Why are my roof shingles curling?

Short version: curling is usually age, heat or trapped moisture

Curling is most often a sign that shingles are wearing out. The U.S. Forest Service's roofing guide says that when shingles become old and worn out, they curl, split, and lose their waterproofing effectiveness.^[1] If your roof is 15 or 20 years old and the curling is spread across whole slopes, the likeliest cause is simply age.

Curling that shows up early, or only in one area, points to something else: a hot, poorly ventilated attic, moisture, or a problem with how the roof was put on. A roofer can tell the difference in a single visit, and the answer decides whether a repair is worth doing.

What curling looks like

Edges and corners lift away from the roof, either turning up (called curling) or humping in the middle with the edges down (called clawing or cupping). The shingles often shed granules, crack across the curl and show dark patches where the mineral surface has worn away. Look from the ground or with binoculars; there is no need to go up.

The usual causes

Age. Asphalt dries out and shrinks as it weathers. The Forest Service guide lists a lifespan of 15 to 25 years for 3-tab fiberglass shingles and 20 to 30 years for architectural shingles,^[1] so a roof near the end of that range curls because it has done its job.

Heat in the attic. Moisture in poorly ventilated attics promotes decay of the wooden roof sheathing and rafters, reduces insulation effectiveness, and can destroy the roof structure.^[1] A hot attic also cooks the shingles from below. Virginia Cooperative Extension says most homes should have a combination of a continuous ridge vent along the peak of the roof and continuous soffit vents at the eaves, and that in general a home should have approximately 1 ft2 of net vent opening for every 150 ft2 of ceiling or attic space.^[3] It adds that there are some exceptions, so always refer to your local building code. The Forest Service guide also says never to block off sources of roof ventilation, such as louvers, ridge vents, or soffit vents.^[1] See how to know if your attic is ventilated well.

Dark roofs and sun. The Department of Energy's Building America guide notes that lighter-colored asphalt shingles tend to last longer as they absorb less heat than darker shingles and are less likely to be damaged by prolonged heat.^[2]

Moisture and shade. Leaves on the roof retain moisture and cause the roof to rot, and algae can retain moisture in damp, shaded areas, causing deterioration.^[1] Trimming trees back from the house helps with that.

Installation problems. Shingles nailed too high, too low or with too few nails lift at the edges, and an unsealed shingle can be pulled up by wind. The Building America guide calls improper nailing a common error in shingle installation.^[2] Shingles laid in cold weather may also never bond: Owens Corning's warranty says its shingles contain asphalt sealant that requires direct warm sunlight for several days (Thermal Sealing) in order to seal properly.^[4]

Does curling mean a leak?

Not on its own, but it is a warning. Curled edges let wind get under the shingle, and nearby shingles are easily ripped off or blown away once one lets go.^[1] Where shingles are missing or torn off, the roof structure and the building's interior are vulnerable to water damage and rot.^[1] Check the ceilings under the affected slope and the attic for stains or damp insulation after rain.

Can curled shingles be fixed?

A few curled shingles on an otherwise sound roof can sometimes be re-secured or replaced by a roofer. Widespread curling cannot be fixed shingle by shingle. If the curling covers most of a slope, or the roof is near the end of its life, repair money is usually wasted and a roof replacement is the honest answer. The sibling guides help you weigh it: can a few missing shingles be replaced without a new roof and should I replace missing shingles or the whole roof.

If the curling follows a hot attic, ask the roofer to fix the ventilation too. Otherwise new shingles can curl for the same reason.

When to call a licensed pro

For the inspection and for any repair. Do not climb onto the roof to test curled shingles or press them down: roof work is dangerous, and curled shingles are brittle and easy to break underfoot. DPOR says that if the work you are considering is valued at $1,000 or more, a valid Virginia Contractor's License is required for the license category in which the contractor is to work.^[5] Virginia's contractor regulations define roofing contracting as the service that provides for the installation, repair, removal, or improvement of materials common to the industry that form a watertight, weather resistant surface for roofs and decks.^[6] Check the licence before you pay anything.

Getting help in Virginia

Loclis lists DPOR-licensed roofing businesses with their licence number and class. Browse roofing services or read more roofing repair answers. For prices, see how much it costs to replace missing shingles in Virginia.

When you are ready, describe the job once and licensed local roofers respond.