites of flowering plants. The species that affects roses is Sphaerotheca pannosa var. rosa.
Another plant-associated type of mildew is downy mildew. Downy mildews are caused by fungus-like organisms in the family Peronosporaceae (Oomycota). They are obligate plant pathogens, and the many species are each parasitic on a narrow range of hosts. In agriculture, downy mildews are a particular problem for growers of potatoes, grapes, tobacco and cucurb

Originally Posted by Rick Hurst

I've seen people clean the staining off the roofing material with the cleaner made for decks.

Its the same thing I think they use on older fencing to remove the gray before the fencing is stained with color.

It does smell like it has a high concentration of bleach in the material.

Rick

There is actually a product at home depot just for cleaning roofs. It does not contain bleach. I have used it and it was applied just as Jerry said.

Spray & Forget, No Rinse, Roof and Siding Cleaner - Removes Green & Black Algae, Mildew, Moss, and Lichen Stains from External Surfaces

Here is another one: Roof Cleaner from JNK Products

I did an inspection on a roof years back. The homeowner was having a big party so before the party, they pressure cleaned their roof. They cleaned off all of the granules from almost every shingle. Needless to say, another recommendation for replacement! It was a six year old roof!

Barry:

A good source for roof condition inspections is:

Haag Engineering Co. Publications - Product Catalog

Aaron

Aaron referenced Haag Engineering... this is from that Haag publication, page 22. (see attachment).

Wayne, from MSN Encarta, My bold,

Algae vary greatly in size and grow in many diverse habitats. Microscopic algae, called phytoplankton, float or swim in lakes and oceans. Phytoplankton are so small that 1000 individuals could fit on the head of a pin (see Plankton). The largest forms of algae are seaweeds that stretch 100 m (300 ft) from the ocean bottom to the water’s surface. Although most algae grow in fresh water or seawater, they also grow on soil, trees, and animals, and even under or inside porous rocks, such as sandstone and limestone. Algae tolerate a wide range of temperatures and can be found growing in hot springs, on snow banks, or deep within polar ice.

I am not an expert on this and I didn't even stay at Holiday Inn Express, but this definition certainly leaves room for the stuff growing on roofs to be algae.
Jim

Originally Posted by Barry Grubb

This roof is 10 years old. It is not in the shade anytime during the day. The attic ventilation could be better but it does have decent vent.
Otherwise the shingles seem to be in good shape. Any suggestions?

I stayed in a Holiday Inn Express!!

2 things: there is a type of algae that grows on the north side of roofs. I see this a lot. I looked it up on the internet about a month ago. It's not much of an issue. The stuff at Home Depot probably works.

Also, are there pine trees anywhere around there? Turpentine is made from parts of pine trees. Here in east Texas (pine tree capital), the needles will stain if left on shingles for any length of time. My guess is that a little rain, a little sun, a little turpentine on the asphalt...voila...staining.

All of the above information has not been redeemed reliable by any socially-redeeming individual.

Bruce

Perhaps you should consider the addition of Zinc strips as a better solution than cleaning products. Zstop

Originally Posted by Michael Larson

Perhaps you should consider the addition of Zinc strips as a better solution than cleaning products. Zstop

Except that most of those have an effective range of about 10' down the roof. Meaning that you would need to install them every 10' down the run of the roof slope.

I visited the certanteed shingle manufacturing site in MA a few years ago.

They recognized the algae problem years ago and now include a small amount of copper granules in their mix to prevent it, so you won't see this in their newer shingles.

I think they have been doing this for 10 years. If anyone knows the
exact date of this process change, we could tell how old (or at least age)the roof is, by the algae on it?

The primary species of algae being observed is Gloeocapsa Magma. This type of algae is contained in and transported through the air, and tends to collect and grow upon roofing structures.

You have a virtual buffet on your roof for these organisms to thrive. The shingles that are produced today have crushed limestone embedded into the asphalt as a filler for weight (not the granules you see on top). These shingles hold moisture and organic "bacteria food" material longer than the shingles of 20 years ago. Additionally, these particular algae enjoy the limestone as a food source.

Now as far as algae resistant shingles, that is exactly what it means, resistant not proof. If you check most shingle manufacturer warranties the shingle may be guaranteed for 30 years but the algae resistance is only guaranteed for anywhere from 5 to 20 years. You are going to get algae eventually it is just a matter of when.

Here is a very good YouTube video explaining what those black streaks are. YouTube - The Truth About Roof Cleaning and Roof Algae Fog and Dew are primary sources for moisture to keep these buggars alive.

Hope this helps explain things.

Pat Motz
Owner
The Cleaning Doctor