Structural Silicone Glazing: How It Works & Where It’s Used

Structural silicone glazing is what makes a glass tower look like one smooth sheet, with no visible frame lines. It’s a bonding method, not a bolt-on accessory, and it changes how a facade handles wind, water, and weight.

This guide breaks down how structural silicone glazing works, the main system types, where builders use it, and what to check before you approve one for a project.

Quick Summary: Structural Silicone Glazing at a Glance

Most guides bury the basics inside long technical manuals. Here’s the short version first.

What Is Structural Silicone Glazing?

Structural silicone glazing (SSG) is a facade method that uses structural-grade silicone sealant, rather than metal clips or pressure plates. It holds glass in place and carries wind and gravity loads back to the building frame.

Instead of a visible aluminum cap gripping the glass edge, the silicone joint does that job from behind. The result is a flush, frameless look on the outside.

Not every silicone qualifies. Only sealant tested, certified, and marketed specifically as structural glazing sealant is approved for this use. General-purpose or acetic-cure silicones are not a substitute.

1. Removes or reduces visible pressure plates and clips
2. Bonds glass directly to the mullion or frame
3. Carries part of the wind load through the sealant joint
4. Works as both a structural bond and a weather seal

How Does Structural Silicone Glazing Work?

Structural silicone glazing works by chemically bonding glass to an aluminum frame. Then letting the cured silicone joint carry structural loads instead of mechanical screws, clips.

The process happens in three stages, whether it’s done in a factory or on-site.

1. Frame and Glass Preparation

The aluminum frame and glass edge get cleaned and primed first. Compatibility testing matters here, silicone, gaskets, and glass coatings all need to work together, or adhesion fails early.

2. Silicone Application and Curing

A bead of structural silicone is applied along the glass edge at a set thickness and width, called the structural bite. As it cures, the silicone changes from a paste into a tough rubber-like bond. A process that typically advances only a few millimeters per day.

3. Load Transfer to the Structure

Once cured, the silicone joint transfers wind. In some designs, dead loads from the glass to the mullion, and from the mullion into the building’s structural frame.

Types of Structural Glazing Systems

There are four main types of structural glazing systems, two-sided, four-sided, unitized, and stick-built SSG. They differ mainly in how many glass edges rely on silicone instead of mechanical support.

1. Two-Sided Structural Glazing

Glass is silicone-bonded on two vertical edges. The top and bottom edges sit in a mechanical frame. This acts as a backup in case the sealant ever fails.

2. Four-Sided Structural Glazing

All four edges are silicone-bonded, with no mechanical backup on any side. This gives the cleanest, most frameless appearance but carries the most risk if the sealant is poorly applied.

3. Unitized Structural Glazing

Glass panels are bonded to frames inside a factory, under controlled conditions. Then shipped to site as complete units ready to hang on the building.

4. Stick-Built (Field-Glazed) SSG

Framing goes up first, and silicone is applied on-site, panel by panel. It’s slower and more weather-dependent than unitized work. So most codes limit four-sided field glazing to repairs rather than new builds.

Where Is Structural Silicone Glazing Used?

Structural silicone glazing is used wherever a project needs a smooth, frameless glass exterior with strong weather resistance.

1. Commercial curtain wall towers and office buildings
2. Hotel and hospitality facades
3. Airport terminals and transit hubs
4. Retail storefronts and shopfronts
5. Skylights and glass roof systems
6. Spider glazing and other frameless glass walls

Structural Silicone Glazing vs Traditional Framed Glazing

Structural silicone glazing trades visible frame lines for a bonded joint. While traditional framed glazing holds glass mechanically with clips and pressure plates on every edge.

Key Benefits of Structural Silicone Glazing

Structural silicone glazing gives architects a cleaner look while also improving how the facade performs against weather and stress.

1. Frameless, modern appearance with minimal visible metal
2. Continuous seal that resists air and water infiltration
3. Even load distribution across the glass edge, reducing stress points
4. Design freedom for large glass spans and curved facades
5. Added resistance to wind pressure when detailed and tested correctly

Builders also like it because it cuts down long-term maintenance costs. There are no clips or gaskets to replace every few years. It also helps buildings pass tighter energy codes, since sealed joints cut air leakage significantly.

Standards and Safety Factors You Should Know

Structural silicone glazing design in North America generally follows ASTM Guide C1401, and existing installations are evaluated against ASTM C1394. 

Sealants and installers should also be checked against certifying bodies such as FGIA and NFRC for thermal and performance ratings.

A key number to ask for is the safety factor, the ratio between the sealant’s ultimate tensile strength and its actual design stress. 

Most approved systems use a 5:1 or 6:1 safety factor. This gives the joint room to handle real-world wind loads without failing.

Maintenance and Inspection Tips

Structural silicone glazing needs periodic in-situ checks, not just a one-time install and forget approach.

1. Check for cracking, chalking, or splitting along the silicone bead
2. Watch for discoloration, which can signal plasticizer migration 
3. Confirm the sealant is still adhering fully to both the glass and the frame
4. Schedule evaluations sooner in harsh climates, coastal salt air, extreme UV, or wide temperature swings

Why Choose Starveil for Structural Silicone Glazing

Starveil is a strong fit for structural silicone glazing projects because we design, cut, and glaze every frame in-house, at our own 45,000 m² factory in Foshan, instead of outsourcing production. See our curtain wall systems for the profiles we build this into.

With 28 years in the industry and more than 1,500 completed projects across 40-plus countries. We’ve built structural glazing systems for climates ranging from Gulf heat to Nordic cold.

1. 28 years of manufacturing experience, one factory, one accountable team
2. Certifications matched to your market: NFRC, CSA, CE, and AS2047
3. In-house design and quality control from shop drawing to installation guidance

Explore our full aluminum window range or read more about our factory before you request a quote.

Final Thoughts

Structural silicone glazing is now a standard choice for any facade that needs a frameless look without giving up weather performance. Getting it right comes down to the right sealant, the right safety factor, a manufacturer who tests every joint before it ships.

Ready to spec structural silicone glazing for your next project? Get a free quote from Starveil and our team will review your drawings within 24 hours.

FAQs

What is structural silicone sealant?

Structural silicone sealant is a high-strength silicone specifically tested, certified, marketed for bonding glass or panels to a building frame. It can carry structural loads and not just seal a gap.

What is 4-sided structural glazing?

4-sided structural glazing is a system where all four edges of the glass are bonded with structural silicone. That too with no mechanical clips or pressure plates on any side.

What are the different types of structural glazing systems?

The main types of structural glazing systems are two-sided, four-sided, unitized, stick-built SSG. Each one differs in how much of the glass edge relies on silicone versus mechanical support.

What is glazing silicone?

Glazing silicone is a general term for silicone sealants used around glass in a window, door, facade. It includes both weather-sealing silicones and, when specifically rated, structural glazing silicones.