Dirty Roof Myth Busters No.1


The state of Illinois and the rest of the mid-west region are being invaded and most people don’t even realize it yet. Have you noticed any rooftops that have ugly black streaks and stains? Most folks living in this area think those streaks and stains are a number of things including:

  • A sign that the asphalt shingles are aging
  • The shingles are defective and the granules are falling off
  • Tar or creosote seeping out of the shingles
  • Jet fuel
  • Dirt
  • Acid rain

These are all myths! The truth of the matter is that air born algae (mold) lands on the roof and feeds on the material in the asphalt shingles. The technical name for the algae is Gloeocapsa Magma. It grows mostly on the north and west facing roofs which receives the prevailing moisture and shade. The Gloeocapsa Magma is a microscopic organism which is not visible with the naked eye. This hungry organism feeds off the limestone material found in asphalt shingles and multiplies on all sides of the roof. However since the north sides make the most ideal breading ground for the algae, it multiplies and spreads most rapidly across the roof’s north surface. The dense areas of the algae communities are evident by the black streaks and ugly stains which are a protective sheathing that the algae excrete.

This air born algae is more prevalent as you travel south in warmer and more humid climates. Over the years the algae has been spreading across the states. That is why it seems to be more and more noticeable here in the mid-west region. The effects of the algae are not only unsightly but very costly if not treated. If your roof is infected by algae or other organisms such as moss or lichen, have a certified roof cleaner (non-pressure spray system) inspect it as soon as possible.

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