Making defensible space and understanding the “Home Ignition Zone”

Lets use this as the starting point. This is a basic overview and bullet heavy, concept-based article. Understanding the Home Ignition Zone is very important for property owners who live near the forest boundaries or within it. Understanding and then implementing these techniques can keep your home safe against the threat of wild fire.

The Home Ignition Zone, as displayed below, was coined by retired Forest Service Fire Analyst Jack Cohen in the late 1990s. This came about as new research into radiant heat conduction was surfacing.

This sketch displays a clear depiction of our focus on defensible space as it pertains to your home and the “extended” zone. A lot of us in Montana have much larger ignition zones

Moving forward with this concept in mind we want to start understanding big picture what can be done and why, when preparing for this kind of natural or man-made disaster.

An Overview in detail of “The Home Ignition Zone” Prepared by the NFPA. All credit for the next portion is due to the NFPA.

 

Immediate zone

The home and the area 0-5’ from the furthest attached exterior point of the home; defined as a non-combustible area. Science tells us this is the most important zone to take immediate action on as it is the most vulnerable to embers. START WITH THE HOUSE ITSELF then move into the landscaping section of the Immediate Zone.

  • Clean roofs and gutters of dead leaves, debris and pine needles that could catch embers.

  • Replace or repair any loose or missing shingles or roof tiles to prevent ember penetration.

  • Reduce embers that could pass through vents in the eaves by installing 1/8 inch metal mesh screening.

  • Clean debris from exterior attic vents and install 1/8 inch metal mesh screening to reduce embers.

  • Repair or replace damaged or loose window screens and any broken windows Screen or box-in areas below patios and decks with wire mesh to prevent debris and combustible materials from accumulating.

  • Move any flammable material away from wall exteriors – mulch, flammable plants, leaves and needles, firewood piles – anything that can burn. Remove anything stored underneath decks or porches.

Intermediate zone

5-30’ from the furthest exterior point of the home. Landscaping/hardscaping- employing careful landscaping or creating breaks that can help influence and decrease fire behavior

  • Clear vegetation from under large stationary propane tanks.

  • Create fuel breaks with driveways, walkways/paths, patios, and decks.

  • Keep lawns and native grasses mowed to a height of four inches.

  • Remove ladder fuels (vegetation under trees) so a surface fire cannot reach the crowns. Prune trees up to six to ten feet from the ground; for shorter trees do not exceed 1/3 of the overall tree height.

  • Space trees to have a minimum of eighteen feet between crowns with the distance increasing with the percentage of slope.

  • Tree placement should be planned to ensure the mature canopy is no closer than ten feet to the edge of the structure.

  • Tree and shrubs in this zone should be limited to small clusters of a few each to break up the continuity of the vegetation across the landscape.

Extended zone

30-100 feet, out to 200 feet. Landscaping – the goal here is not to eliminate fire but to interrupt fire’s path and keep flames smaller and on the ground.

  • Dispose of heavy accumulations of ground litter/debris.

  • Remove dead plant and tree material.

  • Remove small conifers growing between mature trees.

  • Remove vegetation adjacent to storage sheds or other outbuildings within this area.

  • Trees 30 to 60 feet from the home should have at least 12 feet between canopy tops.

  • Trees 60 to 100 feet from the home should have at least 6 feet between the canopy tops.