What causes curled shingles?

Shingle curling happens on the shingle corners. They tend to curl upwards or under. Curling shingles result in other problems like mold and leakage. Let’s delve into the possible causes of shingle curling:

High nails

When the nails that secure the shingles sit up, the roofing material curls. The nails sit up due to contraction and expansion, inching themselves upward. Nailing patterns need to be properly set up during installation.

Lack of back coating

Each shingle has an adhesive strip which adheres the tabs to the shingle row. The adhesive may fail to line up properly, especially if the shingles are not installed according to the manufacturer’s instructions. The sealing strip prevents curling or lifting in high winds.

Poor or no ventilation

Moisture accumulates in the attic as a result of moisture released into the home. Moisture from outside also results in accumulation of moisture in the attic. Usually, when the attic is well ventilated, the moisture is swept away by air flow. If your roof has poor or no ventilation, moisture builds up in the attic. There is no way for the moisture to leave the attic. It condenses, damaging the framing and decking. It eventually gets trapped between the shingles and roof underlayment, causing the shingles to curl. A poorly ventilated attic results in high temperatures. This reduces the strip adhesive’s effectiveness and may even cause major damage which will require complete roof replacement.

Improper nailing/skip nailing

If your installer deviates from the recommended nailing pattern, for instance using 3 nails per shingle (instead of 4), the shingle slips downwards, making it curl. The installer may skip nails to save time. Unfortunately, you will need to contact him to come and re-do his job. When a nail is driven into the sealing strip, the effectiveness of the seal on the strip is reduced. Thermal cycles – hot days and cold nights – cause the nail to back out. The shingle tab lifts, parting from the seal, resulting in shingle curling.

Defects in roofing products

Some of the common defects in roofing products include inadequate adhesion of grit and bituminous coating, lower rates of deterioration than stipulated in warranties, inadequate sealing strips, and poor quality substrate.

Shingle overs

During a shingle over, the main aim is to have the subsequent layer in line with the original one. There is a likelihood that the newer layer will not seal properly. They can move and twist in high winds, causing them to lift. If the nails used are not long enough, the shingles will lift.

Thermal cycles

Continuous wet and dry cycles cause shingle curling. Moisture may accumulate under the roof shingle making it bend. This weakens the roofing material making it bend upward.

Winter shingle curling

During winter, snow or ice may accumulate on your roof. This lowers the shingle’s temperature. The protruding surface bends upwards. The top surface contracts, while the bottom remains flat as there is some amount of heat coming from the house or attic. The bottom side of a shingle is placed against the roof, absorbing indoor heat. The temperature difference between the 2 surfaces causes the shingle to bend upwards.

Life expectancy

Sometimes, shingle curling may be due to the fact that your roof has reached its life expectancy. After ruling out all the above-discussed factors, and putting your roof’s age into consideration, it may be time for a new roof.

Shingle curling is a sign of worse things to come. Knowing what causes it will help you identify the problem and fix it as soon as possible.  If you think that your shingles might be damaged or deformed, contact your trusted roofing company in Irving, Reilly Roofing & Gutters. We are here for you and your roof.


Reilly Roofing & Gutters
320 Decker Drive. #100
Irving, TX75062

Phone: (972) 770-4806
Payment Method: All Major Credit Cards and Checks

Call Now