Expanding or Trapped Air within The Roof Structure

Why are there bubbles or blisters on my EPDM rubber roof?

Though unsightly and nerve-racking, bubbles or blisters on an EPDM roof will not cause the rubber membrane to fail and your EPDM rubber flat roof will remain watertight.

However, the bubbles of trapped air and moisture can be avoided if the membrane is correctly installed. Therefore, it may be cost-effective in the long run to contact a roofing contractor to install the rubber roof.

There are two main reasons why there would be blisters or bubbles on your EPDM rubber flat roof:

The first cause is vapour from the bonding adhesive
  • During installation, the Quickbond Contact Bonding Adhesive is used to attach the EPDM membrane to upstands and the perimeter of the roof deck. The solvent-based adhesive must be used in a well-ventilated area and applied to both mating surfaces. The installer must wait for the adhesive to dry (tack off) before adhering the rubber to the substrate. Therefore, if the adhesive does not tack off and the rubber is bonded prior to the adhesive drying then bubbles will appear.
  • As EPDM rubber is very breathable, the bubbles are in most cases not severe and will disappear over time. In severe cases, the membrane may need to be peeled back and re-bonded.
The second cause is expanding trapped air within the roof structure
  • Bubbling can occur on warm deck roof designs where the EPDM is fully bonded onto either a timber deck or insulation.
  • Boards fitted with large gaps and damp under the insulation result in trapped moist air. This causes expanding trapped air as the membrane will expand when the sun warms the roof and contract in the evening.
  • It is vital to ensure that all insulation boards are fitted snug together and the roof structure is dry underneath.
  • Any gaps can be filled with an expanding foam adhesive to stop the trapped air lifting the membrane.

If you have any queries, please get in touch with our friendly team. Call us on 01392 927729 or email sales@rubberflatroof.co.uk.