Q: Why are the corners of my shingles turning up? A: Corners of shingles turning up is refered to as Curling and it is generally caused by excess moisture attacking the underside of the shingle. Inadequate ventilation causes the entrapment of heat and moisture in the attic. This will eventually penetrate the roof deck and cause the shingles to curl. Improving air circulation within the attic space can stop the progress and rectify the situation if the curling is not too severe. In some rare instances, curling can reveal itself only under cold weather conditions. This would be refered to as winter curling. The corners of the shingles will slightly curl up from the roof deck when cold, then lay flat again during warmer weather. This is especially prevalent during damp winter conditions when frost forms on the top surface of the shingles. This cooling on the top surface will cause the shingle to contract while at the same time the underside of the shingle in contact with the roof receives a certain amount of passive heat from the attic space. The variation of temperature between the top side and underside of the shingle will result in some minor curling. This does not affect the shingle�s durability and effectiveness to shed water.