Defensive Space - Int'l Association of Certified Home Inspectors (InterNACHI)

By Nick Gromicko and Kenton Shepard

When talking about defensive space we mean the area around an attenuated building to protect it from fires. In addition to the quality of a building's roofing material, proper defensive space is one of the most important factors in determining a building's ability to survive a fire. Inspectors should know enough about defensive spaces to educate their customers, particularly in regions that are most prone to fire.

The defensive space fulfills the following functions:

Colorado State University divides defensive spaces into three categories as follows: Zone 1: The first 15 feet should be devoid of any flammable vegetation. Firewood and other flammable materials should not be stored in this area.

Zone 2: This area of ​​fuel reduction should extend from Zone 1 outwards between 75 and 125 feet from the structure. Trees and large shrubs should be no less than 10 feet apart, especially on steep terrain. Also, trees should be pruned at a height of 10 feet from the ground and any "ladder fuel" (vegetation with vertical continuity) removed from the base of the trees. Grass, trees and shrubs in this area should be green and adequately spaced. Pineapples, dead leaves, branches, dead or withered vegetation and any flammable debris on the floor should be removed as soon as it appears.

Zone 3: This area of ​​the traditional forest management system does not has a specific size, although it normally extends to the limits of the property. More trees are allowed than in Zone 2, although maintaining their health and vigor.

In short, buildings can be saved from fire damage by eliminating the surrounding flammable vegetation. The defensive spaces are critical in warm, dry and forested regions, although its presence is recommended everywhere.

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