Popped nails in substrate under a liquid-applied roofing membrane

Causes

Substrate movement such as expansion/contraction 

Substrate deterioration

Substrate was nailed to the framing, not screwed

Listed under: membranes, Roof, cladding, framing, moisture, fixings and hardware, fixings, roof cladding, leaks, weathertightness

Cause

Substrate movement such as expansion/contraction 

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 it appears more serious, or the problem is getting worse and there is a risk that the roof may leak, the membrane may need to be removed and the substrate nail fixings punched in or replaced with countersunk screws. (Countersunk screws are typically required by membrane manufacturers.) If a new substrate is required it should be appropriate for the purpose, such as H3.2 CCA-treated, minimum 17 mm thick plywood. Ensure the recommendations and requirements of the membrane manufacturer are followed
  • if the membrane has not been in place for a minimum 15 years and requires replacement, a building consent will be required for the work
  • 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
  • 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

Back to top

Cause

Substrate deterioration

Repair

  • as for the first repair above. The membrane may need to be removed and the substrate repaired or replaced

Back to top

Cause

Substrate was nailed to the framing, not screwed

Repair

  • as for the first repair above. Nails are not appropriate for fixing of substrates under roof membranes – countersunk screws are typically required by membrane manufacturers. Refer to manufacturer requirements and to Building Code Acceptable Solution E2/AS1 clause 8.5.5.1 for guidance installing plywood substrates

Back to top