Blistering shingles are asphalt shingles whose surface bubbles up and later pops, leaving pockmarks that may show the mat underneath. Why they bubble is usually heat, and what to do starts in the attic. On modern roofs it most often shows up in the first year or so and is usually tied to heat: gases escaping from overheated new shingles, often on a roof with poor attic ventilation. It is not hail damage, and it rarely leaks right away, but widespread blistering can shorten a slope’s life. This page is general information; your roofer and the shingle manufacturer have the final word on your roof.
On this page: Signs · Causes · Hail or blisters? · Fixes · Basis · When to call
Signs of blistering
- Raised bubbles on the shingle surface, often clustered on one slope or one area.
- Small round pockmarks where bubbles have popped, with dark asphalt or mat showing.
- Granules collecting in gutters below the affected slope.
- Usually on a newer roof, and often on the sunniest slopes.
What causes shingle blisters
- Overheated new shingles. Volatile gases escape from hot asphalt and lift the surface. A roof deck that bakes because the attic cannot breathe makes this more likely.
- Poor attic ventilation. Too little intake at the eaves, blocked soffits, or mixed exhaust vents that short-circuit airflow. See our guide to attic ventilation.
- Too much roof cement under shingles. Owens Corning’s cold-weather bulletin warns that excess cement can blister shingles.
- Manufacturing moisture or gas. Less common on modern shingles, but a question for the manufacturer if the roof is young.
Blisters or hail? How to tell from the ground
| Clue | Blistering | Hail |
|---|---|---|
| Timing | Shows up over months, often in the first year | Appears after a specific storm date |
| Shape | Round pockmarks, often in clusters | Random impact marks across the slope |
| Soft metals nearby | No dents | Dents and spatter on gutters, vents and AC fins |
| Ridge caps | Usually fine | Often damaged, per IBHS |
- Scan the slopes with binoculars for clusters of round pockmarks.
- Check gutters, downspouts and AC fins for dents that would point to hail.
- Write down when you first saw the marks and how old the roof is.
- Look in the attic on a hot afternoon, from a safe spot on the framing. Stifling heat and blocked soffit vents support a ventilation cause.
Stay off the roof.
Fixing blistered shingles
| Repair | When it fits |
|---|---|
| Monitor | A few small, isolated blisters. |
| Correct the attic ventilation | Almost always, because heat is the usual driver. |
| Replace affected shingles or slopes | Blistering is widespread or exposing the mat. |
| Ask the manufacturer about coverage | The roof is young and blistering is extensive. |
Fixes that do not help: coating or painting over blisters, and labeling blisters as hail to try to get a claim paid.
What the sources say
InterNACHI’s inspection series (Part 35) says blisters on modern shingles usually come from poor roof ventilation, typically appear within the first year, rarely cause leaks because each course has two layers of shingle, and can shorten the life of a slope when large and widespread. Owens Corning’s cold-weather installation bulletin warns against excess asphalt cement because it can blister shingles. The 2021 IRC, section R806.2, sets attic ventilation at 1/150 of the vented area, or 1/300 when specific conditions are met, and R806.3 requires at least 1 inch of air space between insulation and the roof deck at eave vents. We did not find a primary manufacturer or NRCA document on blister causes, so treat cause as something to confirm on your roof.
When to call a roofer
Call if you see bubbles or pockmarks spreading, especially on a roof under a few years old. The first step is usually an attic check, because a ventilation fix protects the next roof too. Related guides: granule loss, nail pops, attic frost, and the full roof problems guide.
Ask for a blister and attic check
Integrity Roofing and Painting is veteran-owned and family-run since 1990, an Owens Corning Platinum Preferred contractor with 650+ Google reviews. We check the shingles and the attic together and give you the findings in writing. Colorado Springs area: (719) 488-2800 or a free inspection. Denver metro: (303) 209-0152 or a free Denver inspection. Austin: (512) 610-5897 or a free Austin inspection. We reply the same business day.
Sources: InterNACHI, Mastering Roof Inspections: Asphalt Composition Shingles, Part 35; Owens Corning technical bulletin, Cold weather shingle installation; IBHS, Is it hail damage?; 2021 IRC Chapter 8, sections R806.2 and R806.3 (UpCodes).
