Firewise Homes

Fire! It is a reality for those living in Idaho’s wildland urban interface landscape. A natural part of the forest and rangeland ecosystems of Idaho, fire is an important element of healthy ecosystems. Idaho’s many environments offer beauty and recreation to those fortunate to live or vacation here. But along with the many benefits we reap from living and playing in the wildland urban interface, we also have increased risks and responsibilities.

When wildlife destroys homes and threatens lives, this natural agent of renewal becomes an agent of disaster. As a homeowner, the following pages include things you should know and can do to ensure that living and playing in the WUI continues to reaps benefits and not disasters.

Home Ignition

Many people believe that wildfires ignite homes by the direct contact
of flames on flammable surfaces. But it is rare to have a home ignite
this way. More commonly, homes ignite either by being preheated by an
approaching wildfire to the point of combustion, or more commonly, from
air-borne flaming brands and embers commonly called “red snow”. Flaming
brands and embers can travel as far as 5 miles ahead of the active front
of a wildfire and recent research has shown that up to 60% of
wildland/urban interface home ignitions are from “red snow” landing on
flammable roofs or in other flammable objects, which in turn ignites the

Homes that are not vulnerable to ignition will likely not burn in a  wildfire. Most of the activity that makes a home less vulnerable to  ignition addresses the home and it’s immediately surroundings out to 100  feet. There are many things you can do to decrease your home ignition  potential, many of which costs little money and can be done in a weekend. Firewise Building  Materials  includes information about non-flammable building materials,  suggestions for new home construction, building codes and ordinances,  and how to retrofit your existing home to make it less flammable. Firewise Landscaping  includes information on how to design, install, and maintain a firewise  landscape, descriptions on what makes a particular plant more  fire-prone than another, and a short-list of some firewise plant  material ideas for Idaho.

Defensible Space

Adjacent defensible spaces overlap to provide added protection.

The defensible space of a firewise landscape is divided into three treatment zones, which increase in fire resistance as you get closer to your home and structures. A minimum treatment area of 100 feet is recommended for homes and outbuildings on flat ground, and up to 200 feet or more on sloped sites. This is because fire behaves differently on slopes and in draws than it does on flat areas. For more information on fire behavior go to the Science of Fire section.

Your defensible space is the area that includes your home and its immediate surroundings, and is where you have made a concentrated effort to reduce the chance of an ignition by wildfire or flaming embers. Defensible space starts with your home and moves out into the landscape from there. In areas with homes that are close enough to each other, defensible spaces may overlap to provide added protection for the subdivision.

Zone 1. Your Home (the red zone)

In zone 1, steps have been taken to decrease and/or eliminate the ignition potential of your home. Particular attention is paid to non-flammable roofing, enclosing soffits and overhangs, removing debris from roofs and gutters, and identifying flammable items such as patio furniture, brooms, flowerboxes, doormats, etc. For more information on how to make your home more fire resistant go to the Firewise Building Materials section.

Zone 2. Your landscape (the yellow zone)

In zone 2, the home is surrounded by a greenbelt of well-watered and maintained plant materials. Perennials, ground-covers, and annuals are planted in groups with individual trees and shrubs. These islands of vegetation are surrounded by rock or brick retaining walls and well-watered turf. Firewood and propane tanks are placed on gravel or concrete pads. This zone requires yearly removal of overgrowth and dry debris on the ground, as well as pruning trees.

Zone 3. Beyond 100 feet (the green zone)

Zone 3 is composed of native vegetation that has been thinned. If possible, highly flammable species of trees and shrubs are removed and replaced with less-fire-prone species.