Fire windows

large icon 101

Fire windows 101

If you’re new to fire windows, this section will help you get started.  It explains the fire resistance rating system, the construction of our main window types and some terms people use when talking about windows.  To find out more, feel free to get in touch on (09) 579-8895.

Fire resistance ratings

The New Zealand system for fire resistance rating (FRR) is based on the British Standard.  It is very similar to the Australian Standard, but with some variations.  The various elements of a building, such as walls, floors, doors and windows are all rated using this system.

The rating is made up of these four measures.  The first three are measured in minutes.

  • Stability: This rating will always be zero for a  window (because they’re not load bearing) and is written as a dash.  Stability is how long an element can retain its load bearing capacity during a standard fire test that includes some extra load expected in a fire.
  • Integrity: How long an element will protect people and goods from flames and hot gasses.  This is typically determined by the materials’ flame erosion resistance, as well as the tightness of joints and their ability to limit smoke and gas penetration.
  • Insulation: How long it takes for the temperature of the non-fire side of the element to rise by the maximum permitted amount.
  • Smoke rating - This is not time related.  An element is either smoke rated or it is not. The letters Sm show when it is.  Through their service life the smoke seals are often overlooked as a maintenance item, yet their smoke control role in a fire is arguably the most significant element of life preservation in a fire.


A fire resistance rating lists the four measures in the order above.  If a window has an FRR of -/60/60 Sm it means the stability is nil, integrity 60 minutes, insulation 60 minutes and it is smoke rated.

fire window constructionNZ Fire Doors window Construction

Our windows are made of responsibly sourced materials that provide their tested and proven fire ratings, while ensuring they can provide the desired architectural aesthetics within your construction budget.  NZFD offer internal window units, i.e. room dividers or light wells in timber frames.

All fire windows are non-opening fixed pane in single or multiple panes in a range of combinations. All our fire windows are manufactured in our NZ factory using fire rated glass that we stock and cut to size ourselves.  Please contact the sales department to discuss unit and pane sizing and price options. 

Window talk

Here’s a brief explanation of some terms people use when talking about windows.  If there’s anything else you don’t understand, please get in touch. We’d be happy to explain.

Window: A standalone unit not connected to a doorset.  When attached to fire rated doors, they are defined as a sidelight or overlight.  Because windows have different regulations covering their dimensions and use as compared to sidelights and overlights, they are covered here in a separate section.

Trim size: Also known as the ‘hole in the wall’ this refers to the dimensions of the prepared opening for a  window. 

how to measure fire window trim

Installation tolerances: Allowed gaps, see installation details

Fire window: A complete unit made up of the glass, frame, and seals that are all appropriate to the window’s fire rating.