Fire windows



Timber Window Frame

  • The maximum wedging gap permitted under NZS4520 is 10mm on all 4 sides. Trim or pack the wall studs as appropriate. Do not adjust the window frame thickness.
  • Position window in opening, ensuring frame is square and true.
  • Fix Window Frame to Wall

Timber and Steel Stud walls

    • Wedge/pack gap between back of window frame and wall framing. Using 100 mm nails or 75 mm screws, Fix at 300 mm centres all 4 sides as close to centre of wall as possible to avoid glass.
    • Fixings can be alternated or on one side of the glass. T1 frames require the wedging gap to be wadded with Intumescent fire mastic sealant.
    • Prior to fitting architrave. Wall linings are to slot into T2 and T3 jamb rebates to seal the wedging gap.

Masonry walls

    • As per Timber frame instructions but substitute fixings with min. 9mm diameter x 100mm long masonry bolts. Stop the wedging gap between the window frame and masonry using cement grout. Fill the head with Intumescent fire mastic or wooden plug.


  • Window frame to timber stud - 10mm max.
  • Window frame to masonry wall - 10mm max.

Joining     (Additional instructions if multiple units are joined before installation)

With careful planning prior to manufacture, large window units can be supplied as separate items and joined together on site. This makes handling on site easier and can reduce heavy lifting for Health and Safety purposes.

  •  Align units back to back, ensuring that at least one of the units have the factory fitted intumescent seal. In the case of a fire the intumescent will expand and seal the gap between the two units. Joins should be glued with wood working PVA or construction adhesive and clamped prior to screwing together.
  • Connect the units with 10 gauge x 75mm Surefix screws at 100mm from each corner and at maximum 300mm centres between.
  • Fixings can be staggered either side of the glass if the glazing is centred in the jamb width.  An additional set of fixings are recommended for jambs over 200mm wide.
  • Once the unit is joined, follow the Window Unit fitting instructions above.