Fire Resistive (ISO Class 6, IBC Type IA)
Fire Resistive construction is ISO Class 6. ISO Class 6 encompasses IBC Type IA.
- Learn the elements of Fire Resistive Construction. The exterior bearing walls and load-bearing portions of exterior walls must be of noncombustible materials or of masonry, but exterior nonbearing walls and wall panels may be slow burning, combustible, or with no fire-resistance rating.
- Walls:
- solid masonry, including reinforced concrete not less than four inches thick
- hollow masonry not less than 12 inches thick
- hollow masonry less than 12 inches thick, but not less than eight inches thick with a listed fire-resistance rating of not less than two hours
- assemblies with not less than a two-hour fire-resistance rating
- Floors and roofs:
- reinforced concrete not less than four inches thick
- assemblies with not less than a two-hour fire-resistance rating
- Structural metal supports:
- Horizontal and vertical load-bearing protected metal supports — including pre stressed and post tensioned concrete units — with not less than a two-hour fire-resistance rating
- Walls:
Pre- and Post tensioned Concrete
Both pre- and post tensioned concrete units have steel cables installed in the concrete to provide tensile strength. With pre stressed concrete units, builders pull the cables tight before pouring the concrete and release them as the concrete cures. With post tensioned concrete units, builders pull one end of the cable tight after pouring the concrete.
- Note the fire resistive advantages:
- uses noncombustible materials
- allows greater height and area than other construction classes
- uses load-bearing members or assemblies that resist damage from fire
- Note that fire-resistive construction has these disadvantages:
- expensive to construct and repair
- provides a false sense of security