How can I fix curled shingles?

Fixing curled shingles can be done as a temporary repair if the curling is minor and limited to a few shingles, but widespread curling indicates roof replacement is needed. For isolated curled shingles that are still flexible and not cracked, choose a warm day above 60 degrees when asphalt is pliable. Carefully lift the curled portion without breaking it, and apply a generous amount of asphalt roofing cement or roofing sealant underneath with a putty knife, spreading it under the curl and onto the shingle below. Press the shingle down firmly for at least 30 seconds to ensure good adhesion. To keep it flat while curing, place a heavy flat object such as a brick or board on top for 24 hours. If the shingle will not stay down, you can add a small roofing nail just above the curled area, then cover the nail head completely with roofing cement to prevent leaks. This repair may last 1 to 3 years. However, if shingles are brittle, crack when bent, or curling is widespread across the roof, repair is not advisable because curling signals that shingles have lost their oils due to age or poor attic ventilation and have lost waterproofing ability. In that case, plan for full replacement and correct ventilation issues.