Atlanta Roofing: Article About Living Roof Stains
Hot and humid summers can be hard on a roof. Atlanta Roofing problems are more likely to occur under the intense solar glare of a July day than in the relatively mild month of December. Of all the common summer problems, the large stains that cover so many roofs in the area are perhaps the most unsightly.
Two of the most common organisms to grow on asphalt shingles are moss and a type of blue green algae called Gloeocapsa Magma. Both types of growth require very moist air in order to thrive, but moss prefers shady conditions. It often grows beneath a tree or on the north side of a house. Blue green algae, on the other hand, thrives in bright sunlight.
Moss is also likely to be a thicker layer, and it may seem fuzzy. Moss may grow in disconnected patches all across the roof. The algae Gloeocapsa Magma will discolor the shingles. It may seem to run down the roof in streaks or spread as a single large stain. Algae are especially visible on light colored shingles while dark shingles help to mask it.
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Probably the most important difference between the two organisms is that moss will cause a roof to deteriorate, but algae are merely a cosmetic problem. They are a very prominent cosmetic problem, however, so no matter which type of organism is growing on a roof, it should be addressed.
Both moss and algae share a common weakness: certain metals. They cannot grow around copper or zinc. Even the runoff water that picks up molecules of those metals will impede their growth. Roofers have used this fact in a couple of ways. A metal strip along the ridge of the roof will prevent any growth for a distance further down the slope. For most roofs, 2 to 4 inches on either side is sufficient. Lately, manufacturers have even begun making shingles with flecks of copper embedded in the asphalt. This covers the entire roof in safe and natural algae protection. It is an option worth considering when replacing a roof in hot, humid areas like Georgia.
If the current roof is still in good shape, it is possible to wash away moss or algae. Use bleach water or a special wash that is produced to target the stains. It is best not to use a power washer because they can damage shingles. It is likely that the growth will come back, but periodic washing should handle the problem.