Structural Silicone Glazing (SSG): Engineering All-Glass Facades for Australian Commercial Buildings

Structural silicone glazing (SSG) is the technology behind many of Australia’s most recognisable modern buildings. By bonding glass to a metal frame with high-strength silicone adhesive, SSG eliminates exterior caps and covers, creating smooth, all-glass facades with uninterrupted reflections and clean sightlines. From Sydney’s commercial towers to Melbourne’s mixed-use developments, SSG has become the signature of premium architecture. This guide explains how SSG works, where it is used, how it is tested and what Australian specifiers need to know to deliver compliant, durable structural glazing.

What Is Structural Silicone Glazing?

Structural silicone glazing is a curtain-wall construction method in which glass or other panels are adhered to a supporting frame using a structural silicone sealant. The sealant carries the dead load of the glass and resists wind loads, while also providing weatherproofing and accommodating movement. Unlike traditional captured glazing, where glass is held by pressure plates and cover caps, SSG relies on the bond between silicone, glass and aluminium.

There are two main forms:

1. Two-sided SSG: Structural silicone is used on two sides of the glass panel, typically the vertical edges, while the horizontal edges are captured with pressure plates and cover caps.
2. Four-sided SSG: The glass is bonded on all four edges, creating a fully frameless appearance from the exterior. This is the most visually dramatic option but also the most demanding from an engineering standpoint.

The silicone used is a two-part, neutral-cure structural silicone specifically formulated and tested for structural glazing. DowCorning 983, Sika SG-500 and similar products are common in the Australian market. These silicones are designed to maintain adhesion and elasticity for decades while resisting UV radiation, temperature extremes and moisture.

Why Architects Specify SSG

The primary reason for specifying SSG is aesthetics. Removing visible caps creates a continuous glass skin that reflects sky and surroundings, giving buildings a sleek, contemporary appearance. Other benefits include:

• Improved thermal performance: Eliminating external metal caps reduces thermal bridging at the glass edge.
• Reduced water penetration: A properly designed SSG joint has fewer exposed horizontal ledges and cap joints where water can collect.
• Faster installation: Prefabricated unitised panels with factory-applied silicone can be installed quickly on site.
• Design flexibility: SSG can be used with flat, curved, sloped and even cold-bent glass.

For architects and developers competing for premium tenants or buyers, an SSG façade signals quality and sophistication. It is frequently specified for corporate headquarters, five-star hotels, luxury residential towers and flagship retail projects.

The SSG System Components

A complete SSG assembly includes several engineered components:

The structural silicone joint is designed with a specific width-to-depth ratio, typically 2:1, and a minimum bite (contact width) determined by structural calculations. A common minimum bite is 9 mm for small panels in low wind zones, increasing to 12 mm, 15 mm or more for large panels in high wind or high-rise applications.

Australian Standards and Compliance

SSG in Australia must comply with multiple standards and codes:

• AS 2047: Windows and external glazed doors in buildings. While AS 2047 primarily addresses windows and doors, curtain-wall systems are often tested to related performance criteria.
• AS 1288: Glass in buildings—Selection and installation. This standard governs glass type, thickness, human-impact resistance and safety glazing requirements.
• AS/NZS 1170: Structural design actions, including wind loads (Part 2) and load combinations (Part 0).
• AS/NZS 4284: Testing of building facades. This standard defines the test methods for air infiltration, water penetration and structural capacity of curtain walls.
• ETAG 002 / EOTA guidance: European technical approval guidelines for structural sealant glazing kits, often referenced by Australian silicone manufacturers for product assessment.

Because SSG is a performance-critical system, most projects require project-specific engineering certification. The certifier or façade engineer will verify:

• Silicone joint dimensions and structural bite.
• Glass thickness and type for wind and impact loads.
• Frame deflection limits.
• Movement accommodation for thermal expansion and inter-storey drift.
• Compatibility between silicone, glass coating, primer and frame finish.
• Quality assurance and installation procedures.

Structural Silicone Selection and Testing

Not all silicones are suitable for structural glazing. The sealant must be:

• Formulated and branded as a structural silicone by the manufacturer.
• Tested for adhesion to the specific glass and aluminium substrates.
• Capable of maintaining tensile strength of at least 0.345 MPa under sustained load.
• Resistant to UV, ozone, temperature cycling and moisture.
• Compatible with any Low-E coatings, frits or ceramic paints on the glass.

Before fabrication, the applicator must conduct adhesion testing on samples of the actual substrates using the proposed cleaning and priming procedure. This is usually documented in a project-specific adhesion test report. Ongoing quality control during production includes:

• Peel-adhesion tests on fabricated panels.
• Measurement of sealant dimensions.
• Visual inspection for voids, bubbles and contamination.
• Record of environmental conditions during application and curing.

Glass for SSG Facades

Glass selection is critical for both safety and longevity. Heat-soaked toughened glass is the most common choice for monolithic SSG panels because it reduces the risk of spontaneous breakage from nickel sulphide inclusions. Laminated glass is used where post-breakage retention is required, such as overhead glazing, spandrels or high-rise barriers.

Common glass configurations include:

• Single toughened: 10–15 mm heat-soaked toughened for low-rise and non-critical applications.
• Double-glazed units: Two lites of toughened or heat-strengthened glass with a coated inner surface, argon fill and warm-edge spacer.
• Laminated panels: Two or more glass plies with PVB or SentryGlas interlayer for safety and acoustic performance.

The outer lite of an SSG unit is often heat-strengthened rather than fully toughened because heat-strengthened glass breaks into larger pieces that may remain in the frame longer after damage, reducing fallout risk. Project-specific engineering determines the appropriate glass type.

Unitised vs Stick-Built SSG

SSG facades are installed using one of two methods:

Stick-built systems are assembled piece by piece on site. Aluminium mullions and transoms are erected first, then glass panels are lifted into place and bonded. Stick-built SSG offers flexibility for complex geometries but is slower and more weather-dependent.

Unitised systems are factory-built panels that include the frame, glass, silicone, insulation and sometimes finishes. Completed panels are shipped to site and clipped onto the building structure. Unitised SSG is faster, offers better quality control and reduces site labour. It is the preferred method for high-rise towers and projects with tight schedules.

MEICHEN’s commercial aluminium systems include curtain-wall and unitised façade solutions engineered for Australian wind loads and thermal requirements. The company can supply prefabricated panels or stick-system components depending on project needs.

Thermal Performance and Condensation Risk

SSG can improve thermal performance compared with capped systems because the exterior metal cap is eliminated, reducing cold bridges at the glass edge. However, the aluminium frame behind the silicone remains a potential thermal bridge. To address this, specifiers should:

• Use thermally broken aluminium framing behind the silicone.
• Specify double-glazed units with Low-E coatings and argon fill.
• Use warm-edge spacers to reduce edge-of-glass heat loss.
• Model thermal bridging with tools such as THERM or Psi-modelling software.

Condensation on the interior frame or glass edge indicates that the surface temperature has fallen below the dew point. In air-conditioned buildings, this can lead to mould, finishes damage and indoor air-quality issues. Proper thermal break design and warm-edge spacers are essential for SSG in Australian commercial buildings.

Movement, Drift and Durability

High-rise buildings move. Wind sway, inter-storey drift, thermal expansion and concrete creep all impose movement on the façade. SSG systems must accommodate this movement without over-stressing the silicone or glass.

Typical design allowances include:

• Inter-storey drift: Commonly ±1/500 of storey height, or as specified by the structural engineer.
• Thermal movement: Aluminium expands at approximately 24 × 10⁻⁶ per °C; glass expands at approximately 9 × 10⁻⁶ per °C.
• Building settlement: Differential movement between primary structure and façade.
• Sealant movement capability: High-performance structural silicones accommodate ±25% to ±50% joint movement.

The silicone joint must be detailed so that movement is shared across the joint and not concentrated at corners or panel edges. Mock-up testing and independent façade engineering review are common on large SSG projects.

Maintenance and Inspection

SSG facades require periodic inspection to ensure long-term performance. A typical maintenance program includes:

• Annual visual inspection of silicone joints for cracking, debonding or discolouration.
• Checking drainage weeps and pressure-equalisation chambers.
• Inspection of glass for cracks, chips or coating damage.
• Testing of adhesion in suspect areas by a qualified applicator.
• Replacement of damaged panels by trained installers using approved silicone.

The expected service life of a quality structural silicone joint is 25–40 years, depending on exposure and maintenance. Major refurbishment may involve removing and replacing silicone joints while retaining the original glass where possible.

MEICHEN Structural Glazing and Curtain-Wall Capabilities

MEICHEN Windows & Doors supplies aluminium curtain-wall, commercial window and unitised façade systems for Australian projects. The company’s BA150 series and related commercial suites are engineered for high wind loads, large spans and structural glazing applications.

MEICHEN’s SSG-related capabilities include:

• BA150 curtain-wall suite: A 150 mm box-section framing system with high section modulus for tall buildings and large glazing spans.
• Thermal-break options: Polyamide strips to reduce thermal bridging behind structural silicone joints.
• Custom extrusion and CNC fabrication: Precision-machined transoms, mullions and pressure plates.
• Glass scheduling: Coordination of heat-soaked toughened, laminated and double-glazed units with Australian glass processors.
• Project engineering support: Shop drawings, structural calculations, façade movement studies and export documentation.

MEICHEN’s commercial systems have been used in Australian apartment towers and mixed-use projects where high wind loads, water resistance and architectural performance are required. The company works with local façade engineers and certifiers to ensure SSG designs meet AS 1288, AS/NZS 1170, AS/NZS 4284 and project-specific performance criteria.

Cost and Procurement Considerations

SSG is a premium façade solution. Costs typically range from AUD 1,200 to AUD 2,500 per square metre installed, depending on panel size, glass specification, building height, access constraints and project location. Unitised systems generally cost more per panel but save time and site labour. Stick-built systems may be more economical for low-rise or geometrically complex buildings.

Procurement should include:

• Project-specific structural silicone adhesion testing.
• Fabrication quality-assurance plan.
• Independent façade engineering review.
• Site installation supervision by the silicone manufacturer or accredited applicator.
• Warranty documentation covering silicone, frame and glass.

Frequently Asked Questions

1. How long does structural silicone last on a building façade?
Quality structural silicones are designed to last 25–40 years with proper installation and maintenance. Service life depends on exposure, UV intensity, temperature cycling and whether the joint was correctly primed and applied.

2. Can SSG be repaired if the silicone fails?
Yes, but repairs must be carried out by trained applicators using silicone from the same manufacturer as the original. Failed silicone is cut out, the substrates are re-prepared, and new silicone is applied. In some cases, the glass panel must be removed and re-bonded.

**3. Is structural silicone glazing safe in high winds?
Yes, when engineered correctly. SSG systems are designed and tested to resist the wind loads specified in AS/NZS 1170.2, with safety factors appropriate for the building importance level. Large projects often undergo full-scale facade testing to AS/NZS 4284.

4. What is the difference between structural silicone and weatherproof silicone?
Structural silicone is formulated to transfer loads and maintain adhesion under long-term stress. Weatherproof silicone is designed only to seal against air and water. They are not interchangeable. Structural glazing must use a silicone explicitly rated and warranted for structural glazing.

5. Can SSG be used on sloped or curved glazing?
Yes. SSG is frequently used for sloped glazing, skylights and curved facades. These applications require additional engineering to address gravity loads, water drainage and thermal movement. The silicone manufacturer and façade engineer should review the design.

Conclusion

Structural silicone glazing represents the intersection of architecture, engineering and materials science. When executed well, it delivers stunning all-glass facades with excellent weather resistance and thermal performance. Australian specifiers must navigate a complex web of standards including AS 1288, AS/NZS 1170, AS/NZS 4284 and project-specific adhesion testing. By selecting experienced suppliers, qualified applicators and certified aluminium systems, developers can realise SSG projects that are beautiful, durable and compliant. MEICHEN’s commercial curtain-wall and façade systems provide Australian projects with a reliable source for engineered aluminium framing, glass scheduling and technical documentation in the demanding SSG market.