Vents, weepholes and gaps

Learn about retrofitting vents, weepholes and other gaps

Poorly designed or maintained vents and other perforations are a weak point in the building’s envelope which may allow embers and surface fire to ignite internal cavities.

Guiding principles

When retrofitting, your main objective should be to prevent flames and embers from entering your home 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.


  • 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 seal or fill existing weepholes. Weepholes are used to drain water – blocking them may result in water damage to the house and the build up of mould.
  • Do not use plastic or rubber clips or beadings 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’.