BY DANNY STRATTON

A fire originating below the first floor of a residential structure is very vulnerable. It is important that fire control measures are executed to stop the extension of combustion, which can overtake occupants and the structure more readily than a fire in any other location. We, the suppression specialists, must take aggressive action to save the entire structure from a fiery destruction and execute life-saving measures to make a safe environment in all areas of the building.

Concerns associated with a fire below the first floor (as opposed to one in any other compartment of the structure such as a top-floor bedroom fire) include fire spreading through the attic space and damage to the structural elements of the roof that has little or no load imposed on it. In the division below the first floor, the fire problem is amplified. The entire structure and its occupants on all levels are in the path of dangerous by-products of combustion, and there are heavy floor loads that can release on failure.

DEFINING “BELOW GRADE”

What do we have underneath the first or main floor of a residential structure? For the purpose of technical terminology, let’s define the different compartments that can be below the first floor. We need to be familiar with three types: crawl space, basement, and cellar. Each has individual characteristics.

A crawl space is common in ranches, modular type homes, and garden apartments. This space may be in combination with a cellar or a basement in some occupancies. Its purpose is to facilitate air circulation and provide access for repairs such as plumbing, electric, and so on. This tight space is usually at least a foot in height and has a dirt or gravel surface (photo 1).

(1) A structure with a typical crawl space. (Photos by author unless otherwise noted.)

Often, “basement” is the preferred layman’s term used to describe both the basement and the cellar. A basement has more than half of the height of the exterior foundation wall aboveground and standard size windows just like the upper floors . A standard door may also be present, which provides access to the exterior from the basement. This is common in an apartment building.

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