Window restrictor
A window restrictor limits openable windows to 125 mm where a 2 m+ fall exists in Class 1 and Class 2 buildings. AS 5203 types and the two-step release rule.
Ask Chalkline about this →A window restrictor is a device that limits how far a window can open. Under NCC 2022 ABCB Housing Provisions Part 11.5, a restrictor is mandatory on any openable window in a Class 1 (house) or Class 2 (apartment) building where the opening exceeds 125 mm and the sill is 2 m or more above the surface below (NCC 2022 HP Part 11.5, verified 2026-05-13). The device must comply with AS 5203:2016.
The 125 mm rule
The rule is triggered when both conditions exist: the window can open wider than 125 mm, and the fall from sill to surface below is 2 m or more. If either condition is absent no restrictor is needed.
Two-step release
A restrictor can include a release so adults open the window fully for cleaning or egress. Any release must require two separate, sequential actions to override the restriction. A single-push button or single flip-up latch does not comply.
Device types
| Type | How it works |
|---|---|
| Cable restrictor | Cable limits sash travel; key or two-finger pinch releases in two steps |
| Scissor restrictor | Linked-arm device; two-step lever release |
| Screen restrictor | Structural screen tested to AS 5203; physically limits the opening |
A standard fly screen is NOT a window restrictor. It blocks insects, not the opening. Only a screen specifically tested to AS 5203 qualifies.
For a builder
Missing restrictors on upper-storey windows are a common practical completion defect. Fit them before handover; post-frame retrofits cost more and take longer.
Also known as: window opening restrictor, child window restrictor, openable window restrictor.
Category: Windows and doors / child safety.
Related
See also
References
- Standards Australia, AS 5203:2016 Protection of openable windows in buildings. https://store.standards.org.au (verified 2026-06-11).
- ABCB, NCC 2022 Housing Provisions Part 11.5. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions (verified 2026-05-13).
Last updated: 2026-06-11. Verified: 2026-06-11. Quarterly review for NCC currency.