Vents, weepholes and gaps

Embers and surface fire can penetrate the building through poorly managed vents and perforations

Vents and weepholes are a necessary part of a buildings design, providing clean air and helping to regulate moisture and airflow. Although necessary, poorly designed and maintained perforations are a weakness in the building’s envelope, which may allow embers and surface fire to ignite internal cavities.

Guiding principles

When designing vents and other perforations, your main objective should be to prevent flames and embers from entering the home via the ventilation system, and to safeguard vents and weepholes from collapse, displacement, breach, and from burning and producing additional heat and toxic gases.

As a rule, ensure that all openings are made with tight-fitting non-combustible materials and that individual gaps are no larger than 2mm.

Close up of stainless metal mesh

Stainless steel mesh can protect vents in bushfire prone areas (source: Mrs_ya/Shutterstock)


  • Vents, mesh and frames should be made of stainless steel or bronze. Aluminium is the next best option.
  • Seal all gaps that are wider than 2mm.
  • Keep the areas around vents and weepholes clear of vegetation and other objects that might burn or block the ventilation system.


  • Avoid plastic-coated glass fibre screening materials.
  • Do not remove (or build over) an existing vent before considering whether this will hamper the flow of ventilation. This includes air conditioners and heaters.
  • Do not use plastic or rubber beadings or clips to secure vents and screens.
  • Do not use slotted vents or vents with gaps that are wider than 2mm.
  • Avoid tested vent systems that use the ‘probe criteria’.