A.The differences between
organic and fiberglass shingles are considerable and affect the
quality rating of each material.
Organic shingles are composed of five components. The mat is
made from wood fibers and recycled paper. This mat is saturated
with a special saturant-grade asphalt. It is then coated
on both sides with a harder, stabilized coating asphalt.
A surfacing of mineral granules, usually ceramic-coated
crushed rock, is added to protect the asphalt from the
ultraviolet rays of the sun and to provide a decorative
surface. Finally, a backcoating of particulate material,
usually sand, slag, talc, or limestone, is added to keep the
shingles from sticking together and from staining during
Fiberglass shingles use only the coating-grade asphalt,
which saturates a fiberglass mat and holds the surfacing. The
granules and the backcoating are the same as for organic
In the past, when all asphalt shingles were organic, the
quality of a particular shingle was judged by its weight and
the length of its warranty. This is no longer considered an
accurate basis. There are considerable differences in both the
quality of the asphalt coating and the weight of the mats for
both organic and fiberglass. Some tests have shown that a
mid-weight shingle with a strong mat is more durable than a
heavy shingle with a weak mat.
Despite warranty claims ranging from 15 to 25 years, there
is evidence of premature failures of both types of shingles.
The best assurance of quality is tear resistance.
Minimally, roofers and builders should look for compliance
with the ASTM Standard D3462 for fiberglass shingles, which
calls for a minimum tear strength of 1,700 grams, using an
Elmendorf Tear Tester. There is no standard for organic
shingles, but most will exceed 2,000 grams of tear