AS 1288 Glazing Selection and Installation for Residential Windows

What it is

AS 1288 Glass in buildings: Selection and installation is the Australian Standard that tells a builder which glass to put in which opening, how thick it needs to be for the design wind pressure, and where safety glazing is mandatory. The NCC calls up AS 1288 through Volume Two Part H1 (structural) and Part H4 (safety glazing), making compliance with the standard a deemed-to-satisfy pathway for Class 1 and Class 10 buildings. Designers, glaziers and builders all share liability for getting it right because the standard covers selection (the designer's call), supply (the glazier's call) and installation (the builder's call).

The 2021 edition is the version currently referenced by NCC 2022. It supersedes AS 1288-2006 and tightens several safety glazing requirements around bathrooms and pool surrounds.

Safety glazing zones

AS 1288 defines specific zones where Grade A safety glass is the only acceptable option. Grade A means the glass is tested to AS/NZS 2208 and either breaks into small blunt fragments (toughened) or holds together on a plastic interlayer (laminated). The mandatory zones in a Class 1 dwelling are:

• All glazing in doors and side panels within 300 mm of the door edge, full height
• Glazing within 500 mm of the floor in any wall (a window with a sill at 400 mm needs safety glass to at least 500 mm above floor level)
• All glazing in bathrooms, ensuites, laundries and shower screens regardless of height
• Glazing within 1200 mm of a pool, spa or sauna at any height
• Any pane larger than 1.2 m2 in a wall with a low sill

The 500 mm floor zone catches a lot of low sill windows in modern open-plan designs. A builder ordering 6 mm float for a 400 mm sill window is non-compliant, and the glazier should refuse the order.

What "Grade A safety glass" means in practice

Toughened glass is around four times stronger than annealed float of the same thickness and shatters into small cubes when it fails. It cannot be cut, drilled or notched after toughening. Laminated glass is two or more sheets of float bonded with a polyvinyl butyral (PVB) interlayer, and it holds together when broken, which makes it the right choice for overhead glazing, balustrades and any pane where staying in the frame after impact matters.

Heat-strengthened glass is not Grade A safety glass. It sits between annealed and toughened in strength, breaks into larger fragments, and is used in laminated build-ups to reduce the risk of spontaneous nickel sulphide inclusion failure. Specifying heat-strengthened where toughened is needed will fail inspection.

Thickness selection for wind load

AS 1288 Section 5 gives a chart-based and equation-based method for sizing glass against design wind pressure. The inputs are pane width, pane height, design wind pressure (from AS 4055 for housing or AS/NZS 1170.2 for engineered designs), glass type and aspect ratio.

A 1500 mm by 1500 mm fixed pane in a wind classification N3 site (around 1.5 kPa design pressure) needs 6 mm annealed float as a minimum. The same pane in a C2 cyclonic site needs 10.38 mm laminated, plus impact-resistant framing per AS 2047. The jump in thickness as wind classification rises is not linear, and builders in cyclonic regions should never substitute lighter glass without rerunning the calculation.

Installation requirements

The installation provisions in AS 1288 Section 3 cover edge clearances, setting blocks, sealants and frame deflection limits. Key rules a builder needs to know:

• Minimum edge clearance is 3 mm for most domestic glass, increasing to 5 mm for laminated panes over 1.2 m2
• Setting blocks at the quarter points of the bottom edge, made of EPDM or silicone, never timber
• Glazing rebate depth must exceed minimum cover by 3 mm to allow for thermal movement
• Frame deflection under design wind pressure must not exceed L/175 for single glazing or L/240 for double-glazed units, where L is the unsupported span

Frame deflection is where insulated glass units fail prematurely. A flimsy aluminium frame that deflects past L/175 will break the edge seal of a double-glazed unit within a few years, and the IGU will fog from the inside.

How it interacts with energy and acoustic specs

AS 1288 sets the structural and safety floor for glass selection. Energy performance comes from NCC Volume Two Part H6 and the NatHERS rating, which drives U-value and solar heat gain coefficient (SHGC) targets. Acoustic performance for sound separating walls comes from NCC Part F7 (covered separately). All three constraints stack: the glass must meet the safety zone, the wind load, the U-value and the Rw at once. The cheapest pane that meets all four is usually 6.38 mm laminated low-E in an argon-filled IGU with a 12 mm cavity, but the maths needs to be run on every project.

What goes wrong on site

The most common AS 1288 failures are wrong glass in low sill windows (annealed where Grade A is required), missing setting blocks (glass resting on the aluminium frame rebate), no edge clearance (glass cut to exact rebate size), and timber packers under the glass instead of EPDM setting blocks. Each of these will pass visual inspection but fail an AS 1288 audit, and they create long-tail warranty claims when the glass cracks under thermal movement six months later.