This Construction Brief will give you an overview of ISO's Construction Class 5 – modified fire resistive construction. When you've completed this course, you'll know what an ISO report means when it says a building is modified fire resistive construction. And you'll understand why a particular structure is—or isn't—modified fire resistive.
- Buildings with exterior walls, floors, and roofs of masonry materials described in the definition of fire resistive (Construction Class 6)—less thick than required for fire-resistive structures but not less than four inches thick, or
- Fire-resistive materials with a fire-resistance rating less than two hours but not less than one hour
Wall, floor, and roof assembly with noncombustible panels, with one-hour fire-resistance rating
Poured gypsum roof with one-hour fire-resistance rating
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.
Metal lath and plaster
Here are examples of metal lath and plaster applied to steel
Metal lath and plaster protects the beam.
Here are examples of sprayed-on materials applied to steel:
Here is an example of gypsum board applied to steel:
Advantages of fire-resistive construction
- Uses noncombustible materials
- Allows greater height and area than other construction classes
- Uses load-bearing members or assemblies that resist damage from fire