Structural Glass Balustrades; types and methods

Why a balustrade is named a “structural glass” balustrade? And what differentiates it from other types of balustrades?

The answer is simple enough yet there are many methods to actually implement this type of solution.

When glass of a balustrade is not just used as an infill panel but is also used as the actual structure of the balustrade it is often referred to as a structural glass balustrade. It also sometimes referred to as a frameless glass balustrade or a cantilevered glass balustrade.

The basic idea is simple and the same throughout all types of structural glass balustrades and is based on two engineering principles; a strong base that can clamp the glass panel with thick and strong glass panels that can resist the bending moments and loads imposed on it.

Whilst having no handrail is a very appealing trend and looks very nice, use of a handrail seems to have become “optional” by some suppliers in the market despite the fact that it is required by law to meet current UK building regulations. The handrail or top section that is placed on the glass is meant to tie glasses together at the top, making the entire structure sturdier and more solid. It also must by law be able to withstand the required load if one of the glass panels should break across the gap created.

The base or “shoe” section

The base of the structural glass balustrade, also known in some systems as the “shoe” profile, is the most critical part that requires much design attention. The basic idea is a strong “U” channel either made from two RSAs back to back or using aluminium designed extrusions. The glass gets fixed in place either usually by an epoxy type two component glue or cement type material. As a side note it is interesting to note that in recent years much innovation has gone into these and systems and now you can have base profiles that use pressure screwed clamps or hammered in wedges that can forsake the use of cement or epoxy glue saving on the labour previously involved with setting the glasses, not to mention the dirty process of pouring epoxy into a small channel.

The base profiles can be fixed in various methods to the balcony structure be it steel, concrete or other material. These base profiles and their fixings need to be purpose deigned for every site to endure the loading and fixings can indeed withstand the large loads that will get transferred from the glass panel.

The glass panel

Where most balconies or balustrade systems can utilize 10mm toughened (tempered) glass, structural glass balustrades require a much stronger panel. A minimum thickness of 15mm toughened glass panel must be employed even for residential (single family dwellings) properties. When higher loading requirements are needed, such as public areas, bars, restaurants, discothèques and malls, thicker glass panels are required. 19mm and even 25mm toughened glass panels are employed in these cases.

Because of the thickness of the glass required and the basic iron in standard float glass, when employing regular glass types a greenish type of colour is evident in structural glass balustrades a lot more than regular glass balustrade systems. This can be reduced by using “low iron” glass panels however one should note that these are more expensive.

Using laminated glass on structural glass balustrades

Can laminated glass be used on this type of balustrade? The answer is yes but watch what thickness of glass you use. 17.2mm laminated toughened glass is by far not as strong as 15mm toughened and specific calculations MUST be undertaken before choosing the correct makeup of the laminated panel, sometimes using a combination of heat strengthened on one side and toughened glass on the other side of the laminated panels.

Heat soak test

It is recommended, however not mandatory, to have glass panels used in structural glass balustrades undergo what is known as “heat soak test”. This test eliminates 99% of spontaneous breakage cases that can occur with toughened (tempered) glass. In structural glass balustrades a case of spontaneous breakage can be very dangerous and will also make replacing the glass very expensive, this will usually outweigh the cost of having the glasses heat soak tested and so it is advised to do so.

Weight and self imposed loads

When designing a structural glass balustrade one must take into account the weight of the system and the load the system imposes on the balcony or structure in addition to any other load requirements. A typical structural glass balustrade that uses 15mm thick glass will weigh in the region of 55-60 kg per linear meter and so a ten meter balcony can be over half a ton!

Handrails and top capping

A range of handrails can be used with this type of balustrade, from the simplest “U” capping to fancy elliptical stainless or anodized aluminium handrails. It is important to have a handrail that both looks nice on top of the glass but also has some strength in the shape of it to be able to bridge a gap should one of the glass panels break.

Structural advice

Countless system and methods exist to implement structural glass balustrades; all employ the same basic principle of transferring the load through the glass to a sturdy base channel. Because these types of systems require detailed design and may vary in fixing dramatically from site to site, it is strongly advised to involve a structural engineer before choosing system, fixing method and glass.

Summary

Using structural glass balustrades one can create quite a dramatic statement on a balcony or terrace, having a limitless ability to have just glass as a barrier without the need for any vertical metal elements.

This type of system does not suit every pocket or site conditions but when designed properly is one of the more aesthetic balustrade solutions that exist.