Curling, Cracked or Lifting Shingles: What Each One Means

Curling shingles usually mean the roof is aging or the attic is overheating, cracked shingles usually mean the asphalt has dried out and become brittle, and lifting shingles usually mean the seal strip has let go, often after wind. Each one tells you something different about your roof. A few damaged shingles on a younger roof are a repair, but widespread curling or cracking across several slopes means the roof is near the end of its life.

Curling shingles: cupping and clawing

Shingles curl in two ways, and roofers name them differently. Cupping is when the edges of a shingle turn up, so the shingle looks like a shallow dish. Clawing is when the edges stay down and the middle of the shingle rises, so the corners look like they are gripping the roof. Both mean the shingle is no longer lying flat, and a shingle that does not lie flat does not shed water or resist wind the way it was designed to.

The most common causes we see on Livingston County roofs:

• Age. As the asphalt loses its oils over many summers, the shingle shrinks and distorts.
• An overheated attic. Poor ventilation bakes the shingles from below in summer and lets moisture condense under them in winter. Curling that is worse on one area of the roof often points to a ventilation problem above that part of the attic.
• Installation problems, such as high nailing, too few nails or shingles installed over an old layer.
• Moisture held against the shingle by moss, debris or shade on north-facing slopes.

Curling on a roof that is less than ten years old is not normal wear. It usually means a ventilation or installation problem, and it is worth finding out which before it shortens the life of the whole roof.

Cracked shingles

Cracks that run across a shingle, or split it at the edge, are usually a sign of brittleness. Michigan roofs go through dozens of freeze-thaw cycles every winter, and an older shingle that has lost its flexibility cannot keep up with the expansion and contraction. The result is thermal cracking, which tends to show up on many shingles at once. Older three-tab shingles, common on 1990s and early 2000s subdivision homes across Howell, Genoa and Oceola Townships, are especially prone to it.

Cracks can also come from a shingle being walked on in cold weather, from a falling branch or from hail. Impact damage looks different: it shows up as round bruises or broken spots rather than straight lines, and usually only on the slopes that faced the storm. Our post on hail and wind damage explains how to tell storm damage from age.

Lifting shingles

Each asphalt shingle has a strip of sealant that bonds it to the shingle below once the sun warms it. That seal, together with the nails, is what keeps the wind from getting underneath. When the seal fails, the shingle can lift and flap in the wind. Eventually it creases along the nail line, or tears loose entirely.

Lifting usually comes from one of these:

• Wind strong enough to break the seal, especially at rakes, ridges and eaves
• Shingles installed in cold weather that were never hand-sealed and did not bond until spring
• Old sealant that has dried out and lost its grip
• Nails driven too high, which leaves the bottom of the shingle free to move

After a windstorm, look for shingles that look out of line, show a lighter or darker strip where they have lifted, or have a visible crease across them. A creased shingle has lost its strength even if it settles back down.

What about granules in the gutters?

Granules are the colored, sand-like coating on asphalt shingles. They protect the asphalt from the sun. A small amount of granules in the gutters after a new roof is installed is normal, because loose extras wash off. Steady granule loss on an older roof is a sign of aging. If you see bare, dark patches on the shingles, or your downspouts are washing out piles of granules after every rain, the shingles are losing their sun protection and will start curling and cracking faster.

Repair or replace?

A handful of lifted or cracked shingles from a single storm, on a roof that is otherwise in good shape, is usually a roof repair. The shingles are replaced, sealed and nailed correctly, and the roof goes on doing its job.

The picture changes when the damage is widespread. Curling or cracking across several slopes, heavy granule loss, sealant that no longer holds the tabs down and a roof past twenty years in this climate all point the same way. Replacing scattered shingles on that roof is spending time and effort on a surface that is wearing out everywhere. We go through this in more detail in our guide to how long a roof lasts in Michigan.

What we do differently on a new roof

Most of the causes of curling, cracking and lifting are things a good installation prevents. On every roof replacement, we install Owens Corning Duration shingles with the SureNail reinforced nailing strip, nail to the manufacturer's wind pattern, hand-seal where cold weather calls for it and correct the attic ventilation so the shingles are not cooked from below. As an Owens Corning Platinum Preferred Contractor, we register the complete system warranty in your name.

Shingle damage questions

Can curling shingles be flattened or glued down?

Gluing down a few curled tabs can buy a little time, but it does not reverse the aging or fix a ventilation problem. Widespread curling means the shingles are reaching the end of their life.

Are curling shingles a sign of a leak?

Not by themselves, but curled shingles let wind-driven rain and ice dam water get underneath more easily, so leaks often follow.

Why are my new shingles not lying flat?

Shingles installed in cool weather may not seal flat until warm weather arrives. If they still look uneven after a summer, the deck, nailing or ventilation should be checked.

How many damaged shingles is too many to repair?

There is no single number. The age of the roof, how many slopes are affected and the condition of the deck matter more than a count.

Find out what your shingles are telling you

We inspect every slope, photograph the damage and tell you in writing whether you need a few shingles replaced or a new roof. The inspection is free for homeowners in Howell, Brighton, Hartland and across Greater Southeast Michigan, and our inspectors are HAAG Certified. Call On Top Roofing at (810) 588-3933 or request your free estimate.