Overview
This Construction Brief will give you an overview of Verisk's Construction Class 6 – fire-resistive
construction. When you've completed this course, you will know what a Verisk report means when it says a building is fire-resistive construction. And you'll understand why a particular structure is—or isn't—fire-resistive.
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 prestressed and posttensioned concrete units—with not less than a two-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.
Pre- and post-tensioned concrete units
- 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.
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
Disadvantages of fire resistive construction
- Expensive to construct and repair,
provides a false sense of security