Hail Damage Vs Blistering (5 Tips To Tell The Difference)

If you are looking at your roof after a storm and wondering whether what you are seeing is hail damage vs blistering, the distinction matters more than most homeowners realize. Adjusters deny claims every season because damage gets misidentified — blistering called hail damage, or actual hail impact dismissed as normal wear. Knowing what each one looks like, and why they happen, is the fastest way to protect both your roof and your claim.

This blog covers:

• Side-by-side visual comparison of hail damage vs blistering
• What causes each and how they differ structurally
• Why misidentification can cost you an insurance claim
• 5 key differences between the two
• When to call a professional for a definitive identification

Visual Comparison: What Each One Actually Looks Like

This is where most guides fall short. Before getting into causes and consequences, here is exactly what you are looking at on the shingle surface.

Hail Damage: Visual Characteristics

Hail impacts leave specific, identifiable marks that are distinct from natural deterioration:

• Sharp-edged impact craters: Hail hits with force and leaves an indentation with a defined edge, not a gradual softening of the surface.
• Circular granule loss: Granule displacement from hail impact is roughly circular and concentrated at the point of impact, often exposing the dark asphalt mat beneath.
• Random but patterned distribution: Hail strikes a roof in a spread pattern that reflects the storm’s direction. Damage appears across the field of the roof, not clustered near edges or penetrations.
• Corroborating metal damage: Vents, flashing, and gutters will show corresponding dents from the same event — these are independent evidence that confirms a hail storm occurred.
• Firm texture: Press on a hail impact site and the shingle surface beneath holds firm. The damage is at the surface, not underneath.

Blistering: Visual Characteristics

Blistering is an internal failure that looks very different on the surface:

• Raised, bubble-like formations: Blisters appear as dome-shaped swellings on the shingle surface, not depressions or craters.
• Soft centers: Pressing on a blister reveals a soft or hollow feel beneath the surface — the characteristic sign that gas or moisture is trapped inside.
• Random distribution: Blistering can appear anywhere on the roof and does not follow a storm-impact pattern. It may be concentrated where ventilation is poor or materials were improperly installed.
• No metal corroboration: Vents, gutters, and flashings will show no corresponding damage because blistering is caused by internal conditions, not external impact.
• Discoloration around the blister: Trapped moisture often leaves a slightly darker ring around the raised area as it seeps through the shingle surface.

Quick Reference Table

Why the Distinction Matters for Insurance Claims

This is the section most guides skip — and the one that costs homeowners money. Insurers cover hail damage as a weather event loss. They do not cover blistering because it results from manufacturing defects, improper installation, or inadequate ventilation, all of which are considered maintenance or workmanship issues rather than storm events.

When an adjuster visits after a storm, misidentification can go two ways. If blistering is mistakenly presented as hail damage, the claim will be denied when the adjuster recognizes the internal nature of the failure — and the denial may flag your claim history. If actual hail damage is dismissed as blistering, you lose coverage for a legitimate loss.

The best protection against both outcomes is an independent inspection by a HAAG certified contractor before the adjuster arrives. HAAG certification specifically trains inspectors to distinguish storm-caused damage from manufacturing and installation failures using documented methodology that insurers recognize. For a roof inspection checklist on what to document before your adjuster visit, our guide covers the full process.

Understanding Hail Damage

Hail damage occurs when hailstones impact the roof surface, causing dents, granule loss, and in severe cases cracking or fracturing of the shingle fiberglass mat. The severity depends on hailstone size, wind speed, and roof age. Damage may not be visible from the ground and can lead to leaks months after the storm if left unaddressed.

Long-term, unchecked hail damage leads to increased moisture penetration, mold growth, reduced energy efficiency from compromised insulation, and a shortened roofing system lifespan.

Understanding Blistering

Blistering occurs when gas or moisture becomes trapped within the roofing material and expands during heat exposure. It is almost always tied to one of three causes: improper installation, inadequate attic ventilation, or low-quality materials. Blistering weakens shingles and reduces their waterproofing effectiveness over time.

The result is reduced protection against leaks, accelerated wear, and premature shingle failure — none of which are covered under a standard storm damage claim.

5 Tips to Tell the Difference Between Hail Damage and Blistering

While both issues affect shingle performance and can eventually lead to leaks, they come from completely different causes. Knowing how to spot the difference helps you avoid misdiagnosis and potential insurance claim denial.

1. Identify the Cause

Start by considering what triggered the damage. Hail damage results from a specific weather event, while blistering develops from internal roofing conditions such as trapped moisture, manufacturing defects, or poor ventilation.

• Storm related origin: Hail damage follows a documented weather event
• Installation or material issue: Blistering forms due to heat and moisture buildup
• Insurance factor: External storm damage is typically insurable

2. Examine the Surface Appearance

Look closely at the shape and texture of the affected area. Hail creates impact marks, while blistering creates raised bubbles.

• Circular craters: Hail leaves defined impact depressions
• Granule displacement: Hail knocks protective granules away
• Raised bubbles: Blistering forms soft domes without surface dents

See our guide on granule loss on shingles for more on how progressive surface deterioration develops differently from storm impact.

3. Check the Distribution Pattern

Damage patterns provide important clues. Hail damage usually aligns with the storm’s direction, while blistering appears randomly.

• Consistent impact zones: Hail often affects one roof slope more heavily
• Metal corroboration: Dented gutters or vents support hail evidence
• Random clustering: Blistering often appears in poorly ventilated sections

4. Consider the Timing

Think about when the issue appeared. Hail damage is sudden and noticeable after a storm, while blistering develops gradually.

• Immediate visibility: Hail damage appears right after severe weather
• Weather documentation: Storm reports can confirm hail size
• Progressive deterioration: Blistering worsens slowly over time

5. Evaluate the Repair Approach

The solution required can also help identify the problem. Hail damage is typically addressed through shingle replacement and insurance documentation, while blistering requires correcting underlying ventilation or material issues.

• Storm repair focus: Hail damage often involves insurance claims
• Root cause correction: Blistering requires ventilation improvements
• Material upgrade: Higher quality shingles reduce blister risk

When to Call a Professional for Identification

If you cannot determine with confidence whether you are looking at hail damage or blistering, do not guess before contacting your insurer. A professional assessment protects your claim either way.

Call a professional when:

• You see surface anomalies after a storm but cannot confirm whether they are impact craters or blisters.
• Your insurer has scheduled an adjuster visit and you want independent documentation beforehand.
• You have a mix of apparent damage types and need a clear written assessment.
• Your claim has been denied and you believe the damage was misclassified.

We’re proud to serve homeowners in Evansville, IN, and surrounding communities including Louisville, KY with professional storm damage inspections and accurate damage identification. Our HAAG certified inspectors know exactly how to document hail damage in a way that holds up with insurance adjusters — and how to identify blistering for what it is so you are not left filing a claim that cannot succeed. Contact Embry’s Roofing today for a free inspection and get a clear answer before your adjuster visit.