When Your Flat Roof Starts Bubbling: The Hidden Danger That Could Cost You Thousands

Flat roof membrane bubbling and blistering might look like minor cosmetic issues, but they’re actually early warning signs of potentially serious roofing problems. While roof blisters may not need immediate attention, if left unmonitored, they could lead to saturated insulation and a damaged membrane. Understanding what causes these bubbles to form—and knowing when to take action—can save property owners from costly repairs and extensive water damage down the road.

What Causes Flat Roof Membrane Bubbling and Blistering?

Roof systems with membranes are more prone to blistering because blisters are formed by gaps between the membrane plies or between the underlying substrate and the membrane. Blisters form when there are pockets of air or moisture trapped between layers of your roof’s membrane or between the membrane and the roof deck. Moisture and air can become trapped in voids between roofing plies or between the substrate and the membrane. As temperatures rise, the heat causes the water vapor to expand, which in turn causes roof blisters.

Several factors contribute to this problematic moisture entrapment:

• Poor Installation: In bituminous systems, voids can be created by improper adhesion during application, improper mopping viscosity, moisture in or on the felts, unfilled insulation joints, coverage of loose or trapped material particles, and distorted insulation or metal materials.
• Manufacturing Defects: Errors in the manufacturing process of roofing materials can create voids that result in blisters.
• Moisture Intrusion: The intrusion of moisture into the system — during application or in aged conditions — contributes to blister formation. Despite roofers’ convictions over the years that hot mopping eliminates moisture on felts or substrates in bituminous applications, studies have indicated that this theory is incorrect. It has been found that hot bitumen only eliminates up to 60 percent of moisture from the felt; the remaining 40 percent, which can be trapped in interply layers, can create blisters.

Identifying Different Types of Roof Blisters

On flat roofs, blisters appear as small bubble-like protrusions, thin and long raised lumps, or large, spongy areas. A roof blister is a raised area where there is a loss of adhesion of the roof. This area can fill up with air or water to form a blister – which looks like a bubble on your roof.

Not all blisters require immediate repair. To check a blister, lightly press on it with your foot. If the blister is hard and no air releases or water squirts out, you have a blister with vapor in it. The answer, in most cases, is nothing! Most blisters are a cosmetic issue. If the coating around a blister remains adhered to the substrate, blistering should not impact the performance of the roof.

However, certain types of blisters demand immediate attention from professionals specializing in flat roof repair nj services. While small blisters are generally harmless, ones of a significant size must be addressed to prevent further damage to your roofing system.

Professional Repair Techniques for Membrane Blisters

When blisters do require repair, professional contractors employ several proven techniques:

Complete Membrane Replacement Method

Membrane roof – Cut away the membrane that has lost adhesion, replace any wet insulation with like material, and replace the membrane with overlapping edges at least 6 inches wide. To repair a blister, cut away the membrane until you reach an area where the membrane still adheres to the roof tightly. You’ll then need to reapply new membrane material – at least as many layers as you removed – over the blistered area. Make sure that the new membrane extends at least six inches around the edges of the blister to ensure that your patch remains leak-proof despite the expansion and contraction caused by temperatures shifts.

X-Cut Method for Bitumen Roofs

On a bitumen roof, you may be able to cut an “X” into the blister and then peel back the loose membrane layers. Fill the void underneath the membrane with bitumen and then press the membrane back into place. Keep in mind that this particular repair method is only advisable if the membrane is otherwise undamaged.

Surface Preparation Requirements

To promote thorough adhesion of a patch, it is essential to begin by preparing the surface. Remove debris, contaminants, aggregate or loose surfacing from the surface of the membrane or flashing to be repaired. The area to be repaired should extend a minimum of 18 inches beyond the perimeter of the defect to provide an ample, clean area on which to install the patch and tie it into the existing roof membrane.

Prevention Strategies That Actually Work

The formation of blisters in all conventional low-slope membrane systems can be avoided with proper adhesion of the membrane to the substrate. One hundred percent adhesion is required during application. Property owners can take several proactive steps:

• Quality Installation: The key to preventing roof blisters from forming is to ensure that you apply dry materials like adhesives when the weather is dry as well. Make sure that the sealing substrates are dry after any weather event, then clean the area afterwards.
• Regular Inspections: According to GAF, a commercial roof should be inspected at least once a year. Annual inspections can help alert you to blisters and other roofing issues before they turn into major problems that require extensive repair.
• Professional Maintenance: Whether you have a new roof or your roof is a few years old, it’s important to have a maintenance contract with a local roofing contractor. A maintenance contract will ensure your roof is regularly inspected, and any damage will be addressed before it causes major damage to your substrate or facility.

When to Call Professional Contractors

If your blister needs to be repaired, it’s best to hire a contractor to perform the repair properly. If your roof is still under warranty, call the contractor that installed your roof to see what they can do to help you. While these steps may seem simple, it’s important to note that fixing flat roof blistering should be done by a professional roofing company. They have the expertise and tools to ensure proper repairs and prevent any further damage or issues. So, if you’re experiencing flat roof blistering, it’s best to rely on the expertise of a reliable roofing company.

For New Jersey property owners, choosing an experienced local contractor is essential. Our long-standing presence in the community, coupled with our commitment to quality and customer service, makes us the ideal choice for your roofing needs. A. Russo & Son Roofing, serving Monmouth and Bergen Counties since the 1980s, brings decades of experience to every flat roof repair project. We offer a 30-year labor warranty and a 20-year workmanship warranty, underlining our confidence in the quality of our work. We are also licensed and insured. Additionally, we offer same-day estimates and emergency services, demonstrating our commitment to customer service.

The Cost of Waiting

If left untreated, a blister can grow larger and allow more moisture to get in so that the problem gets worse until more extensive repairs and possible replacement is necessary…unless it pops! Flat roof leaks happen when bubbles, blisters, and cracks are not taken care of as soon as possible. The longer these are left untreated the more chances of damage and leaking can occur.

Professional contractors understand that flat roof membranes such as TPO, PVC, or EPDM require specialized installation and repair techniques, which is why it is important to work with a professional roofing company. While these types of roof membranes can last for many years, they require routine maintenance and inspections to identify and fix potential issues such as punctures, cracks, loose seams, shrinkage, chemical spills, UV degradation, abrasion, or other problems that could cause leaks.

Don’t let minor bubbling turn into major water damage. Early intervention by qualified professionals protects your investment and ensures your flat roof continues providing reliable protection for years to come.