Bubbles in sheet membrane roofing

Cause

Poor adhesion of the membrane to the substrate

Repair

  • where the problem is extremely minor with no risk of leaks, watching to see whether it gets worse may be an appropriate first response. Where significant areas are not properly adhered, the membrane should be removed and replaced with a material compatible with the substrate

  • if the membrane was installed in recent years, call the installer back. Roofs still under warranty should be repaired by the contractor who carried out the original membrane application or by another applicator approved by the membrane supplier

  • installation and/or repair of membrane roofs is typically not a DIY job. Membrane manufacturers and suppliers typically train and license applicators in the use of their membranes. A warranty may only apply where application or repair is carried out by someone licensed by the supplier

  • work on roofs is restricted building work under the Building Act and anyone engaged to carry out this work must be a licensed building practitioner or be supervised by an LBP

  • • check the condition of membrane roofs at least once a year to ensure there is no debris on the roof, no damage and no breakdown of the membrane surface

Cause

Adhesive misses – the membrane is not fully adhered to the substrate

Repair

  • as above

Cause

Moisture from a damp substrate or roof framing is being drawn to and trapped by the membrane

Repair

  • as for the first repair. Provide or increase the ventilation to remove moisture from the roof space, but be aware that existing bubbles may not disappear after this

Cause

The framing and/or substrate moisture content was too high when the membrane was installed

Repair

  • as for the first repair. Provide or increase the ventilation to remove moisture from the roof space, but be aware that existing bubbles may not disappear after this

Cause

Moisture in living spaces below is getting into the roof space (typically via open downlights) and being drawn through the substrate where it is trapped by and accumulates under the membrane 

Repair

  • as for the first repair. Provide or increase the ventilation to remove moisture from the roof space, but be aware that existing bubbles may not disappear after this. Reduce moisture in living spaces and replace the older-style downlights either with ceiling mounted downlights or new recessed downlights with a better seal to prevent air movement

Cause

Subsequent coats of liquid-applied membrane are applied before preceding coats have cured

Repair

  • as for the first repair