Is top railing required for a glass railing system? If it is monolithic tempered glass, the simple answer is “yes,” according to the International Code Council (ICC). (The 2015 International Building Code has added an exception that permits the elimination of a top rail if laminated, tempered glass is used, and it is approved by the local code official.)

However, it’s not difficult to find glass railing installations where glass balustrades are in place with an exposed glass edge at the top of the guard. So, what is causing this disconnect between the code requirement and actual installations?

In some cases, the lack of a top rail is based on confirming that the glass railing system meets the structural requirements. However, for the most part, it’s based on ambiguity in the older code language.

Previous International Building Code Requirements

Prior to 2015, the International Building Code (IBC) relating to glass railing stated the following:

IBC 2407.1.2 Support. Each handrail or guard section shall be supported by a minimum of three glass balusters or shall be supported to remain in place should one baluster panel fail. Glass balusters shall not be installed without an attached handrail or guard.

The intent of the code was to protect the public in the event of an individual panel’s failure. Should one lite of glass fail and vacate the opening, a minimum of two panels would remain in place to hold the “attached handrail or guard” and thereby assist in preventing falls.

The ICC requires guards in areas where there is a minimum drop (generally 30”) on one side. Guardrails have a minimum height requirement of 42” in commercial applications and 36” in residential applications. Handrail is required on stairs and must be located between 34”-38”. If a stair meets the minimum drop as noted in the code, then a guard with a handrail is required.

This problem began with the interpretation of one sentence of the code, “glass balusters shall not be installed without an attached handrail or guard.” Many installers, designers, and inspectors interpreted this sentence to indicate that as long as a handrail is in place, the code has been met.

The use of the word “guard” in this code is incorrect. The ICC defines a “guard” as a structure put into place to prevent an accidental fall. In our opinion, it was meant to state that glass balusters shall not be installed without an attached handrail or top rail. The ambiguity of that wording resulted in the installation of glass railings without a top rail but with a handrail.

Unless it’s a stairway, a handrail is not required. Often, adding a handrail to a level guard was to meet an interpretation of the wording included in the 2009:

It was easy to see how this interpretation might have been made, but what was being neglected was the structural requirements set out in the previous paragraph:

IBC 2407.1.1 Loads. The panels and their support system shall be designed to withstand the loads specified in section 1607.7. A safety factor of 4 shall be used.

Cross-referencing to section IBC 1607.7 regarding design loads we find this:

IBC1607.7.1 Handrails and guards. Handrail assemblies and guards shall be designed to resist a load of 50 pounds per linear foot (pound per foot) (0.73 kN/m) applied in any direction at the top and to transfer this load through the supports to the structure.

IBC1607.7.1.1 Concentrated Load. Handrail assemblies and guards shall be able to resist a single concentrated load of 200 pounds (0.89kN), applied in any direction at any point along the top, and have attachment devices and supporting structures to transfer this loading to appropriate structural elements of the building.

And herein lies the rub. IBC1607.7 clearly states that the load must be met by the top of the guard. The bare edge of half-inch, monolithic glass balusters cannot meet the 800-pound (4 times 200-pound) concentrated load. In the event of one panel’s failure, a railing must remain at the top of the guard that meets the load requirement. An attached handrail will not meet this requirement as it would be placed at a handrail height of between 34”-38” not at the 42” minimum guard height. If the glass is shattered, the remaining handrail does not meet the guard requirement.

To further reinforce the ICC’s position, an exception was added to the 2009 IBC, which permitted the elimination of a top rail if laminated, tempered glass was used.

2015 International Building Code Requirements

The definitive answer now exists in the 2015 IBC with the key addition that a top rail is required unless laminated, tempered glass is used and it is approved by the local building official. Further, the 2015 IBC now requires the use of laminated, tempered glass in all railing applications.

Section 2407.1.2 Support. Each handrail or guard section shall be supported by a minimum of three glass balusters or shall be otherwise supported to remain in place should one baluster fail. Glass balusters shall not be installed without an attached handrail or guard.

Exception: A top rail shall not be required where the glass balusters are laminated glass with two or more glass plies of equal thickness and the same glass type when approved by the building official. The panels shall be designed to withstand the loads specified in Section 1607.8.

Even with this definitive code, one final thing to bear in mind is that the IBC codes are “model codes”. Your area may have yet to adopt the most recent model code. The best advice is to consult with your local Authority Having Jurisdiction to confirm what has been adopted in your area.