Water Blisters Under Roof Membrane

Roof blisters are not limited to one type of roof system.

Water blisters under roof membrane.

As the sun heats the roof those pockets expand and stretch the membrane. What is a roof blister. 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. 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.

Water leakage into the interior has resulted when the blisters expand to a crack or joint in the concrete slab. 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. Blisters on adhered single ply membrane systems are typically caused by lack of adhesion at the point of application. They appear in all types of roofing systems residential and commercial.

There are four main reasons why blisters bubbles occur on your flat roof. In the most severe cases the membrane may need to be peeled back and re bonded. In severe cases the membrane will crack when the pressure becomes too great. Blisters are the most common roofing problem.

Vapour from contact bonding adhesive. In time the bubbles will decrease as the membrane is partly breathable. A roof blister is a raised area where there is a loss of adhesion of the roof. Bubbles can also be caused by water getting under the membrane which shouldn t happen with a good installation but may happen if any of the seams develop holes.

However water filled blisters under these membranes have been discovered on numerous buildings in the pacific northwest in recent years. The most common cause of roof bubbling is poor installation of the roof. In several cases the blisters were so large that replacement of the membrane was required. In some cases large blisters 2 deep have displaced concrete pavers creating hazardous walking conditions.

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. They occur when a gas usually water vapor is trapped within the roofing system either between the plies or between the plies and the insulation. This area can fill up with air or water to form a blister which looks like a. As blisters extend over cracks or joints in the concrete water can leak to the interior.

Whilst bubbles or blisters on a one piece epdm roof can be unsightly they will not cause the rubber membrane to fail. 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. The rv manufacturer simply didn t apply the adhesive evenly or left some dirt on the roof that the adhesive couldn t stick to. Bubble like or long thin raised areas on the roof are called blisters.

The roofer did not completely cover every square inch of the roof deck with adhesive as he re roofed.