When your Bay Area roofing project involves determining whether or not to repair the blisters of a conventional low-slope membrane system, it is vital to first do a thorough analysis of the blisters themselves to decide if they are in fact in need of replacement. While it is generally preferable to leave the membrane undisturbed, in cases where the blisters have popped, it becomes necessary to have them either patched and reinforced or cut out and replaced altogether.

Results of a Popped Roof Blister

A popped blister will compromise the integrity of the roof’s membrane system by letting in moisture and causing potential leaks and infiltrating the insulation beneath the roof membrane and deck. Therefore, regular roof maintenance represents an important step you can take to help catch blisters before they pop by recognizing the characteristics of a potential problem before it becomes an expensive hazard. Blisters about to pop or otherwise damaged blisters are discernible by the looking at specific physical characteristics of the membrane and it’s surrounding areas and by paying attention to this criteria, you can make the most accurate assessment during this vital step of your Bay Area roofing project.

How to Detect Roofing Blisters

One characteristic often observed before blisters pop concerns the gravel atop the shingles or other roofing materials. Excessive loss of this gravel is one indication that blisters are expanding and thus in danger of popping so once you notice missing gravel from one or more of the roof’s shingles, it becomes necessary to inspect the membrane for further deterioration. Similarly, the membrane itself can also deteriorate once moisture has made its way into various layers of the roofing system during mishaps of the application or installation stage, such as voids created by poor adhesion.

Also pay close attention to the patterns of the blisters and the nature of their general composition. The frequency and size of the blisters also represent ways you can discern the extent of the damage and therefore, the extent of the necessary roof- repair or roof-replacing project.

Blisters in laps, for example which have reduced the lap coverage and exposed under laying seams and layers are problematic and should be consistently monitored for other signs of damage. Damage such as breaks and fatigue cracks located around the circumference of the shingles are indicative of blisters nearing the popping stage because it means that the moisture has evaporated and the resulting vapor is causing the membrane to expand.

Moreover, blisters that have formed in areas of high foot-traffic are even more susceptible to popping and exposing the roof to further damage because the smallest amount of pressure applied to blisters can result in the opening of those blisters.

Take into consideration that if you do decide to repair these blisters by using the traditional method of hot bitumen mopping, that contractors now agree that such a repair technique is only effective in eliminating a total of 60 percent of moisture from the felt material.


While deciding to repair or not to repair blisters or popped blisters is simply not a black and white decision, it is best to lean on the side of caution and make the repair because membrane damage which goes unnoticed could be hazardous to your roof and your home. If you have any further questions about whether to repair or not to repair, feel free to give your Bay Area Roofing Contractor, Yorkshire Roofing a call.