Roofing Under Special Codes

By: Ryan VanWert, Director of Engineering

While there is a comprehensive set of building code standards that roofers must be familiar with when executing projects, there are also certain instances when special codes come into play, which can make logistics and installation a bit more challenging for all involved. Of particular note is ICC 500-2014; this special code is typically seen in the design of gymnasiums or gathering areas in schools, and community designated storm shelters. It specifically relates to the wind speed requirements in the design of buildings that have marked storm shelters. As a result, any buildings where a posted storm shelter sign is required must meet some pretty serious requirements. 

You should note that this requirement is only applicable if the local jurisdiction has adopted the IBC 2015 or 2018. The ICC 500 standard is referenced in the 2012 IBC, but the 2015 IBC changes the requirement and includes the design wind speed for tornadoes and hurricanes.  

This code imposes two major factors as it applies to roofing; design wind speed and impact. The maximum design wind speed outlined by ICC 500-2014 most commonly applies to tornado shelters found in the central area of the country. This speed is 250 mph, compared to 120 mph found in standard code requirements. The increased wind speed will ultimately create some extreme uplift pressures on the roofing system. As a result, the roofing system will likely have to show rated pressures produced with an adhered system over a structural concrete deck. Developments are being made in steel deck design to meet the performance requirement, but it is not as common at this point. 

The second major factor that was noted is the impact criteria. Under ICC 500-2014, a horizontal surface such as a roof must be tested to show that the surface can resist a 15-pound 2×4 launched at 67 mph. While damage to the roofing system itself will more than likely occur in this type of scenario, it is only considered a failure if there is interior surface damage or deflection. Again, this puts a significant requirement on the structural deck that is used. 

Looking at the big picture, this code has put a significant cost burden on affected building owners. It can be expensive to implement the structural modifications required on an existing building. As a result, it has become common for only new construction portions of a building to meet this requirement, especially in schools.

From a roofing perspective, we need to be diligent in our attention to project drawings and specifications. This includes any addendum to the specifications associated with projects that may have a high occupancy or emergency service buildings. And remember, if you run into this (or any) specialty code that has an impact on the roofing system, Duro-Last® Engineering Services can help guide you with a wind calculation to meet the required uplift ratings.