Structural Glazing

Structural Silicone Glazing (SSG)

StoneCrop new build structural glass facade

Structural Silicone Glazing is used to create large frameless glass walls or façade designs. Many of IQ’s highly bespoke projects involve designing oversized structural glass elevations and using industrial strength silicone to create slim joints between each glass unit. This article discusses the different kinds of structural silicone glazing options out there, including what to look out for when specifying SSG on your project.

What is structural silicone?

Structural silicone glazing is often used as a modern alternative to curtain walling, as it allows for extremely minimal designs with a frameless look. It enables architects to design structural glass facades in any number of shapes and sizes without needing to include bulky frames and joints that detract from the minimal aesthetic.

Silicone sealants fulfil several functions; they act both as a weather seal and as a structural bonding element. This means that glazing beads or other protective and supporting elements do not need to be used.

Water End House frameless structural glazing

Glazing installations using structural silicone joints

Structural silicone can be used to create any number of frameless structural glass installations. These include:

  • Glass to glass corners

Silicone is also used as a sealant for glass-to-glass joints in fire-rated glazing installations. A thermoplastic spacer is specified for these installations, with a 6-8mm silicone joint.

Frameless glass beams, fins or steel support sections may also be required in certain instances. Glass roofs that exceed a span of 1.2m and glass walls over 3m tall will require additional support.


What is the best kind of SSG?

There are a range of different brands of structural silicone on the market. IQ uses black Dow Corning high modulus silicone as standard on all of our structural glass applications.

This industrial strength structural silicone is the highest quality version on the market. It comes with a 25 year guarantee, provided by Dow Corning and cures to create a durable, fully waterproof seal.

Opting for high quality silicone also ensures a high thermal resistance and air tightness, key factors in minimising heat loss in any glazing installation.

It is worth checking the life expectancy and performance of the chosen silicone brand when receiving a quote from a glazier, as this can vary from as little as 5 years.

Frameless Glass Design

Minimal silicone joints

IQ use black structural silicone as standard in our glazing applications. Using black structural silicone matches the black finish of the spacer bars and other glass fixings. This ensures a neat, tidy joint with concealed fixing details.

This can, however, be customised for projects that would like the silicone joints to match other glazed elements that might be powder coated in another colour. For the Story of Gardening project, light grey silicone was specified to match the silver stainless steel frames of the oversized glazed elevations.

Frameless glass walls story of gardening museum

Silicone drying time

Once structural silicone is applied to a structural glazing installation, it needs to cure.

During curing, the chemical structure of the silicone changes in response to exposure to oxygen. This process forms a rubber compound which acts as a strong weathertight seal between the two glass units.

The curing time for the silicone used by IQ is 3mm per day, assuming fair weather conditions. This normally comes out at approximately 1-2 weeks.

You may also hear the term drying time being used – this refers to the initial evaporation of moisture, which leaves the silicone dry to the touch, rather than the longer curing process.

South West London glass box extension on top floor

Get in touch

For expert advice on how to incorporate bespoke, frameless glass design into your project, get in touch with the team at Or, give us a call at  01494 722880.

Further Reading

What is structural glazing

Invisio structural glass product page

Guide to glass box extensions

How to Incorporate Oversized Glass in your Design