Roofing shingles curl in different ways. Each type of curling pattern results from different causes. Types of causes of curling shingles include improper care or storage of the shingles before installation, improper installation, wear and defective materials, including the shingles themselves.
Curling can develop on the corner, in the middle or across the entire shingle. "Fishmouthed" roof shingles are those that curl in the middle of the shingle as a result of moisture buildup or ventilation problems. Walking across the roof to remove ice or conduct other repairs is a cause of shingle curling in the corners of shingles, as is extreme heat or cold. Poor or defective interior insulation, flashing or other roofing materials can cause curling across the bottom edge of a shingle.
The way the shingles are curled provides good evidence to the cause of the curling. According to InspectAPedia.com, most curled shingles develop in a pattern across a large section or the entire roof. Rarely are only a few shingles curled. If the shingles are already 20 years old, the entire roof might need to be replaced.
Curled shingles might indicate other structural problems in a home or building, including excessive moisture from a wet basement or inadequate attic ventilation. Once shingles are curled, additional damage to the shingles might occur, which can further weaken a roof and surrounding structures. In this case, a complete building or home inspection might be necessary. Curled shingles might require partial or total roof replacement, which is an expensive endeavor.
Walking a lot on shingles might cause damage that leads them to curl, so minimize the amount of time spent on top of the roof. Similarly, regularly scraping ice buildup off shingles in the winter can also result in wear to the shingles that later results in curling. Do not attempt to pull off, repair or replace curled shingles without the know-how or proper tools, as further shingle and roof damage might occur.
Store shingles according to manufacturer's directions before installation. Install shingles properly, paying special attention to weather conditions and any existing problems with the building or roof structure. Inspect the roof regularly for signs of shingle problems, especially after extreme hot or cold temperatures or after a strong storm or heavy ice or snow buildup.