What Are Blistering Shingles and How Do They Form?

Blistering shingles cause the surface of asphalt or fiberglass roof tile to bubble up in some areas. It often occurs due to heat from sunlight or extreme temperatures, which causes the asphalt to expand and then contract when it cools down again.

The process repeats until eventually there is enough pressure from trapped air bubbles underneath the surface that cause it to breakthrough. At this point, it will form blisters on top of the tile’s surface. Blistering typically starts at one location on a roof and then spreads as long as the underlying cause continues.

Shingle Blistering vs. Hail Damage Blister

Shingle blistering and hail damage blistering are two different but similar conditions. The primary difference is definitional. Shingle blisters form on the top coating of a roof’s protective finish. Hail damage is caused by large masses of ice falling from the sky before melting, and these melt droplets can freeze upon contact with roofs.

When a roof has been damaged by ice repeatedly, this causes protection layers to peel off or detach altogether, leaving rough surfaces that can allow water to seep through.

“Both blistering types are risks during installation. They could potentially result in shingles lifting or breaking off entirely, which can lead to leaks and other substantial damage.”

What Causes Asphalt Shingles to Blister?

A variety of different factors can cause roof blisters:


One common cause of blistering is damage due to hail or other natural disasters. If the roof has sustained significant damage, water may pool in one place and blister that section of shingle. Even something as small as a fallen leaf could lead to blistering because it could create an obstacle on the way down, leading to blistering on certain pieces of shingle.

Inadequate Ventilation

Asphalt shingles blister on the surface if the shingle is not well ventilated. Poor ventilation will also cause the blistering to be more profound. If water penetrates through an unventilated shingle, it can blister the asphalt, causing the granules to blister.

Asphalt Shingle Manufacturing Defects

According to InterNACHI, “weathering accelerates the deterioration of shingles that have manufacturing defects” (1). An asphalt shingle manufacturing defect can be identified with cupping and curling deformities, fishmouth fault, degranulation, and thermal cracking.

On asphalt shingles, blistering can occur when the granules of mineral material are pressed out during installation. As the mineral granules act as an adhesive for the asphalt shingle, blistering can occur when they are removed.

Improper Installation

At times, asphalt blistering is the result of improper installation. When asphalt shingles are not properly installed, water can leak underneath them and blister the surface upon heating. The blistering process prevents the shingle from being waterproof, which makes blistering detrimental to your roof. 

How Do You Fix Roof Blisters?

Blisters on the roof can be repaired in two ways – repairs or replacements.

Many experts believe that blisters should be left alone unless they show indicators of more significant damage. There are, however, several situations in which you should repair the blister:

  • The blistering area is peeling away.
  • The membrane has a crack in it.
  • The blister is close to the seam and could cause it to open up. 
  • The blister is located in a high-traffic area.

There are several ways to repair blistering shingles. It can be done by cutting away the membrane until you reach an area where the membrane is still firmly adhered to the roof to heal a blister. You will then need to purchase a blistering shingle coating that can be applied to the blistering area. This coating will seal and cover the blister without removing the old blister from the roof.

In extreme cases, blistering shingles may need to be removed from the roof. The company that installed your roof should be contacted because only they can do the replacement. The contractor will need to scrape away the blister, replace the granules that blistering has caused to be removed, and then apply an emulsion. If blistering is more severe, like blistering caused by hail damage, the roof may need to be replaced.

If you’re not sure whether you need roof repairs or not, you can refer to Everything You Need To Know About Home Roof Repairs.

Preventing Blistering Shingles

There are a few things you can do to keep blisters from forming on your roof. Here are some great tips on how you can prevent blistering shingles:

  • Roof inspections on a regular basis: You should always ensure that your roof is properly sloped and clean your roof at least twice a year. Check if gutters and downspouts are free of debris and properly connected to the ground.
  • Sealants: Keeping your roof dry and free of moisture is critical. You should ensure that your shingles are not exposed to snow and ice for extended periods by using a primer first and then applying a good quality sealant.
  • Proper attic ventilation is essential: Finally, you should try to maintain a good level of ventilation on your roof so blistering does not occur due to moisture.

Is Roof Blistering Covered by Insurance?

Roof blistering is not covered by insurance. Currently, there is no insurance policy that covers this. This is referred to as wear and tear. You may be able to obtain coverage under warranty, but if not, you will have to pay for the repair out of your pocket.

However, you can always have a professional roofing expert inspect your home before meeting with an insurance adjuster to see if there are any other damages that insurance may cover.

FAQs About Blistering Shingles

What does blistering on shingles look like?

Blistering shingles appear as large bumps that seem to bubble up from the roof’s surface.  

What makes the roof blister? 

The blistering shingles can occur when the shingle is exposed to high heat for an extended period of time. It can also be caused by moisture that gets trapped beneath the layers of the roof, which causes blistering.

How does blistering damage my roof?

When blistering occurs on your roof, it causes significant damage to the shingles and can cause other issues as well. Blistering will prevent the natural granules from coating your roof and keep it from reflecting heat, which can lead to ice dams and further heat-related damage.

Is blistering shingles on a roof bad?

Blistering shingles are not necessarily bad. If blistering occurs, it is often referred to as blistering shingle syndrome. This means that blistering is a symptom of some type of underlying problem with the roof structure, such as loose shingles or inadequate ventilation.

What causes shingles to fail?

There are a few reasons that contribute to the failure of shingles. Some of these include poor installation, weather conditions, and underlying problems with the roof’s structure that blistering may indicate.

What is Inadequate Asphalt Coating?

The application of asphalt coating requires a shingle to be heated, which increases its flexibility before being coated. If this process is not done correctly, blistering can occur due to the shingles not being flexible enough to follow the contour of the roof.

What happens if blistering shingles are not replaced?

If blistering is not repaired and allowed to continue, it can lead to permanent roof damage. This damage may then lead to leaks that can do further damage to the roof’s structure.

What is the cost of blistering shingle replacement?

The average cost of blister replacement varies depending on factors such as the length of time blistering has occurred, the severity of blistering, and the size of the roof.

Can blistering be removed?

Blistering can not typically be removed. A new coating can either be applied over the blister itself, or blistering can be scraped. When blistering is severe, you will need a roof replacement. 

Can blistering shingle syndrome be prevented?

Yes, blistering can be prevented by maintaining a roof properly and doing regular inspections of it. If blistering is already occurring on a roof, it can be prevented by adequately repairing blistering right away. Blistering should not be allowed to continue, or the problem will get worse and possibly cause other issues on your roof.

Final Notes

Blistering shingles need to be addressed as soon as possible. This blistering can lead to leaks and other damage, which can cause further problems down the road if they are not repaired immediately.

Whether you’re in the market for a new roof or not, it’s worth understanding how blistering shingles affect your home and what steps to take if they’re on your roof. If you notice blistering on your roof, be sure to contact us at Atlanta Roof Repair today. Our team of roof experts will be able to identify any potential underlying issues and replace your roof if needed. 



  1. International Association of Certified Home Inspectors https://www.nachi.org/asphalt-comp-shingles-part35-89.htm


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