– By Charles Praeger – It’s not always easy to check every box on a client’s check list. Some customers need guidance to understand what is feasible, as well as reassurance to validate decisions. For those with safety as the top project priority, a solid solution is to suggest a metal building system. Recent testing validates metal buildings’ characteristics and proves their strength when it comes to fire ratings and performance.
The Necessity
Are fire ratings and fire testing necessary with a metal building system? A metal building system consists of structural steel framing, which is non-combustible. Despite this designation, fire protection is necessary based on the intended use, occupancy and site location of your building. For site location, the International Building Code requires that buildings within five feet of each other or on a property line include a fire wall. The risk of fire spreading from building to building decreases as the distance between buildings increases. Likewise, the fire-resistance rating requirements go down with this lower risk. Additional requirements are set for fire ratings based on the intended end-use of the building and construction type, with differences in requirements for wood, steel or concrete.
Roofing and wall cladding materials also impact a building’s integrity and, therefore, affect performance requirements. This is where selecting additional metal products could benefit a building project. “Just like steel framing, metal roofing and walls have advantages when it comes to fires,” said Brad Robeson, chairman of the Cleveland-based Metal Building Manufacturers Association. “Metal panels are not flammable or combustible. However, you need to review fire ratings with a manufacturer because ratings do vary among metal roofs and wall products based on testing. Manufacturers need to submit their products for UL (Underwriters Laboratories) testing to officially achieve Class A, B or C fire rating for an individual product though most metal products achieve Class A.” Metal building roofs are considered by the code to be Class A without required testing if the roof is installed on non-combustible open framing, such as metal roof purlins.
If you have a building with occupied spaces, then size limitations and safety come into play for your plans; IBC sets size and height limitations if a space is unprotected. Using fire-resistance rated construction materials or sprinklers allow a building’s size and height to increase. This begins with passive materials, which can include gypsum wallboard; concrete masonry for walls; or spray-applied fire protection. A commonly used material for fire-rated designs is 5/8-inch Type X gypsum board. The requirements for thickness and number of layers, supports, screw spacing and any other features will vary from project to project. For instance, intumescing fire caulks are sometimes needed to help seal any gaps or cracks. This prevents the passage of smoke and flames.
Customization options continue from the inside out with the freedom to create open spaces. “Metal buildings do not have to be boring, box-like structures,” Robeson noted. “A metal building system structure allows interior spaces to be configured—and reconfigured—to meet a building owner’s needs. Cladding materials, which can be anything from metal to brick, stone, EIFS, glass and more, allow a building to reflect its purpose and design while being a code-compliant structure.”
Testing
These and other fire rating requirements came from testing that occurred at UL, Omega Point Laboratories (now Intertek) and Factory Mutual. Because of this, the industry now has ceiling, wall and column protection details that are UL listed assemblies. A recent MBMA sponsored test is UL Design No. W404, a 1-hour rated fire wall that allows for new and retrofit metal building use and provides the flexibility to meet future energy code requirements for higher insulation levels. The 2-hour version of this new fire wall is known as UL Design No. W413. This provision has some additional components that extend the rating, and fiberglass and rigid board insulation are both allowed with these ratings. This is important when considering energy efficiency because it allows future energy codes, with anticipated higher standards, to be taken into consideration for material selection. The fire test for both these ratings was set to pass at the maximum spacing. Therefore, girts can be spaced as far apart as 7-1/2 feet, so the design is useful for both new and retrofit construction.
While every building may not require fire protection because of its location or occupancy designation, codes and standards requirements always must be met for a particular project. Constructing with a metal building system can bring a sense of safety to your customers, and recent testing helps increase that trust.
Charles Praeger is the assistant general manager of the Metal Building Manufacturers Association, Cleveland, Ohio, and past chairman of the Cool Metal Roofing Coalition.