Water Blisters Under Roof 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.

Water blisters under roof membrane.

In severe cases the membrane will crack when the pressure becomes too great. 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. What is a roof blister.

As blisters extend over cracks or joints in the concrete water can leak to the interior. As the sun heats the roof those pockets expand and stretch the membrane. The most common cause of roof bubbling is poor installation of the roof. 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.

The roofer did not completely cover every square inch of the roof deck with adhesive as he re roofed. In several cases the blisters were so large that replacement of the membrane was required. The rv manufacturer simply didn t apply the adhesive evenly or left some dirt on the roof that the adhesive couldn t stick to. Blisters range in size from a penny to entire roof deck areas and can contain significant quantities of water.

In the most severe cases the membrane may need to be peeled back and re bonded. Whilst bubbles or blisters on a one piece epdm roof can be unsightly they will not cause the rubber membrane to fail. Blisters are the most common roofing problem. 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.

Flat roof blisterts bubbles occur as the direct result of hot air that rises from the crawl space between the top floor ceiling and the roof deck of the home. Bubble like or long thin raised areas on the roof are called blisters. This area can fill up with air or water to form a blister which looks like a. A roof blister is a raised area where there is a loss of adhesion of the roof.

Water leakage into the interior has resulted when the blisters expand to a crack or joint in the concrete slab. They appear in all types of roofing systems residential and commercial. Blisters on adhered single ply membrane systems are typically caused by lack of adhesion at the point of application. In some cases large blisters 2 deep have displaced concrete pavers creating hazardous walking conditions.

In time the bubbles will decrease as the membrane is partly breathable. If the membrane is not weathered or cracked repairs are typically not required. There are four main reasons why blisters bubbles occur on your flat roof. Roof blisters are not limited to one type of roof system.

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.