Direct Answer
Small roof blisters do not always require immediate repair. On some commercial roofing systems, small, intact blisters can be monitored if the membrane remains watertight, the blister is stable, and there are no signs of cracking, exposed reinforcement, moisture intrusion, or separation at seams. However, blisters that rupture, grow, weaken the membrane, expose underlying materials, or contribute to seam separation should be evaluated for corrective action.
For commercial property owners in Florida, the right decision depends on the roof system, the blister’s size and location, the condition of the surrounding membrane, and whether moisture is trapped beneath the surface. A qualified commercial roofing professional should evaluate questionable blisters before deciding whether to monitor, repair, or investigate a larger roof-system problem.
The National Roofing Contractors Association’s technical guidance, summarized in Professional Roofing, explains that closed blisters may sometimes be left undisturbed, while ruptured blisters, exposed reinforcement, fatigue cracks, and blisters in high-traffic areas may require repair. Johns Manville also notes that occasional membrane blistering can indicate a minor application error, while severe blistering across a roof may signal more significant problems.
Who This Applies To
- Commercial property owners
- Property and facility managers
- Commercial real estate investors
- Building engineers and maintenance teams
- Condominium and HOA boards responsible for common-area roofs
- Owners managing commercial roof maintenance and capital budgets
Not for: This guidance is not a substitute for a roof-specific inspection, manufacturer repair instructions, or warranty requirements. Blisters on different roof systems can have different causes and repair requirements.
1. Understand What a Roof Blister Means
A roof blister is a raised bubble or localized swelling in the roofing membrane or roof covering. It can develop when air, moisture, or other gases become trapped between roofing layers or between the membrane and its substrate.
Blisters can occur on built-up roofing, modified bitumen, spray polyurethane foam, and some other roofing systems. Their significance depends on the materials involved and the condition of the surrounding roof.
Possible causes include:
- Moisture trapped beneath the roofing membrane
- Insufficient adhesion between roofing layers
- Installation over a damp substrate
- Voids between membrane layers
- Adhesive-related application problems
- Existing moisture intrusion
A raised area alone does not establish that the roof is leaking. The important question is whether the blister is stable and intact or whether it indicates a developing defect.
2. When Small Blisters Can Be Monitored
Small blisters may be suitable for monitoring when a qualified professional confirms that the surrounding roofing system remains in satisfactory condition.
Monitoring may be appropriate when:
- The blister is small and stable.
- The membrane surface remains intact.
- There are no visible cracks around the blister.
- The blister has not separated an adjacent seam.
- There is no evidence of active leakage.
- The surrounding membrane is not deteriorating.
- The blister does not create a significant traffic or maintenance hazard.
The Roofing Practices Manual published by the Roofing Contractors Association of British Columbia recommends leaving small, unbroken blisters in certain bituminous roof systems undisturbed and recording their locations so changes can be identified during future inspections.
That guidance is system-specific. It should not automatically be applied to every TPO, PVC, EPDM, modified bitumen, or spray foam roof.
3. When a Blister Should Be Repaired
A blister deserves closer attention when it begins to compromise the roof covering or creates a risk of water intrusion.
Warning signs include:
- A blister that has ruptured or developed a crack.
- Exposed membrane reinforcement or underlying roofing materials.
- Fatigue cracks forming around the blister.
- A blister that is growing or changing noticeably.
- Separation at a nearby seam or lap.
- Damage in an area frequently accessed by maintenance personnel.
- Evidence of water intrusion or deteriorated materials underneath.
According to Professional Roofing’s discussion of NRCA blister guidance, repair should be considered when blisters occur in high-traffic areas, when the membrane has ruptured, when reinforcement is exposed, or when fatigue cracking develops. Repair also should be considered when blistering has separated a seam by approximately one-third or more of its width.
Do not deliberately puncture a blister simply to determine whether it contains air or moisture. Opening a blister without preparing a proper repair can create a pathway for water intrusion.
4. Evaluate the Blister’s Size, Location, and Condition
Size matters, but it should not be the only factor in deciding whether to repair a blister.
| Observed Condition | Potential Concern | Recommended Response |
|---|---|---|
| Small, intact, stable blister | Potentially localized membrane separation | Document and monitor if appropriate for the roof system |
| Growing or increasingly raised blister | Possible progressive separation | Arrange a professional evaluation |
| Cracked or ruptured blister | Potential water-entry point | Arrange appropriate corrective work |
| Blister with exposed reinforcement | Reduced protection of underlying materials | Evaluate and repair as appropriate |
| Blister near a seam or flashing | Potential separation of a critical roof detail | Inspect the surrounding detail and membrane |
| Numerous blisters across the roof | Possible widespread adhesion or moisture problem | Assess the overall roof system |
There is no single blister diameter that determines whether every commercial roof requires repair. The acceptable response depends on the roof material, the defect’s condition, the manufacturer’s guidance, and the building’s circumstances.
5. Determine Whether Moisture Is Trapped Beneath the Roof
One of the most important questions is whether a blister is associated with moisture in the roofing assembly.
A qualified professional may investigate:
- Moisture beneath the membrane
- Wet or deteriorated insulation
- Previous leak locations
- Nearby open seams or failed flashings
- Signs of recurring water intrusion
- Similar blisters in adjacent areas
Where appropriate, a professional may recommend moisture-survey methods or selective roof openings to establish the condition of the underlying materials.
Do not assume that every blister contains water. Equally, do not assume that an intact surface proves that the roof assembly beneath it is dry.
6. Consider Florida’s Heat, Rain, and Storm Exposure
Commercial roofs in Florida experience intense sunlight, high temperatures, heavy rainfall, humidity, and seasonal storms. These conditions make regular roof inspections important, particularly when blisters are located near seams, penetrations, drainage areas, or frequently accessed equipment.
After severe weather, look for changes such as:
- Newly ruptured blisters
- Fresh punctures or tears
- Separated seams
- Loose flashing
- New interior leaks
- Damage caused by rooftop equipment or debris
Document any significant changes and arrange a professional assessment when the condition suggests that the roof’s watertight integrity may be compromised.
7. Do Not Ignore Widespread Blistering
A few isolated blisters can represent a different problem from extensive blistering throughout a roof.
Widespread blistering may indicate:
- Installation over wet materials
- Moisture within the roofing assembly
- Adhesion problems across a larger area
- Repeated deterioration of the roof membrane
- A need for more extensive corrective work
Johns Manville’s commercial re-roofing guidance distinguishes occasional blistering, which may reflect a minor application issue, from severe blistering across a roof area, which can indicate significant problems. The guidance emphasizes identifying the cause before determining the corrective scope.
If blistering is widespread, repeated spot repairs may not address the underlying issue. A broader roof assessment may be needed to determine whether localized repairs, restoration, or replacement is appropriate.
8. Understand How Blisters Affect Roof Warranties
Before authorizing repairs, review the roof’s warranty and contact the manufacturer or authorized contractor when required.
Check:
- Whether blistering is addressed by the warranty.
- Whether the roof system has specific repair requirements.
- Whether repairs must be performed by an authorized applicator.
- Whether the manufacturer must be notified before work begins.
- Whether the proposed repair materials are compatible with the existing system.
Johns Manville’s guarantee information describes conditions and exclusions that apply to its roof guarantees, including maintenance and notification requirements. Actual coverage depends on the applicable guarantee and project documents.
Do not assume that a blister is automatically covered or excluded. Review the specific warranty terms before proceeding.
9. Keep a Blister Inspection Record
Whether a blister is repaired or monitored, maintain a clear record of its condition.
Record:
- The date of inspection
- The roof section and precise location
- Photographs showing the blister
- Approximate dimensions
- Whether the surface is intact or damaged
- Nearby seams, penetrations, and flashings
- Any evidence of moisture or leakage
- The recommended action
- The date of any follow-up inspection
Marking and photographing stable blisters makes it easier to determine whether they are growing, cracking, or remaining unchanged during subsequent inspections.
10. Choose the Right Corrective Action
The appropriate response depends on the findings of the roof evaluation.
- Monitor: For suitable, small, intact, stable blisters where the roof system remains sound.
- Repair: When the blister is damaged, weakened, or compromising the membrane or a nearby seam.
- Investigate further: When moisture, wet insulation, or a recurring defect is suspected.
- Assess the wider roof: When numerous blisters or repeated failures suggest a systemic problem.
Repair techniques vary by roofing system. The repair should follow the applicable manufacturer’s instructions and preserve the integrity of the surrounding roof assembly.
Bottom Line
Small blisters do not always require repair, but they should not automatically be ignored. Stable, intact blisters may be monitored when the roof system and surrounding materials are in satisfactory condition. Blisters that rupture, crack, expose reinforcement, weaken the membrane, separate seams, or indicate trapped moisture need closer evaluation and may require repair.
The safest approach is to document the condition, establish whether the blister is changing, and have a qualified commercial roofing professional determine whether monitoring, localized repair, or a broader roof assessment is appropriate. Avoid puncturing blisters or attempting repairs without considering the roof material and warranty requirements.
Related Questions
- What should you do when an underwriting inspection flags open seams or membrane damage?
- What should you do when an underwriting inspection flags ponding water?
- When is it better to replace a commercial roof rather than repair it?
Sources
- National Roofing Contractors Association guidance discussed in Professional Roofing: Back to the Start
- Roofing Contractors Association of British Columbia: Roof Maintenance Manual
- Johns Manville: Re-Roofing Guide
- Johns Manville: Peak Advantage Guarantee Information
Last reviewed: October 2026
Related Resources
How Often Should Commercial Roofs Be Inspected in Florida?
Need Commercial Roofing Help?
ShieldLine Roofing can help commercial property owners evaluate roof blisters, identify potential membrane deterioration, document roof conditions, and determine whether monitoring, repair, or a broader roof assessment is appropriate.
Disclaimer: This information is provided for general educational purposes and is not insurance, legal, engineering, or roofing warranty advice. Roofing conditions and repair requirements vary by roof system, manufacturer, property, and site conditions. Consult a qualified roofing professional and review applicable manufacturer requirements before undertaking repairs.
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