Joisted Masonry Construction

Construction Class 2

Overview

This Construction Brief will give you an overview of Verisk Construction Class 2 – joisted masonry joisted-masonry construction. When you've completed this course, you will know what a Verisk report means when it says a building is joisted masonry construction. And you will understand why a particular structure is—or isn't—joisted masonry.

Definition

Buildings with exterior walls of masonry or fire-resistive construction rated for not less than one hour and with combustible floors and roofs.

Types of joisted masonry

There are several types of masonry used in the exterior bearing walls of joisted masonry buildings:

Brick
Concrete—either reinforced or nonreinforced
Hollow concrete masonry units
Tile
Stone

Exterior bearing walls may also be any noncombustible materials with fire-resistance ratings of not less than one hour.

Variation of joisted masonry construction

There's one variation on joisted masonry construction that doesn't change the construction class— variation-of-joisted-masonry heavy timber or mill construction.

Heavy timber construction uses wood members much larger than those found in frame (Construction Class 1) or other joisted masonry construction.

If the building uses steel columns or beams for walls, the beams must be protected so they have a fire-resistance rating of not less than one hour.

Heavy timber construction

Verisk classifies the building as heavy timber construction if it meets these requirements:

Walls of masonry construction
Floors of three-inch wood plank or four-inch laminated plank, both surfaced with one-inch flooring
Roof of two-inch wood plank, three-inch laminated plank, or 1-1/8 inch tongue-and-groove plywood deck
Wood column supports not less than eight-inch x eight-inch, wood beams or girders not less than six-inch x six-inch, or protected metal

Heavy timber advantages

Heavy timber construction offers these advantages:

Harder to ignite
Consumed more slowly by fire
More structural stability
Greater salvage value
Lack of concealed spaces

Joisted masonry disadvantages

Joisted masonry construction has these disadvantages:

Floors and roofs of combustible materials subject to damage by fire
Presence of concealed spaces