Australian Standard, AS 1288, Glass in buildings —Selection and installation, sets out procedures for the selection and installation of glass in buildings, subject to wind loading, human impact, and special applications such as overhead glazing, balustrades and glass assemblies.

The various requirements given in AS1288 include requirements for glazing, which include the following:

(a) Clause 8.1 states that this Section sets out basic installation requirements for glass.

Note 1 to this section states: “This section does not preclude the use of other methods or systems for glazing, provided the alternate method or system can be demonstrated to satisfy the requirements for correctly supporting the glass within the frame, or glazing system.”

Note 2 to this section states: “Patent and other proprietary systems are not described in this Section.”

(b) Clause 8.4 gives requirements for glazing materials as follows.

i. A glazing material shall be used only for the purposes recommended by the manufacturer.

ii. A glazing material shall be used only where compatible with contiguous materials, including the rebate surface finish, setting or location blocks, distance pieces and glass type.

iii. The application of glazing materials shall be in accordance with manufacturers’ instructions.

iv. A glazing material shall only be used where its life expectancy (durability) has been established. NOTE: The manufacturers’ advice should be sought for information regarding life expectancy.

(c) Clause 8.6 gives requirements for location blocks as follows.

(i) The number and position of location blocks shall be as shown in Figure 8.3 and Figure 8.4.

(ii) Location blocks shall be—

(a) a minimum of 25 mm long;(b) at least as wide as the glass thickness;

(c) positively located to prevent displacement in service; and

(d) sufficiently resilient to accommodate movement within the frame, without imposing stress on the glass, and of resilient, non-absorbent material.

NOTES:

1 Location blocks are used between the edges of the glass and the frame to prevent movement of the glass within the frame by thermal expansion or when the window or door is opened or closed. They are required to prevent the weight of the glass from causing the frame to become out of square.

2 Extruded rubber material with 55–65 shore-A hardness is recommended.

In view of the above requirements and notes, I would recommend that some means be employed in the glazing of balustrades, such as location blocks used between the edges of the glass and the frame, to prevent movement of the glass within the frame by thermal expansion or other movements due to wind or building movements.

For this purpose, since the use of other methods or systems for glazing are not precluded, in our opinion, structural silicone sealant may be used as location blocks at the edges to prevent the movement. Please note that, if the glass is laminated, then the sealant also needs to be compatible with the inter-layer.

Written by Dr Ignatius Calderone

Director, Calderone and Associates Pty Ltd.