Updated May 2009

13.23 BALUSTRADE & FENCE DESIGN

A glass balustrade is a modern and stylish safety

barrier, which provides strength and safety in

conjunction with maximum unobstructed views.

Glass balustrades can be free-standing cantilever glass

without vertical support, or infill balustrades supported

by post, glass fins or other frame members, or

combinations of these systems.

Infill types are normally two or three side supported by

channels clamps or disc clamp fittings.

The NZ Building Code specifies performance

requirements and design principles for balustrades.

It is important that all the requirements are met and a

producer statement of compliance is provided.

It is not acceptable to install a balustrade purely on the

basis of an architectural design drawing, and the

installer must ensure it has been engineered and the

product is fit for purpose.

NZ Building Code Compliance

The following sets out compliance with NZBC

Acceptable Solutions.

F2 Hazardous Building Materials

F2/AS1 refers to NZS 4223:Part 3:1999 as a means of

compliance and requires Grade A Safety Glass to be

used. Infill panels are required to be not less than 6mm

thick and Table 3.8 is provided for glass requirements

to some balustrade types. However, recent changes to

B1/VM1 mean that these tables do not comply with

AS/NZS 1170, so now tables are provided in this

section.

Specific design is required for structural balustrades

and fences and design tables are provided in this

section based on the new AS/NZS 1170 whic h replaces

NZS 4203.

B1 Structure

The compliance document B1/VM1 was amended in June 2008 and

became effective in 1 December 2008.

It now cites AS/NZS 1170 .1 which details the design actions for barriers in

Table 3.3

This has changed the requirements for barrier loads, and has increased

the number of occupancy types, increased the magnitude of some top

edge and infill loads , and has introduced a concentrated load case.

In B1/VM1, paragraph 2.2.7 provides specific information on the height of

application of the loads.

Wind loads must also be considered and this is important in high rise or

high wind load situations as the wind load may dominate design over the

other loads

AS/NZS 1170 also provides recommendations for deflection limits in Table

C1 and these are more stringent than the normal allowable deflection

requirements for toughened glass balustrades, which are span/60 for infill

panels and height/30 or 30mm maximum for freestanding glass.

It is important to remember that when balustrades have no handrail, the

glass is required to support the handrail load and this can be very

restrictive on design.

In addition consideration must be given to the result of glass failure and

Metro GlassTech recommends interlinking handrails on structural

balustrades in case of glass failure.

Type of occupancy

for part of the

building or structure

Specific uses

A - Domestic and

residential activities

All areas within or serving exclusively one

dwelling including stairs, landings, etc. but

excluding external balconies and edges of

roofs (see C3)

Other residential, (see also C)

B,E - Offices and work

areas not included

elsewhere including

storage areas

Light access stairs and gangways not

more than 600 mm wide.

Fixed platforms, walkways, stairways and

ladders for access (see note)

Areas not susceptible to overcrowding in

office and institutional buildings also

industrial and storage buildings

C - Areas where people may congregate

C1/C2 – Areas with tables

or fixed seating

Areas with fixed seating adjacent to a

balustrade, restaurants, bars, etc.

C3 – Areas without

obstacles for moving

people and not

susceptible to over-

crowding

Stairs, landings, external, balconies,

edges of roofs, etc.

C5 – Areas susceptible to

over-crowding

Theatres, cinemas, grandstands,

discotheques, bars, auditoria, shopping

malls (see also D), assembly areas,

studios, etc.

D – Retail areas All retail areas including public areas of

banks/building societies (see C5 for areas

where overcrowding may occur)

F4 Safety from Falling

F4/AS1sets out barrier heights and construction

requirements for buildings including balconies,

swimming pools and opening windows.

Barriers or balustrades are required when people can

fall 1m or more from an opening in the external

envelope or floor of a building or from a sudden change

in level within or associated with a building

The minimum barrier heights are;

Detached dwellings and within household units of multi-

unit dwellings.

900mm on stairs and ramps and their landings

1000mm on balconies, and decks, and edges

of internal floors or mezzanine floors edges of

internal floors.

All other buildings and common areas of multi-unit

dwellings:

900mm on stairs and ramps

800mm for barriers within 530mm of the front

of fixed seating

1100mm in all other areas

1200mm for swimming and spa pools.

Note - Heights are measure vertically from the floor level

(ignoring coverings) on floors landings and ramps and from the

pitch line or stair nosing on stairways

Toe holds are defined as 15mm ledge over the height

of the barrier, and if greater than 15 mm a 60 degree

fillet angle to the horizontal is required.

Openings in barriers frequented by children under 6

should not be more than 100mm, and not allow a

100mm sphere to pass through.

The triangular opening formed by the stair riser and the

bottom of the balustrade shall allow a 150mm diameter

sphere to pass through.

D1 Access Routes

D1/AS1 sets out the requirements for handrails for access routes including

stairs, to or within buildings.

Handrails are required on all stairs and Accessible Routes (for people with

disabilities) if the slope exceeds 1 in 20 and they must comply with the

requirements of D1/AS1. The handrail must have features to cope with

people with disabilities in Accessible Routes and the handrail must be 32

to 50 mm diameter. This is less than many standard handrail designs.

B2 Durability

B2/AS1 deals with durability and minimum durability requirements for

materials and fixings used in balustrades and barriers. The requirements

range from 5,15 to 50 years depending on whether the element is

structural and how difficult it is to replace. In some cases the 50 year

requirement will apply to fixings for structural elements of safety barriers

E2 External Moisture

E2/AS1 deals with balustrade to wall and deck drainage junctions and

balustrade fixing to ensure the building is water tight, and covers

compatibility of materials

Fencing of Swimming Pools Act 1987 (FOSPA)

F4 and F4/AS1 still refer to the FOSPA, however a new standard NZS

8500:2006 S afety Barriers and Fences around Swimming Pools and Spas

and Hot Tubs is available.

Fencing requirements under this act apply to pools altered since 1991.

Refer to the FOSPA for the requirements, but as a guide the key

performance requirements are:

Pools having a depth of water exceeding 400mm shall have

barriers

Barriers shall restrict the access of children under 6 years

All gates and doors shall be fitted with latching devices not

readily operated by children and must automatically close from

150mm or more from the closed position

Gates must not open inwards to the pool area

Latches must be fitted which are only accessible by reaching

1.5 m above ground on the outside

Barriers shall have no permanent objects on the outside that can

provide a climbing step.

If the pools side walls exceed 1.2 m height or the maximum depth of water

is less than 400mm then fences are not required.

For balconies overlooking a pool area – refer to NZS 8500 .

Balustrade Design Types

Balustrade glass designs normally fall into the following

types;

Type SB1. Structural Balustrade – Cantilevered glass

Type SB2. Structural Balustrade – 2 Edge-Point fixed

Type SB3. Structural Balustrade – 2 Edge support

Type SB4. Structural Balustrade – 3 Edge support

Type IB1. Infill Balustrade – 4 Edge support

Type IB2. Infill Balustrade – 2 Edge support

Type IB3. Infill Balustrade – 2 Edge-Point fixed with

handrail in front of glass

Tables

GANZ have prepared a series of design charts for the

above types based on design loads from AS/NZS

1170.1 and B1/VM1. These are an alternative solution

for compliance with the NZBC

The tables show the maximum ULS wind pressure for

each thickness and if the wind loads for the glazing

location exceed these pressures specific design will be

required. This can occur in some high rise buildings –

or exposed sites.

For other design types specific design is required.

Handrails

Handrails are not always required, but they normally fall

into three categories

Load Supporting Handrail (handrail takes the

load). This infers that the handrail

mechanically fixed to the structure,

independent of the glass, but the glass can be

connected to it. These handrails must be

designed to support the barrier loads. This is

normal with an infill balustrade.

Non Load Supporting Handrail (Glass takes

the Load).

This infers that either the top edge of the glass

acts as the handrail or the glass supports a

handrail that is fixed to the glass and relies on

the glass for structurally support. The glass

must be designed to support the barrier loads.

Interlinking Handrail

This infers the handrail is non load supporting,

unless an panel breakage occurs, and is

connected to adjacent panels of glass, or the

building, where the adjacent panels are at

least 1000mm wide and three or more panels

of glass form the balustrade. If any one panel

fails the remaining panels and handrail shall

be capable of resisting the barrier

.

NOTE. Metro Glasstech recommends interlinking

handrails on all structural balustrades