No. 4
1993-01-19
Printable version

DISTORTIONS ON ASPHALT SHINGLES

Occasionally, asphalt shingles may distort slightly along their leading edge to create a small bump somewhere along the length of the shingle. Typically, the remainder of the shingle lays flat and looks fine in all other respects. These bumps may be more noticeable on certain roofs because of slope, sunlight, shingle colour, viewer angle, etc. These distortions do not diminish the life of the shingle and, providing they are less than approximately 1/2" (12 mm) in height, do not lead to leakage, blow-off, or other shingle failure problems. Often, the shingles' uneven appearance is caused by:

•  raised fasteners (nails or staples),

•  dirt, leaves, or other contaminant on the shingle sealant,

•  uneven deck, underlayment felt, or old shingle layers,

•  shingles damaged or bent prior to application.

These "fishmouths", as they are known in the industry, are merely aesthetic phenomena which can be easily repaired. The most common repair method used is a hot melt adhesive to glue the distortion down to the underlying shingle, thereby rendering the shingle flat. The sealant bond on the affected shingle should be broken first, and the repairs are most effective when done during mild (but not too hot) weather conditions.

Next Bulletin: Asphalt Shingle Test Standards

Previous Bulletin: The Use of Underlayment With Asphalt Shingles

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