This provision does not require a podium level separation but does require a 1½-hour fire-rated first elevated floor system. It presents a rare opportunity for a nine-story, 100-foot-tall, Type II-A building when there is at least a 50-foot lot line separation. The third provision, Section 510.6, governs Group R-1 and R-2 buildings of Type II-A construction. Figure 1 shows an example of a concrete podium for retail use below a multi-story cold-formed steel framed residential upper structure.įigure 2. For example, by using the residential occupancy and cold-formed steel framing over the top of retail space, one could get the maximum stories of floors and still be under the overall building height limitations when coupled with a multi-story podium. These heights are associated primarily with Type IIA and IB, which require one-hour and two-hour fire-rated assemblies, respectively. For cold-formed steel, there are various UL assemblies as outlined in A Guide to Fire and Acoustic Data for Cold-Formed Steel Floor, Wall and Roof Assemblies ( The most common range for mid-rise non-combustible building materials is five to twelve stories and 85 feet to 180 feet. This is achieved by providing a fire protection system for the bearing walls that meets an hourly rating between one and three hours. For example, residential occupancy classification ranges from five stories to unlimited stories and heights ranging from 75 feet to unlimited heights for non-combustible materials in these construction types. However, with each increase in fire protection, the building is allowed to be taller and have a greater number of stories. Starting with the last point, Type IA, IB, IIA and IIB types of construction require non-combustible materials within a fire-rated assembly, except for IIB which does not have a minimum fire rating for the non-combustible material.
There are three sections in IBC 2015 Chapter Five pertaining to podium designs that describe permissible building heights and story limits and are critical to understand when designing cold-formed steel upper structures over a concrete podium to maximize the benefits of non-combustible steel construction.
The International Building Code (IBC) requires the upper and lower structures to be separated for fire and other safety reasons. Cold-formed steel provides an ideal solution for all of these design challenges. Building height limits also affect building material selection, the treatment of fire safety, sound considerations, architectural unit space planning, and egress. Combining non-combustible materials such as cold-formed steel with concrete and hot-rolled steel results in higher building heights for these structures at an economical price. With this increased density comes the need to provide a safe, non-combustible framing system that is also strong to achieve the desired overall building height. This upper structure lends itself well to individually framed walls and floor systems. The base structure is generally used for parking or retail space, with an upper structure that is of another use, such as apartments, dorms, senior living, hotels or other private spaces. The most common scenario is a base structure, commonly referred to as the podium. Building designers are often challenged with an increasing demand for high-density, combined-use buildings in urban locations.