Hail Damage vs. Blistering
Insurance adjusters are trained to point at hail impacts and call them “heat blisters” to deny your claim. Learn how to physically diagnose the fiberglass mat to prove functional damage.
The Diagnostic Index
An asphalt shingle is like an M&M. It has a hard candy shell (the granules), a chocolate center (the asphalt), and a nut inside (the fiberglass mat). To get an insurance payout, you must prove the storm broke the nut.
1. The “Heat Blistering” Excuse
During the manufacturing process, tiny pockets of moisture or gas can get trapped inside the asphalt. When your roof gets incredibly hot during the summer, these gas pockets expand and literally pop out of the top of the shingle. This is called Blistering.
Because blistering creates a small, circular bald spot where the granules used to be, it looks exactly like a hail strike from 10 feet away. Adjusters love blistering. It is a manufacturing defect, which means it is excluded from your insurance policy.
2. The Mat Bruise: Undeniable Proof of Hail
Hail comes from the sky at high velocity. It is an impact event. It does not pop out from the inside; it punches down from the outside.
When a hailstone hits a shingle, it crushes the granules into the asphalt. More importantly, the kinetic energy fractures the fiberglass mat inside the shingle. This creates a “bruise.”
The Thumb Test
If an adjuster points to a mark and says it is blistering, walk up and press your thumb into the center of the spot. A blister will feel hard and rigid because the fiberglass mat is intact. A hail strike will feel soft, yielding, and spongy—exactly like a bruised apple. A soft mat means functional damage, which means they must pay.
3. Why Granule Loss is Not Enough
Many homeowners call their insurance company because they see piles of colored sand (granules) washing out of their downspouts. They assume this proves storm damage. It doesn’t.
Shingles shed granules naturally every day. Granule loss is considered “cosmetic” and is excluded by almost every modern insurance policy. You must instruct your contractor to search the roof for localized, circular impacts that caused an actual fracture. Do not let your contractor argue “granule loss” to the adjuster; they will lose the argument instantly.
4. How to Correct the Adjuster On-Site
If you are on the roof or watching the adjuster take photos, and you hear them dismiss the damage as blistering or mechanical marring, you must object immediately and on the record.
“I respectfully disagree with classifying this as a blister. A blister displaces granules outward and leaves the mat rigid. If you feel this impact, the fiberglass mat is fractured and yields to pressure. This is a functional bruise indicative of a high-velocity downward impact. Please ensure your report notes that the mat is fractured.”