Volume 36, Issue 2, February 2001

Don’t Be Blown Away

Understanding Impact-Resistant Building Code Changes

by Douglas Penn

The requirement for impact-resistant glazing systems continues to grow as new building codes recognize the important role glazing systems play in protecting the structural integrity of a building during a major storm. Studies conducted after Hurricane Andrew revealed that buildings stood a much better chance of surviving a storm if the glazing material remained intact and in the framing system. South Florida responded to these studies by establishing the South Florida Building Code (SFBC), which requires glazing systems to undergo rigorous testing and certification. The code requires that glazing systems located up to 30-feet above the ground be capable of withstanding the impact from large flying debris, and the areas above 30-feet be able to withstand the impact from smaller debris that might be lifted up by storm winds. The testing includes impacting both the aluminum framing system and the glass, and then subjecting the entire system to a cycle test that is designed to mimic the buffeting winds of a hurricane. To pass these tests, the glass must remain in the framing system and not permit any significant openings through which wind and water can pass.
The intent of this new code was to encourage manufacturers to develop glazing systems that did not require storm shutters, yet would provide the desired protection from major storms. A few manufacturers responded to this challenge and developed entirely new systems that enabled architects to meet the new codes and still utilize large expanses of glass in their designs. The new Florida State Building Code and the International Building Code have accepted the wisdom of the SFBC to require passive impact-resistant

So, How Do the New Building Codes Affect You?
Providing full time protection to buildings from flying debris associated with hurricanes results in additional costs for glass and glazing installations. The aluminum system itself must be able to absorb the impact of projectiles and provide glazing details designed to keep the glass in place. These requirements result in aluminum systems that are wider to provide sufficient glass bite, and deeper to meet the structural requirements of the increased design loads, as well as the actual impact. The cost of the glazing material has also increased dramatically, as new materials were developed that would survive the impact and subsequent cycling. Several new laminated products and composites are available, but their cost per square-foot may be as much as ten times greater than conventional glazing materials. In addition, the cost to fabricate and install these new impact-resistant systems is also greater.

The additional cost of supplying and installing impact-resistant glazing systems does not end with the increases in the cost of the material and labor. The cost to provide submittals for a project will also increase. Explicit anchoring details and schedules must be included with your shop drawings. The shop drawings may also have to be reviewed and approved (stamped) by an independent licensed engineer resulting in increased cost and lead time. Copies of certified test reports will have to be submitted to demonstrate that the glazing system, the combination of glass and the aluminum systems, have been tested and will meet the code requirements.

So What Do You Need To Do?
Start by learning more about your local building codes. Codes are changing rapidly and failure to stay abreast of the code requirements may result in a serious financial loss. Even if you do not live or work in coastal areas, local building codes are changing to address inherent shortcomings in structural requirements. For all projects, especially those along the coastline, be sure to review the project specifications carefully. Review the installation instructions from your metal supplier and make sure that all of your personnel understand how to estimate, fabricate and install each system. Monitor field crews to ensure that they are following the anchoring and glazing requirements as the installation may be subjected to approval by a local building official. Failure to install the systems correctly may result in additional labor expense as the building official may require that you remove the system and reinstall it correctly. If you follow these simple guidelines you will be able to make the transition smoothly from conventional glazing systems to those that are designed to provide protection from Mother Nature.


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