Curled, cracked or blistered shingles come down to four causes: age, a damp attic, a factory defect or hail. The shape of the damage points to the cause. The cause decides who pays.
A few bad shingles can be fixed. When the damage runs across the whole roof, roofing contractors say replace it.
What does it mean when shingles curl?
Age, most of the time. Cupping is when the middle of each tab sinks and the edges rise. Clawing is the opposite: the corners turn down and under.
Both come from the asphalt shrinking as it ages, on the top surface for cupping and the bottom for clawing, according to a roofing engineering paper quoted by InspectAPedia, a building inspection reference site. Old organic-mat shingles cup more than today’s fiberglass ones. Both do it.
A new roof that cups is another story. InspectAPedia calls that unusual and points to shingles laid over a wet deck, or over an old layer of curled shingles. Call whoever installed it.
Can a bad attic make shingles curl?
It can add to it. Air Vent, a vent maker, lists curling or cracking shingles among the signs of a poorly vented attic, and an IKO bulletin ties poor ventilation to curling, blistering and faster aging.
A 2010 insurance trade article explains the chain. Damp house air rises into the attic and condenses on the underside of the roof boards. The boards stay wet. The shingles on top distort.
Nobody we read has measured how much ventilation matters, and the loudest voices sell vents. Still, it is the cause you can fix. Before you reroof, look in the attic for rusty nails, black plywood or wet insulation, then check how much venting a Sioux Falls attic needs.
Why do shingles crack in a Sioux Falls winter?
Cold and movement. Shingles grow and shrink with the temperature, and a tab that bridges the gap between two shingles in the row below gets pulled both ways. If the sealant strip holds tighter than the shingle is strong, the shingle splits. Home inspectors call it thermal splitting.
Sioux Falls tests that hard. The airport averages about 97 days a year that freeze and thaw, and 162 nights at or below freezing (NOAA, 1991 to 2020).
Install day counts as well. A 2002 industry paper says the asphalt roofing makers’ trade group and most fiberglass shingle makers caution against installing at or below 40 F, because cold shingles crack in handling. That damage may not show for a year or two.
Then there is hail. In the lab impact test behind Class 3 and Class 4 ratings, a crack counts as a failure and a dent does not. Cracks that appear right after a storm belong with what hail damage looks like on a roof.
Are blisters on shingles a problem?
Small ones are cosmetic, by the makers’ account. Blisters are bubbles in the asphalt that pop and leave pits, sometimes down to the mat.
A 2000 industry journal article quotes the trade group’s definition: they form from trapped air and moisture when the shingle heats up. A 1999 ASTM paper traced them to damp mats or under-cured resin at the factory. Some contractors blame hot attics. InspectAPedia calls that theory speculative.
The 2000 article says small rash blisters that never open should not threaten the roof. Large blisters that open and bare the mat are a different matter, and InspectAPedia says those roofs should be replaced.
Popped blisters get mistaken for hail. Hail leaves shallow marks, often in a pattern, and dents the metal vents and gutters. Blisters sit at random, with steep-sided pits and no dented metal.
Is it age, the attic, a defect or hail?
Match what you see to the likely cause. A contractor confirms it on the roof.
| What you see | Likely cause | Who might pay |
|---|---|---|
| Cupped or clawed tabs across an old roof | Age: the asphalt shrinking | You. A warranty covers defects, and policies exclude a lack of maintenance |
| Curling on a newer roof, with rusty nails or black plywood in the attic | Attic moisture and poor ventilation | You. Shingle warranties exclude ventilation damage |
| Straight splits over the joints in the row below | Thermal splitting, or a cold install | Ask the installer, then the shingle maker |
| Small blisters spread at random | Moisture or resin from the factory | The shingle maker, if it hurts performance |
| Fresh cracks after a storm, with dented metal | Hail | Your insurer. Never the warranty |
Is it a warranty claim or an insurance claim?
A factory defect goes to the shingle maker. Storm damage goes to your insurer. Age and a damp attic are yours.
GAF’s current warranty shows how the fine print reads. It covers manufacturing defects that hurt how the shingles perform. It leaves out damage from poor ventilation, hail, foot traffic, bad nailing, and shingles that were never hand-sealed in cold weather. Owens Corning and IKO leave hail out too.
Its claim rules catch people out:
- Tell GAF within 30 days of noticing the problem. Telling your contractor does not count.
- Do not repair or replace first, or the claim may be denied.
- Expect to send photos and sample shingles at your own cost, with proof of the install date.
On GAF’s lifetime shingles, the payout shrinks after the first 10 years. Labor is no longer covered, and the shingle value drops with age: at 25 years, GAF’s share is cut in half.
Insurance has limits of its own. Policies do not cover damage from a lack of maintenance, and one South Dakota carrier pays only actual cash value for wind and hail roof losses once the roof is 10 or more years old. Read how a roof claim works in South Dakota before you call.
Should I repair or replace curled shingles?
Repair a few. Replace the roof when curling or cracking covers all of it, which is the rule roofing contractors give.
Age settles close calls. National charts give 3-tab shingles about 20 years and architectural shingles about 30, and the other end-of-life signs are in how long a roof lasts in South Dakota.
Stay off a curled roof. InspectAPedia calls cupped shingles fragile and warns against walking on them, so look from the ground or a ladder, take dated photos, and let the contractor do the walking.
Questions about curling and cracked shingles
Can curling shingles be repaired?
A few curled shingles can be replaced. When curling runs across the whole roof, roofing contractors treat it as a sign the roof needs replacing.
Does homeowners insurance cover curling shingles?
Not when age or a damp attic caused it, because policies exclude damage from a lack of maintenance. Shingles cracked or torn by hail or wind in a storm are a claim.
Are blisters on shingles hail damage?
They are different. Popped blisters are random pits with steep sides, while hail leaves shallow marks and dents metal vents and gutters.
Does a shingle warranty cover curling?
Only if a manufacturing defect caused it. GAF’s warranty excludes damage from poor ventilation, bad nailing and hail, and you must report a claim within 30 days of noticing it.
Why are my new shingles cupping?
Cupping is unusual on a new roof. InspectAPedia points to shingles laid over a wet deck or over an old layer of curled shingles, so call the installer.
Get a quote
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