Fire Resistive Construction

Construction Class 6

Overview

This Construction Brief will give you an overview of Verisk's Construction Class 6 – fire-resistive fire-resistive-construction 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