The term ‘structural glass’ refers to any type of load-bearing glazing. In place of a traditional wall, made of materials such as bricks, large panels of thick toughened glass are installed. There are lots of ways to integrate structural glazing into building design, including walls, doors, roofs, and floors.
The glass is an integral structural element, bearing weight horizontally and vertically with minimal additional support. Glass beams or fins, steel struts, spider fixings, and silicone sealants can be used to secure the glass panels without being too visible. This creates a practically frameless appearance.
The location, environment, and intended purpose of the structural glass will determine the size, shape, thickness, and bonding mechanism. This has to be carefully calculated, because structural glazing must withstand a variety of stresses, from wind and temperature changes to physical loads.
One of the biggest benefits of structural glazing is that the lack of framing systems gives architects and designers more opportunity to create truly stunning installations of glass for their buildings. This allows a much wider scope and greater flexibility in creating a completely bespoke design.
The only factors restricting the maximum size of structural glass panels are your budget and site access limitations. The thickness of the glass will help to increase the building’s energy efficiency, with thermal technology maintaining an ambient temperature instead of trapping too much heat.
Large expanses of glass are eye-catching from the outside and offer unrivalled open views of the surrounding area from the inside. Not only does it physically increase usable interior and exterior space, but it also tricks the eye into thinking it’s even more spacious due to the flood of light.
There’s a lot of in-depth engineering involved in a successful structural glazing installation. The physical performance of each glass panel is far more important than how it looks, which is why so many calculations go into ensuring that your bespoke glazing is structurally sound.
Factors that require extensive consideration when selecting structural glass qualities include:
- Thermal insulation
Structural glass is given a ‘Ug’ value according to the amount of thermal energy that can pass through the centre of the pane itself. The lower the value, the better the insulation; you should never go for glass with a Ug value of more than 1.2 W/m2K for structural glazing.
Th ‘Uf’ value refers to the thermal performance of the framework, while ‘PSIG’ indicates the performance of glazing spacers. These can all be combined into an overall ‘Uw’ value, sometimes referred to as simply the U value, using test methods standardised by BS EN 673:1998.
- Acoustic reduction & fire rating
You may be familiar with seeing sonic insulation ratings in decibels, but acoustic reduction values are represented by an ‘Rw’ figure for structural glass. Decibels measure acoustic power, and hertz measure vibration frequency; both go into the calculations for Rw standardised by EN ISO 717-1.
As for fire-rated glass, it needs to be fire-tested at its full size as per the intended installation before it can be used for structural purposes. Any fixings will also need to be fire-rated. You can find out more about how fire ratings for glass work on our Fire Rated Glass Partitions & Doors page.
- Line load & maintenance load
Since the glass is expected to bear a heavy structural load, your design must be tested to ensure that it meets all the necessary load-bearing requirements. You cannot legally install structural glass that is not fit for purpose due to the obvious safety risks, which is why prior testing is mandatory.
Vertical glass panels must be able to withstand a particular line load – like the weight of a person leaning on a glass barrier. The glass specifications and fixings must bear the appropriate load for its intended purpose. The same applies for horizontally installed panels, which must be able to bear an adequate maintenance load – such as the weight of a person accessing a roof for repairs.
Exterior walls and facades will also need to withstand a wind load of no less than 0.5kN to ensure that the structural glass won’t crack, bow, or break under the pressure of strong winds. Buildings by the coast or at high altitudes are likely to have much higher wind load requirements.