DEFENSIBLE SPACE FAQ: PNWCG

FREQUENTLY ASKED QUESTIONS ABOUT DEFENSIBLE SPACE:

In the 1980s, the term "defensible space" was coined to describe vegetation management practices aimed at reducing the wildfire threat to homes.

WHAT IS DEFENSIBLE SPACE?

The area between a home and an oncoming wildfire where the vegetation has been modified to reduce the wildfire threat -- and to allow firefighters to effectively defend the house -- is called defensible space. Sometimes a defensible space is simply a homeowner's properly maintained backyard.

WHAT IS THE RELATIONSHIP BETWEEN VEGETATION AND WILDFIRE THREAT?

helicopter photo by Ben Hammack Many people do not consider the plants growing on their property a threat. But in terms of wildfire, the vegetation adjacent to their homes can have considerable influence on the survivability of their homes. All vegetation, including plants native to the area as well as ornamental plants, is potential wildfire fuel. If vegetation is properly modified and maintained, a wildfire can be slowed, the length of flames shortened, and the amount of heat reduced, all of which helps firefighters defend the home from an oncoming wildfire.

THE FIRE DEPARTMENT IS SUPPOSED TO PROTECT MY HOUSE, SO WHY BOTHER?

Some people incorrectly assume that a fire engine will be parked in their driveway and firefighters will be actively defending their home if a wildfire approaches. During a major wildfire, it is unlikely there will be enough firefighting resources available to defend every home. In these instances, firefighters will likely select homes they can most safely and effectively protect. Even with adequate resources, some wildfires are so intense that there is little firefighters can do to save a home from burning. The key is to reduce fire intensity as the wildfire nears the home. This can be accomplished by reducing the amount of flammable vegetation surrounding a home. Consequently, the most important person in protecting a home from wildfire is not a firefighter, but the property owner. And it's the action taken by the owner before the wildfire occurs (such as proper landscaping) that is most critical.

fire photo by Dave Hill DOES DEFENSIBLE SPACE REQUIRE A LOT OF BARE GROUND IN MY LANDSCAPE?

No. Unfortunately, many people have this misconception. While bare ground is certainly effective in reducing the wildfire threat, it is unnecessary and unacceptable -- due to appearance, soil erosion, and other reasons. Many homes have attractive, well vegetated landscapes that also serve as effective defensible space.

DOES CREATING A DEFENSIBLE SPACE REQUIRE ANY SPECIAL SKILLS OR EQUIPMENT?

No. For the most part, creating a defensible space requires just routine gardening and landscape maintenance practices such as pruning, mowing, weeding, plant removal, appropriate plant selection, and irrigation. Equipment needed includes common tools such as a chain saw, pruning saw, pruning shears, loppers, weed-eater, shovel, and a rake. A chipper, compost bin, or a large rented trash dumpster may be useful in disposing of unwanted plant material.

HOW BIG IS AN EFFECTIVE DEFENSIBLE SPACE?

Defensible space size is not the same for everyone, but varies by slope and type of vegetation growing near the home. See the section called "Creating An Effective Defensible Space" for details.

DOES DEFENSIBLE SPACE MAKE A DIFFERENCE?

Yes. Investigations of homes threatened by wildfire indicate that those with an effective defensible space are much more likely to survive a wildfire. Furthermore, homes with both an effective defensible space and a nonflammable roof (composition shingles, tile, metal, etc.) are many times more likely to survive a wildfire than those that have defensible space and flammable roofs (wood shakes or shingles). These conditions greatly influence firefighters' ability to effectively and safely defend the home.

DOES HAVING A DEFENSIBLE SPACE GUARANTEE MY HOME WILL SURVIVE?

No. Under extreme conditions, almost any home can burn. But having a defensible space will significantly improve the odds of your home's survival.

WHY DOESN'T EVERYONE LIVING IN A WILDFIRE HAZARD AREA CREATE A DEFENSIBLE SPACE?

Reasons for not creating a defensible space are varied. Some people believe "it won't happen to me." Others think the costs (time, money, effort, loss of privacy, etc.) outweigh the benefits. Some fail to implement defensible space practices simply because of lack of knowledge -- or misconceptions about the issues.

HOW DO I CHANGE VEGETATION ON MY PROPERTY TO REDUCE WILDFIRE THREAT?

The objective of defensible space is to reduce the wildfire threat to a home by changing the characteristics of the adjacent vegetation. Defensible space practices include:

increasing the moisture content of vegetation
decreasing the amount of flammable vegetation
shortening plant height
altering the arrangement of plants

This can be accomplished through the "Three R's of Defensible Space." The section called "Creating An Effective Defensible Space"provides detailed information about changing vegetation characteristics for defensible space.