The Nasty Black Marks On Your Roof – Dealing With Roof Algae

Aug 04, 2014

If you don’t think roof algae is a problem, then think again. The nasty looking black marks on your roof and siding are a common enough problem to be discussed even in the Washington Post Health and Science section. They say this in an article titled – Roof algae: The prehistoric organism that streaks your shingles.

Black streaks running down your roof aren’t a sign that the asphalt shingles are dissolving or that you need a new roof. Rather, you have roof algae. The organisms arrive on the rooftop as either spores or clumps of cells. If they land on the north side of the roof, where the sun is less harsh and moisture more plentiful, the algae will have a good environment to multiply, spreading in a delta down the slope of the roof.

There are various types of algae, but the familiar dark stains that form on roofs and siding panels are often caused by the species known as Gloeocapsa magma. The algae doesn’t stand out much, but after some time, their outer layer starts to harden and develop a darker color, forming visible black spots on the surface.

Most people think the black streaks caused by roof algae are mostly a cosmetic issue, but these harmless (albeit ugly) dark spots can eventually cause your roof and shingles to deteriorate faster. Woodbridge, NJ siding and roofing specialists strongly suggest getting rid of roof or siding algae before it causes problems.

Fortunately, dealing with roof algae is easy, especially if they it’s just starting to form. Using zinc or copper strips can prevent more algae from growing, but it will not get rid of existing dark spots. It may be tempting to use a pressure hose to wash off algae streaks, but Carteret NJ vinyl siding experts strongly advise against it, since strong blasts of water can push a panel or two out of place. Not to mention it wastes a lot of water.

A gentle scrubbing with a mixture of bleach and water is often more than enough to get rid of the streaks. However, extra care must be taken when using bleach on the shingles or siding. A strong concentration may cause further discoloration on certain roofing or siding materials.

As with most problems, preventing the problem in the first place is a lot better than dealing with it. Preventing roof algae from accumulating is just a matter of cleaning the roof and shingles on a regular basis once a month.

(Excerpt taken from – Roof algae: The prehistoric organism that streaks your shingles)

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