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Fire window

A fire window is a non-openable FRL-rated glazed unit (commonly -/60/-) that lets you put a window in a fire-rated wall. The window equivalent of a fire door.

By Chalkline. Last updated 25 May 2026. Verified 25 May 2026.

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A fire window is a non-openable, FRL-rated glazed unit (glass, frame, and seal as a tested assembly) that lets you put a window in a fire-rated wall. It is the window equivalent of a fire door: where a wall has to resist fire, an ordinary window would be a hole in that resistance, so a fire window provides a tested opening that holds the rating.

The rating. Fire windows are commonly specified to an FRL of -/60/-. Reading the three parts of that notation:

  • Structural adequacy (the first ”-”): not required, the window is not loadbearing.
  • Integrity (60): 60 minutes of resistance to the passage of flame and hot gases.
  • Insulation (the last ”-”): no insulation criterion, so radiant heat still passes through the glass. A fire window stops flame, not heat.

Where it is used. A fire window goes in an opening in a fire-rated wall, the situations the NCC Housing Provisions Part 9.2 sets for Class 1 residential work, principally an external wall less than 900 mm from the allotment boundary (not a road boundary), and separating walls between attached dwellings. In those walls, openings have to be protected; the fire window is the glazed option (the solid-core self-closing fire door is the doorway option) under the Part 9.2.3 opening-protection rules (verified 2026-05-25, ABCB Housing Provisions Part 9.2).

It is a specialist product. A fire window is a tested fire-rated assembly, not a standard window and not a substitute you can fake with toughened or even laminated glass in a normal frame. The whole unit (glass, frame, glazing method, seals) is tested together to achieve the FRL.

For a builder:

  • If a window is wanted in a fire-rated wall, it must be a fire window, or there is no opening. You cannot put an ordinary window within 900 mm of the boundary in a fire-rated wall.
  • Specify the tested assembly and FRL, and order early; these are specialist, longer-lead items.
  • Remember it does not insulate. -/60/- stops flame, not radiant heat, so it is about fire spread, not comfort.

Also known as: fire-rated window, FRL window.

See also

Last updated: 2026-05-25. Verified: 2026-05-25. Quarterly review for currency.

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