The design of the balustrade, including any decorative panels, must be such that any opening does not allow a 125mm "sphere" to pass through. At the stars, the space is tested above the nosing line (see Figure 3).
Where the fall height reaches more than 4m above the surface beneath (the height is measured from the floor to the ground in the fall zone), any horizontal elements within the balustrade between 150mm and 760mm above the finished floor level, must not facilitate climbing.
A wire balustrade must also meet these requirements. Post and wire spacing as well as the tension required to meet the 125mm sphere test and specified in Part 3.9.2 of BCA Volume 2, Housing Provisions.
A balustrade or other barrier must be designed to take loading forces in accordance with AS 1170.1 or AS/NZS 1170.1. This may require the services of a structural engineer.
Balustrade construction for Class 1 buildings BCA 2008 (Nat)
The Building Code of Australia (BCA) Volume 2 - Housing Provision contains requirements for balustrades and other barrier construction for Class 1 residential buildings. This information sheet contains the requirements in the 2008 BCA edition which incorporates some changes.
When a balustrade or other barriers are required:
A continuous balustrade or other barrier must be provided along the side of any roof to which public access is provided, any stairway or ramp, any floor, corridor, hallway, balcony, deck, verandah, mezzanine, access bridge or the like and along the side of any path of access to a building, if:
(a) it is not bounded by a wall; and
(b) it's level above the surface beneath, is more than -
(i) 4m where it is possible for a person to fall through an openable window; or
(ii) 1m in any other case (see Figure 1 below).
Balustrade height: (see Figure 2)
The height of a balustrade or other barrier must be as follows:
1m above the floor of any access path, balcony, landing or the like; or
865mm, measured vertically, above the no sings of stair treads or the floor of a ramp.
A transition zone is allowed where the balustrade height changes from 865mm on the stair flight or ramp to 1m at the landing. (see Figure 2).
865mm above the floor of a landing to a stair or ramp where the balustrade or other barrier is provided along the inside edge of the landing and is not more than 500mm long.