Wildfire Preparedness: Creating Defensible Space

In areas susceptible to wildfires, it’s essential to take all the possible precautions to mitigate the risks associated with this natural disaster. Apart from educating oneself on the forest fire warning signs and developing an evacuation plan, another fundamental wildfire preparedness measure is creating defensible space. This guide will explain what it entails and walk you through the process of ensuring your property is well-protected from wildfire.

What Is a Defensible Space?

Firefighters protecting a house from wildfire

Defensible space, alongside home hardening, is an effective measure undertaken to improve a property’s chances of surviving a wildfire. Essentially, it means creating a vegetation buffer on the land surrounding the building to slow down or prevent the spread of fire. It also implies minimizing the presence of flammable materials on the territory.

However, proper defensible space not only makes the building itself more protected but also provides the firefighters with a safer environment to work in and defend the property from the flames in the event of an emergency.

Where Are the Defensible Space Guidelines Applicable?

While every property could potentially benefit from being organized according to the defensible space principles, there are certain areas that should pay special attention to them. 

Below are the states with the highest number of properties at wildfire risk as of October 2021:

  1. California 
  2. Texas
  3. Colorado
  4. Arizona
  5. Idaho
  6. Washington
  7. Oklahoma
  8. Oregon
  9. Montana
  10. Utah

Keep in mind that the area where your property is located may be subject to location-specific regulations. Thus, it’s always best to consult your local authorities regarding wildfire safety.

However, there are also general defensible space guidelines - read ahead to find out what they are and how to apply them to your property.

Home Ignition Zones

Scheme of home ignition zones

Home ignition zones were developed by a former USDA Forest Service fire scientist Jack Cohen in the late 1990s. The HIZ is a result of experimental research into how buildings ignite due to the effects of radiant heat. 

Nowadays, these zones are typically used as a basis for wildfire defensible space creation.

Immediate Zone

The home itself and its surroundings 0-5 feet from the furthest attached exterior point are the most critical areas of wildfire preparation, as they are extremely vulnerable to embers. Start by preparing the house for potential emergencies and then proceed with the landscaping section of this zone.

Here are the actions you can take to ensure wildfire preparedness of your property’s Immediate Zone:

  • Remove dead leaves, pine needles, and debris from the roofs and gutters.
  • Replace loose or missing shingles or roof tiles.
  • Install 1/8 inch metal mesh screening on the vents.
  • Repair damaged window screens and broken windows.
  • Screen areas below patios and decks with wire mesh.
  • Move any flammable material away from wall exteriors.
  • Clear up the spaces underneath decks and porches. 

Previously, the establishment of this zone wasn’t required by law. However, in California, for instance, the Assembly Bill 3074, passed into law in 2020, requires the Board of Forestry and Fire Protection to develop the regulation for a new ember-resistant zone by January 1, 2023. 

Intermediate Zone

This zone within 5-30 feet from the furthest exterior point of the house plays a significant role in creating a fire defensible space. 

Here are the main guidelines one should follow to maintain the Intermediate Zone protected from wildfire:

  • Clear vegetation from under stationary propane tanks.
  • Create fuel breaks with paths, patios, walkways, and decks.
  • Keep lawns mowed to a height of 4 inches.
  • Remove ladder fuels - live or dead vegetation that enables a fire to climb up from the landscape into the tree canopies.  
  • Space the trees to have a minimum of 18 feet between crowns with the distance increasing along with the percentage of slope.
  • Plan the tree placement so that the mature canopy is no closer than 10 feet to the edge of the building.
  • Break up the continuity of the vegetation in this zone by planting the trees and shrubs in small clusters.

Extended Zone

This is the zone that stretches 30-100 feet away from the house. The goal with the Extended Zone is to interrupt the flames’ path and keep them close to the ground.

Here’s how to do it:

  • Get rid of litter and debris accumulated on the ground.
  • Dispose of all the dead plants and trees.
  • Clear up the small conifers that grow between mature trees.
  • Remove any vegetation next to storage sheds or other structures.
  • The trees growing 30 to 60 feet from the house must have at least 12 feet between the canopy tops.
  • The trees growing 60 to 100 feet from the house must have at least 6 feet between the canopy tops.

Additional Tips on Creating Defensible Space

A road between the land affected by wildfire and untouched greenery

With the knowledge of home ignition zones, you have a solid basis for creating defensible space for your house. However, the final plan regarding the landscaping, hardscaping, and cleanup steps you should take will depend on your property and its location.

Here are some additional focal points to consider:

  • During the periods when the vegetation is full-leaved, check whether it prevents the house number from being visible. If it does, perform trimming accordingly.
  • Ensure that you throw away charcoal briquettes and fireplace ashes only after soaking them in a metal bucket with water for many hours.
  • If your property has a swimming pool or well, invest in a portable water pump that could be used to fight fire in the event of an emergency.
  • Consider installing sprinklers on the roof to douse embers before a fire can ignite.

Creating defensible space is a process that requires a holistic approach, from house construction and landscaping to cleanup and property maintenance. With the tips listed in this guide, you are sure to minimize the danger imposed by wildfires even in the most high-risk areas.