How to fix shingles that are curling?

Fixing shingles that are curling depends on whether the curling is minor and isolated or widespread. For a few shingles with minor curling where the shingle is still flexible, you can perform a temporary repair that may last a few years. Choose a warm day above 60 degrees when shingles are pliable. Gently lift the curled section, being careful not to crack it, and apply a generous amount of asphalt roofing cement underneath using a putty knife, spreading it beyond the curled area. Press the shingle down firmly and hold for 30 to 60 seconds. Place a heavy weight such as a brick on top for 24 hours to keep it flat while the cement cures. If the edge will not stay down, you can add a single roofing nail just above the curl line, then cover the nail head with roofing cement to prevent leaks. However, if shingles are brittle, crack when bent, show cupping across many areas, or the curling is widespread, repair is not effective. Widespread curling indicates the shingles have lost their oils due to age, typically 18 plus years, or that the attic has inadequate ventilation causing heat buildup. In that case, replacement is required, and you must correct ventilation by adding soffit and ridge vents before installing new shingles to prevent recurrence.