The term ‘curling’ is applied to shingles that have corners turning up and it is commonly caused by moisture on the underside of the shingle.
Many of my clients ask me how moisture can get on the underside of a shingle when the roof system is fairly new and there are no leaks. The main culprit in such cases is inadequate ventilation, which I talked about here. Since a lack of ventilation traps heat and moisture in the attic, this moisture eventually penetrates the roof deck and leads to shingles curling.
The only solution that can stave off further curling or warping is adding vents to help improve the air circulation within the attic space; this should only be done by a certified roofer who understands building science, as cutting into the plywood could compromise the entire roof system and create leaks.
As we head into winter season in Toronto, many homes will experience ‘winter curling’ of shingles. This is when the cool temperature on the top surface of a roof will cause shingles to contract, while the underside of the shingles experiences heat from the attic. This variation in temperature will cause the shingles to slightly curl up from the roof deck during the winter, and then lay flat again once the weather warms up. Watch for this condition especially during damp, cold weather when frost forms on the top surface of shingles. This condition is not threatening to the roof system as shingle durability can withstand seasonal contracting/expanding, and it does not is affect the shingle’s effectiveness to shed water.
It’s only when shingles are constantly exposed to heat and moisture from a poorly ventilated attic that they curl prematurely and begin to deteriorate. Let Archer Roofing contractors inspect your roof to check for shingle curling before Toronto winter season hits and protect your roofing system from premature deterioration. Call us at 416-427-2437.