Blistering Roof Shingles

Why Do Shingles Blister?

Blistering shingles are a common problem with asphalt shingles. There are two main reasons that asphalt shingles blister.

• Trapped Moisture in the Shingles — Sometimes during the manufacturing process moisture can get trapped within the shingle itself. If the shingles on a roof have trapped moisture, they are highly likely to start blistering. Why? Because as the sun heats up the shingles the trapped moisture heats up as well and can cause blisters to rise up on the shingle.
• Poorly Ventilated Roofs — Roofs that do not have an adequate ventilation system in place can get too hot for shingles. If a roof that is poorly ventilated gets too hot, the shingles can blister because of the intense heat.

Popped shingle blisters photo courtesy of InspectAPedia.com - used with permission

Are Blistering Shingles Bad?

This question could be answered with both a yes and a no answer. Let us explain.

No. As long as the blisters on the shingles keep their granules they will not cause a problem for the roof or longevity of the roof.

Yes. Like all blisters there comes a time that they will surely pop. When blisters pop on shingle roofs the granules become dislodged leaving the asphalt unprotected from the UV rays of the sun. When this happens that area of the roof is prone to continue to lose more and more granules. With time and natural weathering these popped blister areas can in fact lead to leaks and roof damage.

Prevent Blisters From Popping

If you already know that some of the shingles on your roof are blistering, here are some tips to help prevent them from popping.

• Be careful not to walk on the blistered shingles. Blistered shingles can pop when they are disturbed by foot traffic.
• Falling debris. Some homes are surrounded by trees. If you have trees that continue to drop pine cones, acorns, limbs, or other types of debris onto your roof, they could cause blisters to pop. removing these trees could be very beneficial to the life of your roof.
• Blisters can also pop because of hail storms. However, there is not much you can do about preventing hail from hitting your roof and ruining your asphalt shingles.
• Another method of prevention is to replace the asphalt shingles before they pop. This could be a costly repair based on how many shingles are blistered.

Distinguishing Blisters from Hail Damage

Distinguishing blister damage from hail damage can be confusing to some. We hope to lightly touch on some of the differences between the two in this section of the article.

One of the ways to distinguish the differences is by paying close attention to the damage pattern on the roof. Is the damage scattered? Is the damage only on one slope? Take close observation to the area, the slope, and overall direction of the damaged shingles.

For example, a shingle roof that has been damaged due to blisters being popped by foot traffic will also have parts of the rooftop that have un-popped blisters. In comparison, a roof that is damaged by hail will have much more uniform damage and on a particular slope because of the wind direction during the hail storm.

• For more information or photos of damaged shingles and the various causes State Farm has created a great pdf file to learn from.

Professionals Interviewed:

We would like to thank Daniel Friedman from Inspectapedia.com for contributing his knowledge to help us write this article.

Other Resources Used:

Shingle Blistering Article: A North Carolina General Contracting Company - pattoncontracting.com

PDF File about inspecting asphalt shingles by State Farm - statefarm.com

Hail damage on a roof vs blisters: what each looks like

Up close, the two leave different marks. A popped blister is a small, crater-like pit with crisp edges where a bubble in the asphalt burst, and the hollow underneath is dark asphalt. A fresh hail hit is a roundish spot where granules were knocked away, and if you press it with a thumb it may feel soft or spongy, like a bruise on fruit, because the mat underneath has fractured. Older hail hits turn dull and darker as the exposed asphalt weathers.

The rest of the house tells the story too. Hail big enough to hurt shingles almost always dents the softer metals first: gutters, downspout elbows, roof vents, the fins on the air conditioner, and the metal around chimneys and skylights. Torn window screens and chipped paint on the side that faced the storm are other signs. If none of those show any marks, blisters are the more likely cause.

Timing helps an insurer. Note the date of the storm, look up local hail reports for that day, and photograph dents on metal alongside the marks on the shingles. Blisters build up slowly over seasons of heat; hail damage appears overnight.

Granule loss on shingles: normal shedding or a problem?

Some granule loss is expected. A brand-new roof sheds loose surplus granules in its first heavy rains, and you will see them in the gutters and at the downspouts. That should taper off quickly. A roof near the end of its life also sheds more as the asphalt dries out and lets go of them, which is part of normal wear.

What isn't normal is loss in patches. Round bald spots scattered at random point to hail. Small pits in clusters point to popped blisters. Scuffed bare areas near the ridge or around vents suggest foot traffic. Streaks of bare mat on one slope can come from a pressure washer, which shingle makers say should never be used on their product. Once the black asphalt or the fiberglass mat shows, sunlight breaks it down quickly and that spot will leak sooner.

When you find granule loss, match it to a cause before deciding what to do. Patchy blister loss on a young roof is a warranty conversation with the maker. Hail loss is an insurance conversation. Even, all-over thinning on an older roof is a sign to start planning a replacement.

Curling shingles and blisters: the shared cause

Blistering and curling often show up on the same roof, and for the same reason: heat and moisture trapped under the shingles. When an attic can't breathe, the deck and shingles bake from below in summer, the asphalt dries out faster, and the shingle edges pull up into a cup or the corners claw down. Moist air leaking up from the house adds to the trouble in winter.

You can look for it yourself from the attic hatch. Warning signs include soffit vents buried under blown-in insulation, bathroom or kitchen fans that empty into the attic instead of outdoors, frost on the underside of the deck on cold mornings, and dark or damp patches on the wood. On a hot afternoon, an attic that feels like an oven compared with the outdoors is another clue.

Fixing the airflow won't flatten shingles that have already curled or heal blisters that have popped, but it slows the damage on the rest of the roof and protects the next one. Many shingle warranties also require proper ventilation, and a maker may deny a blistering claim if the attic falls short of it.

Questions people ask

Are blistering shingles covered by the manufacturer's warranty?

Sometimes. Makers often call blistering cosmetic, and they may deny a claim if the attic lacks the ventilation their instructions require. If blisters appear early and keep spreading, file a claim with photos and the original paperwork and let the maker inspect.

Does homeowners insurance cover blistered shingles?

Usually not on their own, because blistering comes from manufacturing or heat, not a sudden event. If a hailstorm or a falling limb damaged the roof, that damage may be covered even on a roof that also has blisters.

Should blistered shingles be replaced?

Only if the blisters have popped and bare spots are spreading, or leaks have started. A few unbroken blisters don't need work. A roofer can swap out a handful of bad shingles, but widespread popped blisters usually mean planning for a new roof.

How do you know if a roof has hail damage?

Look first at soft metal: dented gutters, vents and air conditioner fins. On the shingles, look for random round spots of missing granules that feel soft when pressed. A roofer or adjuster can confirm it by marking the hits inside a test square on each slope.

This guide was updated in October 2026 with new sections and the questions people ask most.