Sheet membrane roofing – lifting of sheet joints

Cause

Loss of adhesion at the joint

Repair

  • problems with waterproof roofing membranes should be attended to without delay to avoid the risk of rainwater entering the building
  • if the membrane roof was installed within the last few years, call back the original installer to have a look at it. Roofs still under warranty should only be repaired/replaced by the contractor who carried out the original membrane application or by another applicator approved by the membrane supplier

  • application, repair or replacement of roofing membranes is restricted building work. Where done by a tradesperson, it must be carried out or supervised by a licensed building practitioner with the relevant licence

  • if the problems are severe enough that the whole membrane must be replaced, and it has not met minimum Building Code durability provisions applicable (likely to be 15 years), a building consent will be required

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

Cause

Substrate movement has caused damage to the membrane

Repair

  • as above but be aware that poor construction/installation of the substrate will need to be addressed first. It may be that the substrate needs to be repaired/replaced before the membrane can be replaced

Cause

Water has got under the membrane causing a breakdown of the adhesive

Repair

  • as for the first repair above. If the problem may have existed for a long time and resulted in a significant amount of rainwater entering the building, ask a registered building surveyor to assess the roof for potential damage

Cause

The joint is within an area where water ponds 

Repair

  • as for the first repair above, but the issue of ponding will also need to be addressed if water is sitting for long periods

  • ensure there are no blockages to drainage outlets

  • if the outlets are too small, increase in size or add an additional outlet

  • where there is insufficient fall to outlets, the roof framing/substrate may need to be rebuilt with additional fall

Cause

Adhesive failure at joints

Repair

  • as for the first repair above. This is a common issue if there is ponding at a joint, so the issue of ponding will also need to be addressed