Blistering and alligatoring are two common roof problems which result in your flat roof bubbling. Blistering is a problem that results in small bubbles forming underneath the flat roof surface. These bubbles often lead to cracks that can affect the overall integrity of the flat roof itself. Alligatoring is a related problem which occurs when the membrane of the flat roof develops cracks and begins to peel, much like an alligators skin.
Let’s look at the causes of flat roof bubbling and cracking and how they can be fixed.
Causes of Flat Roof Blistering
Blisters can form on your flat roof’s membrane for a number of reasons. Blisters on the membrane can result from leaks or even just the sun’s heat. Whatever the cause, these unsightly and potentially hazardous blisters are a serious problem as it can also shorten the lifespan of your roof.

It’s no surprise that the membrane has a hard time staying sealed if there is moisture between it and the roof deck. This can happen for a number of reasons: leaks, freeze/thaw cycles, or improper ventilation for instance. The result is a wind-blown look with ups and downs in the surface and blisters that resemble flat roof bubbling beneath the surface.
How To Fix Flat Roof Blistering
If your flat roof blisters show signs of serious damage, then it’s best to leave them alone. However, there are certain circumstances in which you should repair the blister:
- A cracked membrane
- The surfacing on the blistered area is coming off.
- The blister is causing the seam to open up.
- The blister is evident in an area that has high foot traffic
To repair a flat roof blister we recommend hiring a flat roofing specialist in your local area to help determine which material is best for you. Here’s another post we’ve written on which flat roofing system is best and how much does it cost to replace a flat roof.
Causes of Flat Roof Alligatoring
Alligatoring is a sign that your roof is ageing. As the sun’s UV rays dry and damage the flat roof’s surface, new cracks will appear and existing ones will widen if left un-repaired. Once alligatoring has begun, the structure may become prone to further damage which will eventually cause problems like ruined walls and ceilings, wood rot, mildew and mould, which can cause costly structural repairs.
How To Fix Flat Roof Alligatoring
To fix a flat roof that shows signs of alligatoring, you’ll need to clean your roof so that dust and loose particles are removed. Once this has been done, you can see the extent of the damage and make a decision as to what material is best for your property. Also, it’s key to make sure you inspect at least two times per year for new coatings and repair any blisters that could cause a leak. If the problem persists then we recommend replacing your flat roof entirely.
Is Your Flat Roof Bubbling or Cracking?
If you are facing any of the issues mentioned above, it is important that you take immediate action as it can only exponentially grow into a bigger problem if left unattended. Do ensure you look for early signs and that they are dealt with utmost care.
Here at SPS Roofing Ltd, we have a wealth of experience in undertaking flat roofing services in Devon and throughout South West England. Our team will be able to repair any type of flat roof bubbling and cracking, and if the problem is beyond repair, help install a brand new flat roof. Do get in touch with our team and we will provide a no obligation consultancy and a free quotation if required.