What are the black roof stains?  Is it roof algae?

The black stains are actually an algae that is called Gloeocapsa  Magma

Why doesn’t my neighbor have the same problem?  Their shingles are much older than ours?

Older shingles didn’t used to have crushed limestone filler?

Why did they switch to limestone filler?  When they switched to a fiberglass matting for shingles …the shingles needed more weight.  

Were there any other reasons why they switched to limestone filler?  The cost of crushed limestone is much less than asphalt.

Does black algae harm the shingles Shingles have ceramic granules.  These granules help reflect the sun and protect the shingles from the damages that ultra violet rays produce.  The black algae prohibits the granules from reflecting the sun.  This causes the roof to heat up and the shingle to deteriorate quicker.  This can also drive up the cost of air conditioning your home in the summer. Holds moisture within shingles causing premature aging, rotting, and/or granule loss.

What is Roof Lichen? 

Roof Lichen is the hardest to remove without causing more damage to the roof.  The roof lichen latches onto the shingles with roots.  It is usually a greenish gray color. Lichen actually produces an acid that will disintegrate the ceramic granules.  This gives the lichen a better grip on the shingle and can turn the granules into dirt.  That’s why when you kill the lichen…you will see black spots where the lichen has eaten the granules below it. Lichen can survive in all temperatures.  It can be found where it is very hot down south, but can also be found in the extremely cold artic.

Does the algae create any health risks for my family?

It can be.  Very small spores can make it in to your home through an open window or air conditioner. Mold can trigger allergic reactions, coughing, sneezing, and trouble with asthma.  Remember the longer you let the algae grow the harder it is to eliminate.