Sizes of Structural Glazing for Commercial Applications
Structural glazing has many advantages thanks to the large sizes that are possible from the bespoke glass structures. These large glass constructions have many applications and are used on high specification architectural designs all over the world.
Understanding what sizes of structural glass assemblies available is an important step in specifying structural glass successfully. There are many areas to consider including performance, access and logistics.
So what size can structural glass be?
Minimum and Maximum Sizes of Structural Glazing
In isolation, the maximum size of structural glazing depends entirely on the glass manufacturers. Float lines and toughening plants are constantly increasing their capacity for larger structural glass sizes to answer the market’s call for bigger and better structural glass assemblies. At this moment in time the standard glass stocked in the UK suitable for structural glazing is 6m x 3.2m,
however panes up to 20m x 3.2m can be ordered bespoke from glass suppliers for special projects.
The Newt development in Somerset is an excellent example of the sizes that structural glass can go to. The size of the structural glass elevation at the Story of Gardening Museum was 6 meters at
its highest point. This structural glass wall would have been able to be sourced from stock in the UK. Whereas the 20 metre wide glass window used elsewhere on the project had to be ordered bespoke directly from the glass manufacturer.
But when considering the sizes of structural glass you can’t just think of them in theory. These extremely large frameless glass units have to be able to get to the point of installation and the building site. Access issues, restrictions on vehicle weight and other obstructions may all contribute towards the possible sizes of a structural glass assembly. When IQ begin to look at a structural glass project, we look at the project as a whole to allow us to consider these types of logistical considerations early on in the process which helps frame the design conversation.
There are also minimum sizes of structural glazing to consider. The minimum size of structural glass is more a consideration of the ratio of width to height of the glass panel. Toughened safety glass as used in structural glass and glazing cannot be too narrow or it becomes fragile and brittle. The actual minimum size of structural glazing will also depend on the thickness of glass but the team at IQ can advise on this on a project by project basis.
Structural Glass Beams & Structural Glass Supports
Large structural glass installations, where huge pieces of glazing are not possible, can be created by using multiple structural glass units that are connected together. For example, you could create a large glass facade that is made of multiple glass units connected together with silicone joints.
The Lea Bridge library glass facade is an excellent example of that, where panels of structural glass were used along the entire length of the library extension with silicone joints vertically between each panel. With frameless hidden fixings at the head and the base of the glass units, the minimal silicone joints allowed us to create a large structural glass wall with no visible framing.
It is possible to create frameless silicone joints within a structural glass facade with no internal supports up to six meters tall. Over the height of 6 metres it will depend on the wind load of the project as to whether an internal T section or glass fin will be required to provide wind stability to the glass facade.
The structural glass facade to the front elevation of our head office uses internal aluminium T-sections to support the silicone joint. These aluminium extrusions are specifically designed for the Invisio facade system to sit directly behind the silicone joint and not to increase the sight line you see externally. Internally, you see a slim and elegant metal fin that runs the full height of the glass joint.
When silicone joint connections are used within a structural glass roof you may also have to consider the internal support. Internal support below a structural glass roof is a more common sight due to the angles that structural glass roofs sit at. Where the multiple glass units meet within the glass roof, a silicone joint is still used to connect them however, a glass beam or steel section (or similar form of supporting structure) is then required underneath the silicone joint to provide support. Typically, any glass joint that is over 1.3 metres in a glass roof will require some additional support beneath it. However, this is not a hard and fast rule.
Take for example the floating glass meeting room at our showroom in Amersham.
The floating glass meeting room is almost 4 metres wide and when designing we were sure we wanted no steel beam or glass beam below the silicon joint. In addition, the access to the building and the fact that the glass meeting room is inside meant that it wasn’t feasible to install one panel of glass as the entire glass floor. It simply wouldn’t have fitted into the building.
In order to ensure that we didn’t require a glass beam or steel section underneath the glass joint, we conducted some glass modelling. The results showed us that if we increased the specification of the glass floor no supporting member would be required beneath the silicone joint. The result is a four metre long silicone joint with no support and a completely frameless floating glass box which is a pinnacle aspect of our glazing showroom in Amersham.
Where internal supports are required within a structural glass roof there are many design options but a glass beam or a steel section or box are often the most popular or design choices.
The glass atrium we created at Great George Street in Bristol showcases the use of glass beams to support the large glass roof. Whereas the glass roof at the Beech House in Beaconsfield is an example of where we use steel sections to support the glass roof which better suited the interior design.
For those looking for a timber design, the glass roof at Chicheley Hall is a great example of using timber to support the inside face of a structural glass roof. This complicated structural glass assembly was attached to listed 16th century barns and the additional steel supports you can see were due to the fact that the structure had to be self-supporting.
There are many different options when looking at supports for structural glass. The team at IQ can help to advise which would be most suitable for the project and what might be possible.
How Thick Is Structural Glazing?
The overall thickness of structural glazing will depend on the specification of glass that’s required. We determine the specification of glass needed by looking at both the size of the structural glass assembly and the performance that is required. Projects with higher wind loads will require a slightly thicker structural glass unit to allow for deflection under high wind loads. Projects that require elevated levels of acoustic dampening may require a special laminated layer which would increase the thickness of the glazing.
It is impossible to determine the thickness of a structural glass unit without properly looking at the project and assessing the project requirements. However due to the nature of certain structural glass assemblies they will have a thicker construction than others. A structural glass roof will have a minimum thickness of 33 millimetres for a single glazed unit whereas a double glazed structural glass facade could start with a glass thickness of 32 millimeters or double glazed unit.
What Next?
If you are looking at designing a structural glass assembly and our looking at the possible sizes of structural glazing the team and IQ can assist. Just get in touch with the team here by telephone or e-mail and a member of the technical sales team will be in touch to discuss the project requirements.
If the design of bespoke glass facades is interesting to you or your practice you may also be interested in booking our bespoke glass facade CPD.
Shannon Normoyle
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