Toughened (tempered) glass for residential builds: AS 1288, AS/NZS 2208, applications

TL;DR

Toughened (also called tempered) glass is annealed float glass that’s been heated to ~620°C then rapidly cooled, putting the surface in compression and the core in tension. The result is 4 to 6 times stronger than ordinary annealed glass and, when broken, fragments into small cubic pieces rather than long sharp shards. That break pattern makes it a Grade A safety glass under AS/NZS 2208:1996 and the volume choice for any glazing in human-impact zones. Toughened glass is mandatory in residential applications under AS 1288:2021 for: shower screens (any glazed enclosure), balustrades, doors and side panels (glazing in or near doorways), low-level windows (sill less than 500 mm above floor), and bath enclosures. Toughened glass cannot be cut, drilled, or notched after the toughening process: every cut, hole, and edge profile must be specified before the glass goes into the toughening oven. The Australian Standards-compliant glaziers (licensed in NSW, registered in VIC) supply pre-cut, pre-toughened panels to the project’s exact specification. Common thicknesses in residential use: 6 mm (shower screens, basic interior), 8 mm (shower screens premium, side panels), 10 mm (frameless balustrades, structural glass), 12 mm (heavy frameless balustrades, large free-standing panels). The two specification calls: thickness (driven by panel size and structural design) and edge work (polished, bevelled, rounded, all must be specified before toughening) (verified 2026-05-13).

What it is

Float glass is made by floating molten glass on liquid tin, producing flat sheets of optically clear glass with a smooth surface and consistent thickness. Float glass in its raw form is annealed: slowly cooled, internally stress-free, and weak in flex. When it breaks, it breaks into long sharp shards.

Toughened glass takes the annealed float and applies a thermal cycle to put it under controlled internal stress:

Heat the glass to approximately 620 to 680°C in a horizontal toughening oven
Rapidly cool the surfaces with high-pressure air jets while the core is still hot
The surfaces solidify and contract more slowly than the core; the surfaces end up in compression, the core in tension

The result: the glass surface resists impact and surface stress 4 to 6 times better than annealed glass of the same thickness. The break pattern changes from sharp shards to small cubic fragments (typical 8 to 25 mm pieces) because the internal stress balance shatters the whole pane at once when a crack initiates.

The Australian standard for design and selection is AS 1288:2021; the materials standard for safety glazing is AS/NZS 2208:1996.

Grade A safety glass

AS/NZS 2208:1996 classifies safety glazing materials by their break pattern under impact test:

Grade	What it means	Where used
Grade A	Breaks into small fragments (safety glass)	All human-impact zones; the default residential safety grade
Grade B	Breaks but retains shape (laminated glass under impact)	Where retention matters more than fragment size

Toughened glass that passes AS/NZS 2208 tests is Grade A safety glass. Glass certified to AS/NZS 2208 carries the standard mark (typically a small “AS/NZS 2208” stamp etched at one corner of each pane). Unmarked glass cannot be used as safety glazing.

Where AS 1288 requires toughened glass

Under AS 1288:2021 and NCC 2022 Volume Two clause H4 (Safe movement and access), human-impact zones in residential buildings require safety glass (typically toughened or laminated):

Application	Toughened-glass requirement
Shower screen (any glazed enclosure)	Mandatory; typically 6 to 10 mm toughened
Bath enclosure (where bath is glazed)	Mandatory; typically 6 to 10 mm
Balustrade (deck, balcony, stair)	Mandatory; 10 to 12 mm toughened or laminated
Glazed door (entry door, internal sliding door, French door)	Mandatory if Class 1 or 2 (sill height factor); typically 6 to 10 mm
Window with sill less than 500 mm above floor	Mandatory if any pane area >0.85 m2 and within 800 mm of door
Side panels adjacent to doors	Mandatory if within 300 mm of the door
Glazing in a wet area	Mandatory in shower / bath enclosure
Roofing or skylight	Toughened OR laminated; engineer-specified

AS 1288:2021 Section 5 sets the detailed zones and thickness selection rules. The glazier reads AS 1288 against the building plan to select pane size, thickness, and grade for each glazed opening.

Critical rule: cannot be cut after toughening

Toughened glass cannot be cut, drilled, or notched after the toughening process. Any attempt to do so causes the entire pane to shatter into safety fragments. The stored internal stress releases at any crack.

This drives the supply chain:

The architect or designer specifies the openings (size, profile, edge work, holes for fixings)
The glazier takes off measurements and produces a cut list
The cut list goes to the toughening plant
Each piece is cut from annealed stock, edge-worked, drilled / notched as required
Each piece goes through the toughening oven
Each finished piece is delivered to site ready to install

Lead time for residential glass orders is typically 2 to 4 weeks from the cut list being placed. Rush jobs (“we need it tomorrow”) cannot be toughened in that timeframe; the field measurement and toughening cycle is the gating constraint.

The on-site implication: measurements must be dead accurate before the order goes in. If a pane comes back 2 mm too tall, it cannot be trimmed; the whole pane is remade.

Common thicknesses and applications

Thickness	Typical residential application
4 mm toughened	Mirror substrate, small frame inserts; rarely used as primary glazing
5 mm toughened	Light internal partition, picture-frame glazing
6 mm toughened	Standard shower screen, residential entry doors, side panels
8 mm toughened	Premium shower screens, large door panels, hinged shower doors
10 mm toughened	Frameless balustrades (typical), structural pool surround glass, large free-standing panels
12 mm toughened	Heavy frameless balustrades, large free-spanning panels, pool fencing
15-19 mm toughened	Engineered structural glass elements; specialist applications

The thickness is driven by:

Panel size (larger panels need thicker glass to resist flex deflection)
Loading condition (balustrade vs cladding vs shower screen)
Free-standing vs framed (frameless free-standing balustrades need thicker glass than framed)
AS 1288 structural design: the glazier or designer reads the AS 1288 selection table to confirm thickness

Edge work

Edge profiles on toughened glass must be specified before toughening:

Edge type	Description
Polished (flat polished, mitred edge)	Smooth glossy edge, the volume residential standard
Bevelled	Angled chamfer at the edge for decorative effect
Rounded (eased / arrissed)	Slight rounding to remove sharp corners; impact-friendly
Pencil polished	Rounded edge with high polish; premium
Sanded / matte	Translucent matte edge; specialist decorative

Edge work is part of the toughening cycle; you cannot polish a toughened edge in the field.

Bushfire (BAL) ratings

Under AS 3959:2018, glazing on bushfire-prone sites must meet the BAL rating of the property. The minimum requirements typically:

BAL rating	Glazing requirement
BAL-12.5	Standard toughened glass (4 mm minimum); window frames must also be BAL-12.5-rated
BAL-19	Toughened glass minimum 5 mm; AS 3959-compliant frames
BAL-29	Toughened glass minimum 6 mm; bushfire shutters or screens for some openings
BAL-40	6 mm toughened plus laminated outer pane; bushfire screens required
BAL-FZ (Flame Zone)	Specialist fire-rated glazing system (typically wired or specialty laminate)

The BAL rating drives the entire window assembly, not just the glass. The frame, the seals, and the install detail all matter.

Common defects and on-site issues

Pane comes back the wrong size: cannot be trimmed; rorder. Always confirm field measurement before sending to toughening oven.
Edge chip or scallop: a small chip at the edge of toughened glass can propagate and shatter the whole pane within hours or days. Reject any pane with visible edge damage on receipt.
Hole drilled at wrong location: rordering required. Holes must be specified before toughening.
No AS/NZS 2208 stamp on glass: glass cannot be used as safety glazing. Reject and order Grade A certified replacement.
Pane installed without setting blocks: setting blocks at the base of the pane in a frame distribute load; without them, the pane sits on the frame edge and stresses concentrate. Spontaneous shattering can result.
Spontaneous shattering (a real phenomenon in toughened glass): rare nickel sulphide inclusions in the glass cause cumulative stress; the pane can shatter weeks or years after install. Heat-soak treatment (HST) is an option for high-risk applications; the glass is heated to 290°C for several hours to trigger any latent shattering before it leaves the factory. Specifier-led for high-rise and high-risk residential.
Adhesive incompatibility: some structural adhesives (silicone, MS polymer) bond well to toughened glass; others react. Specify the adhesive system per the glazier’s recommendation.
Wrong glass for application: 6 mm toughened in a balustrade where 10 mm is required. AS 1288 selection check before order.

Cost (2026 indicative, ex-GST, supply only, single pane)

Item	Indicative cost
6 mm toughened, 600 × 900 mm shower screen panel	$80-150
6 mm toughened, 800 × 2100 mm door panel	$160-260
10 mm toughened, 1200 × 1100 mm balustrade panel	$200-380
10 mm toughened, 1200 × 1100 mm panel with polished edges + 4 holes	$280-440
12 mm toughened, 1500 × 1100 mm pool fencing panel	$300-540
Heat-soak treatment surcharge	+$80-160 per panel
Mitred edge premium	+$30-80 per metre of edge

Installed cost adds glazier labour (typically $150-300 per glazed opening for standard residential).

Standards and references

Standards Australia, AS 1288:2021 Glass in buildings: selection and installation. https://store.standards.org.au (verified 2026-05-13).
Standards Australia, AS/NZS 2208:1996 Safety glazing materials in buildings. https://store.standards.org.au (verified 2026-05-13).
Standards Australia, AS 3959:2018 Construction of buildings in bushfire-prone areas. https://store.standards.org.au/product/as-3959-2018 (verified 2026-05-13).
Australian Building Codes Board, NCC 2022 Volume Two Part H4 (Safe movement and access). https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two (verified 2026-05-13).