Our shingles are bulging and curling

Q. As per our house engineer’s recommendation after closing in 2005, a new roof was installed on our “new” cape to replace the flat old brittle roof. Within a year, shingles began to bulge and curl, and the roofer returned to repair them. The bulging and curling shingles returned in early 2006, and the problem has continued to worsen. The roofer says it’s not his responsibility any longer, and suggested that we contact the shingles’ manufacturer, which we’re doing, since it’s still within the warranty period. The bulging and curling occurs only on the south-facing roof of both our house and garage. There are gable vents on the east and west sides of both the house and the garage. There’s no direct access to the house attic, but the garage attic is readily accessible, not finished, and used for storage. Why is this happening, and what can we do about it?

A. I regularly see roofs like what you described, and recently learned that Underwriter’s Laboratories and Consumer Reports downgraded asphalt shingle roofs, stating that claims of 30 to 40 years and even “lifetime” are exaggerations. South-facing shingles are subjected to much greater expansion and contraction due to the extremes of the sun’s heat and radiation. I’ve often commented here that roof membranes and shingles need to breathe, need to ventilate and cool. If they’re baking in the sun under incredible stress, they will separate, curl, and fail.

Your roof has no overhang, just a rain gutter at the edge that is barely attached and leaning forward. This tells me that the design of the house was wrong, that there are no soffits with a surface area under the eves that would allow air to flow upward. That’s problem No. 1. Problem 2 is that the end venting only works when the wind comes from that direction, since it can’t flow through the entire attic and relieve heat at the other end. If insulation between the rafters of your finished sloping ceiling was stuffed tightly in place, without an air space just below the roof shingles, then air cannot flow. The shingles will overheat and react like leaving a fish in the sun.

Roofs are systems. They aren’t finishes. Unless you have insulation in the right place, toward the room, with an unobstructed air channel space above, clear airflow at a high point, since heat rises, calculated venting area large enough to get the air moving, your shingles will keep failing. Ridge vents, by themselves, aren’t enough. You’ll need a vent fan to draw air through the attic space. Solar vents will avoid electric costs, and may be your best choice.

©2013 Monte Leeper. Readers are encouraged to send questions to yourhousedr@aol.com, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.