A code contradiction
Is a top railing required for glass railings? According to the International Code Council, Washington, D.C., the simple answer is yes. Additionally, in the event one baluster panel fails, the railing must meet the building code’s load requirement for guards, according to the ICC.
However, there are plenty of glass railing installations with balustrades with an exposed glass edge at the top of the guard. What is causing this disconnect between the code requirement and actual installations and who will be liable in the event of a failure that results in injury? The International Building Code relating to glass railing states 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 inches—on one side. Guardrails have a minimum height requirement of 42 inches above the walking surface in commercial applications and 36 inches in residential applications. Handrail is required on stairs and is located between 34 and 38 inches. If a stair meets the minimum drop as noted in the code, then a guard with a handrail is required.
This problem begins with the interpretation of the phrase: glass balusters shall not be installed without an attached handrail or guard. Many installers, designers and inspectors are taking this sentence to indicate that as long as a handrail is in place, the code has been met.
The photo shows an installation at the newly renovated Terminal 3 at O’Hare International Airport in Chicago. This is a guard application with no top rail and an attached handrail. Since this is not a stair, the handrail is not required by code. It has been included in an attempt to meet IBC 2407.1.2 by including an attached "handrail” in lieu of an attached “guard."
It is easy to see how this interpretation can be made in reading IBC 2407.1.2 but what is being neglected is the requirement set out in the previous paragraph – IBC 2407.1.1:
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 structure 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 (42 inches). Glass balusters will not be able to meet the 800 pound (4 times 200 pound) concentrated load without an attached guard rail. And 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.
It should be noted that the four times design load requirement is unique to glass railing. Per ASTM E 935 Standard Test Methods for Performance of Permanent Metal Railing Systems and Rails for Buildings, metal railing systems are only required to be tested to 1.65 times design load. The significantly larger safety factor for glass railings is a reflection of the concerns of the code bodies in relation to safety for glass railings.
To further re-inforce the ICC’s position, a request for an exception was considered during the most recently completed code review cycle. The result was that for the 2009 publication of the IBC, the top rail requirement for glass balustrade systems will no longer be required if laminated, tempered glass is used for the balustrade. This will allow for the installation of glass railing that meets the designer’s desire for a completely unobstructed view while still providing a safer, code compliant guardrail.