Shingles present an uneven surface and do not lie flat. Physical distortion or buckling can be seen in shingle tabs.
Shingle tabs curl up at the corners.
Network or series of fine crack lines can be seen on surface of shingles.
Bubbles or bumps appear under shingle surface.
Inadequate ventilation of attic area. Water vapor from the home gravitates toward and accumulates under the roof deck. Condensation occurs in winter when warm, moist air comes in contact with the cold underside of the roof deck, even when there is a vapor barrier. This condensation can result in buckling, curling, surface cracks and/or blistering.
Install proper ventilation that allows air to circulate freely under the roof deck and carry away water vapor before it can condense. Several methods are available that will provide natural draft ventilation from bottom to top of attic space: