What Causes Bubbles or Blisters on a Flat Roof?
BERKELEY FLAT ROOF BLOG
What Causes Bubbles or Blisters on a Flat Roof?
Usually trapped moisture or air between roofing layers, expanding under heat. Not always an active leak, but worth checking.
Blisters form when moisture or air gets trapped between roofing layers during installation, or when water finds its way in through a small defect and gets trapped under the membrane. Sun exposure heats that trapped moisture, which expands and pushes the surface up into a bubble.
A small blister isn’t automatically an emergency, but it is a weak point — the membrane there is under more stress than the surrounding area and can eventually crack or split. Worth having checked, especially if you notice new ones forming or existing ones growing.
Noticing blisters on your flat roof?