Ask the Expert (Guardrails)

How do we specify glass railings?

• By Dan Stachel
• 06/01/19

Glass design and engineering analysis can be inconsistent across projects. There are several possible reasons for this including the treatment of guardrails as a product rather than an engineered structure, general inexperience with glass as an engineered material, and limited access to glass design software in the U.S.

To ensure you have all the pertinent details, ask suppliers to provide you with a comprehensive proposal, including detailed takeoffs with specific inclusions or exclusions for each railing style within the project scope. These details should include aspects such as finish, linear footage, structural attachment, and makeup. Additionally, request a submittal package that includes 3D renderings based on the architectural and structural specifics for the project.

High-definition surveying (HDS) technology offers tremendous benefits over conventional surveying. It allows for the capture of thousands of critical measurements with precision accuracy, thereby significantly reducing the need for fabrication rework. It also offers a much faster track to the manufacturing process by eliminating the risk of human error and saving weeks of manual field measuring.

Regardless of the method selected for analysis, there are two key principles that should be considered when specifying glass railing: the elastic properties of laminate interlayers (and how they change with temperature and load duration), and understanding that local stresses—e.g., contact materials, support size, and hole size—are critical. In light of these varying factors, it’s recommended that a good finite element program be used to accurately determine glass stresses instead of any manual analysis.

Glass analysis is the most critical aspect of specifying point-supported glass due to life-safety factors. It’s essential that those who have a stake in a project understand this and take appropriate measures to ensure that building code requirements are met.