Innovation Drivers: Considerations for Durable, Safe Glass Railings

By Florian Doebbel

Wherever we go, modern architecture is eagerly dematerializing design, increasing transparency and creating views of its surroundings. This desire met railing systems a long time ago and has been expanding the popularity of frameless glass railings, which are supported only by a base shoe at the bottom edge of the glass unit.

Full transparency of frameless glass railing applications has become essential for every unique stadium and shopping mall experience. Railings have gained even more attention in residential highrise projects, where balconies are considered social connectors. Instead of creating fences or concealing barriers, the intent is to maximize transparency for connecting residents with the outdoors and the neighborhood.

Standards and Changes

The ongoing success of frameless glass railings is not just driven by architectural needs, but also by new materials and updated standards significantly increasing performance, post-breakage safety and the acceptance of project owners and building users. The 2015 version of the International Building Code (IBC), section 2407 requires the use of fully tempered laminated glass or at least heat-strengthened laminated glass in certain railing applications. While the market offers various types of flexible and stiff laminate interlayers, any different combination of glass type, glass thickness, interlayer and glass support provides a specific post-breakage performance tested according to ASTM E 2353 Standard Test Methods for Performance of Glazing in Permanent Railing Systems, Guards, and Balustrades.

The 2018 IBC will take into account the different post-breakage performance of specific laminated glass units and supports. Based on this, an attached top rail or handrail is not mandatory any more if certain conditions are met. The laminated glass panels must be tested and remain in place as a barrier following impact resistance or glass breakage in accordance with ASTM E 2353. This is another way to improve transparency while focusing on the structural design on the laminated glass interlayer and the base shoe configuration.

While new standards and materials drive innovation in architecture, design
and performance, they challenge traditional ways of handling and installing accident-resistant glass units. Proving and maintaining sufficient post-breakage performance requires durable structural properties of the laminated glass interlayer as well as a strong and appropriate support of the laminated glass unit.

Concentrated stress increases the risk of glass breakage and the creeping of
the laminate interlayer. Any interlayer creep can loosen the clamped glass unit or cause delamination. A continuous and uniform support that’s able to accommodate tolerance between the glass unit and base shoe is required. In addition, grouts used in wet-glazed systems should be limited in adhesion and rigidity to compensate thermal dilatation between the glass unit and base shoe without over-stressing any of the components.

If systems are wet glazed, it’s important to verify the compatibility of the
caulk, grout, blocks and sealant used in contact with each other and with the
laminated glass interlayer. To prevent negative effects, our company suggests that the grout be fully cured before applying the sealant cap joint. We’ve also seen cases where traditional methods of setting monolithic glass in railings, such as cement-based grouts, may be incompatible with laminated glass. Especially for outdoor applications, the ability of
porous cement-based grouts to absorb liquid water can lead to permanently wet and alkaline conditions in the base shoe, which could discolor and delaminate the laminated glass interlayer.

Water is another risk factor in outdoor glass railing applications. While stagnating liquid water can cause discoloration and delamination of the interlayer, frozen water enclosed in the base shoe expands its volume and can cause over-stressing or even breakage of the glass units. That means any outdoor applied system requires a watertight base shoe, including a cap joint guiding water away from the glass unit and the base shoe. Any outdoor applied dry-glazed base shoe needs to be set up with a suitable drainage system.

Railing Grouts

Due to today’s variety for materials, shapes, structural demands and individual designs, the wet-glazed installation method is often the preferred technique for many commercial projects. Combining the above-mentioned needs with the advantages of a wet-glazed system, a new generation of polymer-based railing grouts has been developed. The polymer-based railing grouts provide improved compatibility with laminate interlayers, and also enable strong support and controlled flexibility. The curing system does not bring any water into the base shoe. It ensures a controlled, uniform and chemically triggered curing process. The completely filled base shoe, finished with a silicone cap joint, provides a watertight system to keep water away from the interlayer and ice out of the base shoe.

With polymer-based materials, we can also learn from the manufacturing industry and improve the installation process. Based on project conditions, self-leveling and non-sagging product types can be used. Also available are slow- and fast-curing systems, as well as options for manual processing, machine-supported mixing and dispensing or pre-packed and cartridge solutions. For the majority of larger projects with horizontal railing
set-ups, the use of a self-leveling version and a machine-supported mixing and dispensing equipment can help reduce waste material and improve productivity of the installation and rail-routing process compared to manual applications.

Glass railing design and installation has seen evolution in safety, resistance,
durability, optimization and productivity, helping extend service life and
improve sustainability of modern frameless glass railing systems.

Florian Doebbel is business development manager for facades at
Sika U.S. He is based in Lakewood, N.J.

To view the laid-in version of this article in our digital edition, CLICK HERE.