These days, one cannot go anywhere without hearing about “Green” building and “Green” lifestyles.  Well, here is a green roof that you certainly do NOT want.  One covered in the any of the the trifecta of yucky stuff; moss, lichen and algae.

A quick primer on roof maintenance below!


Roof moss like to thrive in damp, moist and shaded areas. Therefore, you will see more active growth on your shaded or north-facing roof planes.   Algae can actually put roots into the roofing materials and the areas between the individual shingles.  Also, it retains moisture and keeps the roof damp, promoting further growth and further adding to the degradation of the roofing materials.


Lichen is a fungus that exists in tandem with internal algae.  It receives food from the algae through photosynthesis, and provides protection for the algae.  Together they form a lichen.   They put out tentacle-like roots  deep into asphalt roofing, breaking down the roofing granules and creating pock-like marks and staining.


Algae lives on dust, pollen and organic debris.  It’s growth is also triggered by dampness and typically occurs on and around the granules that make up the surface of the roofing material.


Here’s a photo of a roof that has been hanging in the shade just a little too long!  When you think “green” you really don’t want your regular roof having uncontrolled organic substances on them!  What are the causes of this?  Well, it is a due to a number of things.  Tree branches could be too close to the house or even touching the roof creating the blockage of any sunlight or even a drop zone for tree stuff!  Sometimes it is this along with roofs on the North side of a home (again, no sun).  This one for sure has algae, lichen and certainly moss on it and in LARGE amounts!

How can you protect your roof from such intrusions?

There are several effective ways to prevent moss growth.  You can take away the shade and moisture and turn its environment extremely acidic or alkaline to kill the growth.

First: Remove any existing moss using a leaf blower or soft bristled hand brush.  If you have a composite or asphalt shingle roof, it is very important not to pressure wash it. Again – DO NOT USE A PRESSURE WASHER!  Pressure washing can remove the shingle granules which help protect the shingles and ensure a longer life span.

Second:  Apply something to kill the moss!  A “green” way would be to use Baking Soda or Vinegar.   By mixing Baking Soda with water or Vinegar and water and applying it directly, it will kill moss in all of the unwanted areas.  It may take a few months – but it is bound to work!  A second application may be necessary – so stick with it!

Remember, bleach and other chemicals can accelerate damage and erode metals.  Bleach will permanently kill plants that get sprayed.   Bleach can kill your surrounding plants and grass so if you must use bleach – be careful and protect the green stuff you want to keep!   Take precaution if this is the route you take.

Other methods:  Insert 6-inch-wide strips of zinc or copper under the row of shingling closest to the roof peak, leaving an inch or two of the lower edge exposed to the weather. That way whenever it rains, some of the metal molecules will wash down the roof and kill any algae trying to regain a foothold on your shingles.

– Mike

Roof Maintenance and the “Not-So-Good” Green Roof

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