Glass thickness affects strength, weight, acoustic performance, and cost. Choosing the right thickness for each application is both a compliance issue and a practical one — glass that's too thin is unsafe, and glass that's unnecessarily thick costs more and adds weight that hardware must be rated for. Here's a complete guide to thicknesses used in residential glazing and how to select the right one.

How Thickness Affects Performance

Glass strength increases non-linearly with thickness. Doubling the thickness more than doubles resistance to wind loading — a 12mm pane is roughly eight times stronger than a 6mm pane of the same size. This means that moving one step thicker is rarely expensive but can significantly increase your safety margin.

Weight, on the other hand, increases linearly: every 1mm of thickness adds exactly 2.5 kg/m² because glass density is consistently 2,500 kg/m³. For large panels, this difference is significant for both manual handling requirements and hardware specification. Use the Glazing Calculator to calculate the exact weight of any panel configuration — essential for specifying hinges, slides, and patch fittings correctly.

4mm Glass

The lightest common option at 10 kg/m². Appropriate for: • Internal picture frames and display cabinet glass • Small fixed panels in sheltered, low-wind locations • Secondary glazing inner panels where weight is a priority

Rarely appropriate for exterior applications due to insufficient wind load resistance. Its main appeal is weight and cost.

6mm Glass

The workhorse of residential glazing at 15 kg/m². Suitable for: • Standard windows and fixed panels up to moderate sizes • Sliding and hinged doors (when toughened) • Shower screens (when toughened — minimum requirement) • Human impact safety glass zones under AS 1288 (when toughened or laminated)

When toughened, 6mm meets Grade A safety glass requirements for most human impact locations. It's the default starting specification for most residential work.

8mm Glass

Used where 6mm doesn't meet wind loading requirements or where additional rigidity is needed, at 20 kg/m²: • Larger fixed panels where 6mm span tables are exceeded • Frameless and semi-frameless shower screens for a more premium feel and better rigidity • Internal glass partitions • Balustrade infill panels in framed systems

10mm Glass

Specified for large fixed panels, commercial shopfronts, and high-wind exposure locations at 25 kg/m²: • Fixed panels over 1.5m in either dimension in moderate wind areas • Frameless balustrade infill panels in many configurations • Commercial facade glazing

At 10mm toughened, a 1.5m × 2.4m panel weighs 90 kg — two people and suction cups are the minimum requirement. Confirm hardware ratings before specifying.

12mm Glass

The standard for structural applications at 30 kg/m²: • Frameless glass balustrades — the most common application • Large pivot and hinged doors • Structural glass fins and feature walls • Frameless pool fencing

A 1.0m × 2.1m panel in 12mm toughened weighs 63 kg. Mechanical lifting is required for safe installation. Always factor lifting equipment into the quote — it's a direct cost, not a contingency.

Double Glazed Unit (IGU) Configurations

For IGUs, the format is outer glass / spacer / inner glass. Common residential configurations: • 4/6/4 slim-line: 14mm total — used for tight rebates with insufficient depth for standard units • 4/12/4: 20mm total — budget double glazing, improving on 4/6/4 thermally • 6/12/6: 24mm total — standard residential, U-value approximately 2.7 W/m²K • 6/16/6 with low-E: 28mm total — good performance, U-value approximately 1.8 W/m²K • 6/16/6 with low-E and argon: 28mm total — high performance, U-value approximately 1.2–1.4 W/m²K

The minimum rebate depth for a 24mm IGU is typically 18–20mm. Many older frames have rebates of only 10–14mm — check depth before committing to IGU replacement. See Single vs Double Glazing for a detailed performance comparison.

Choosing the Right Thickness — The Decision Process

Follow this sequence for every panel:

Is this location a human impact zone under AS 1288? If yes, safety glass is mandatory regardless of panel size or wind loading. See Understanding AS 1288 for location-by-location guidance.

Does the panel size and wind region require a specific minimum thickness? Check the span tables in AS 1288 or consult your supplier's specification software.

What does the weight of the selected thickness mean for handling and hardware? Calculate using the Glazing Calculator and adjust hardware specifications accordingly.

Is there a simpler specification that meets all the above requirements at lower cost?

When in doubt, one step thicker is always a conservative choice and rarely adds much cost. Never specify thinner than the documented minimum for the application.

Frequently Asked Questions

How do I know which thickness meets wind loading for my location?

The most practical approach is to ask your glass supplier — they have specification software that takes wind region, building height, terrain category, and panel dimensions as inputs. You can also reference AS 1288 directly, which includes selection tables. For large or unusual panels in high-wind areas, a structural engineer's confirmation is worthwhile.

Is 6mm toughened strong enough for a frameless shower screen?

For standard shower screens up to 900mm wide and 2000mm tall, 6mm toughened is adequate and is the most common specification. For frameless screens over 1.0m wide, pivot-hinged screens, or screens with minimal frame support, 8mm or 10mm toughened provides better rigidity and a more substantial feel. Many customers upgrading a bathroom prefer 10mm for its premium appearance.

Why is 12mm glass so much more expensive than 10mm?

12mm glass is manufactured in lower volumes and requires different parameters in both float and toughening processes. The cost per m² for 12mm toughened is typically 30–50% more than 10mm toughened — a significant jump. Budget accordingly when specifying frameless balustrades.

Can different thicknesses be combined in one double-glazed unit?

Yes, and for acoustic performance it's often recommended. Using different thicknesses — such as 6/12/10 — prevents acoustic resonance between the panes at the same frequency, which significantly improves sound reduction compared to matched thicknesses like 6/12/6. For noise-sensitive applications, specify asymmetric glazing.

What is the maximum panel size for 6mm toughened glass?

Maximum size depends on wind region and building height — there's no single universal answer. In low-wind areas at ground level, 6mm toughened can span reasonably large panels. In wind region C or D, maximum spans are considerably smaller. Always verify against span tables rather than using rules of thumb.

Common Glass Thicknesses for Residential Windows