Why are some shingles on this roof flat and others are distorted?
a. Because of variations in thermal distribution in the roof structure.
b. Shingles on this roof are from two separate batches.
c. Shingles in the lower part of the roof are in the shade more of the time.
d. Distorted shingles were stored at the bottom of excessively tall stacks for an extended period of time before installation.