Water Blisters Under Roof Membrane

Blisters range in size from a penny to entire roof deck areas and can contain significant quantities of water.

Water blisters under roof membrane.

A roof blister is a raised area where there is a loss of adhesion of the roof. 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. Roof blisters are not limited to one type of roof system. Water leakage into the interior has resulted when the blisters expand to a crack or joint in the concrete slab.

What is a roof blister. They appear in all types of roofing systems residential and commercial. The most common cause of roof bubbling is poor installation of the roof. As the sun heats the roof those pockets expand and stretch the membrane.

If the membrane is not weathered or cracked repairs are typically not required. Roof bubbling is just what it sounds like spots where the rubber has lifted off the surface of the roof and formed a bubble or blister. The consequences of backwater laps are leaks and blisters which can lead to roof failure care explains. When the rubber membrane is bonded too quickly and prior to the adhesive drying bubbles will appear under the membrane caused by the trapped vapour from the adhesive.

In the most severe cases the membrane may need to be peeled back and re bonded. Bonding of the membrane to the substrate is of concern at perimeter areas particularly at low profile edges to eliminate probability of roof blow offs. In several cases the blisters were so large that replacement of the membrane was required. However water filled blisters under these membranes have been discovered on numerous buildings in the pacific northwest in recent years.

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. These bubbles of trapped air moisture can be caused by a variety of issues which are all avoidable if the roof design is correct and the membrane is correctly installed. In severe cases the membrane will crack when the pressure becomes too great. Whilst bubbles or blisters on a one piece epdm roof can be unsightly they will not cause the rubber membrane to fail.

As blisters extend over cracks or joints in the concrete water can leak to the interior. This area can fill up with air or water to form a blister which looks like a. The rv manufacturer simply didn t apply the adhesive evenly or left some dirt on the roof that the adhesive couldn t stick to. In time the bubbles will decrease as the membrane is partly breathable.

Blisters on adhered single ply membrane systems are typically caused by lack of adhesion at the point of application. Inadequate head laps and backwater laps are another mod bit installation problem that can allow moisture infiltration.