Dirty Roof Myth Busters No.9


“Zinc strips protect a roof from roof algae.” This is a myth. First let’s cover how zinc strips work. Zinc strips are long strips of sheet metal coated with zinc. They vary in width with a typical width of 3 foot.  They are attached along the peak of the roof. When it rains, a slight amount of zinc dissolves from the strips and coats part of the roof, partially inhibiting algae and fungus growth. This part is true. This principle is commonly seen on roofs with galvanized (zinc coated) flue pipes penetrating the roof. The shingles down slope of the pipe look streak free while the surrounding shingles have black streaks and stains. Unfortunately the protective effect of the zinc strips is good for only a few feet down slope from the strips. This can be illustrated by the photo below. So the truth is zinc strips helps to protect a small part of the roof from algae. But by no means protects the entire roof. Economically it would be more cost advantageous to periodically have the entire roof Economically it would be more cost advantageous to periodically have the entire roof professionally treated than to have zinc strips installed.

Zinc strips

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