Defensible Space

Step 1

Locate Your Plan Unit

Step 2

Review Your Resident Action Plan

Creating Defensible Space

Resident Action Plan

Defensible space creates a buffer between your home and grass, trees, and shrubs that could ignite during a wildland fire. Defensible space can slow the spread of wildfire, prevent direct flame contact, reduce the chance that embers will ignite material on or near your home, and give FireFighters room to protect your home.

Do not count on firefighters staying to defend your home! Your home should be able to stand strong on its own during a wildfire.

There are never enough firefighters to stay and defend every single home during large incidents. Properties that are not defensible will often not receive firefighter resources due to unsafe conditions and the higher likelihood of home loss regardless of firefighter intervention.

Substantially reducing vegetation within the Home Ignition Zone and removing vegetation that overhangs decks and roofs can reduce structure loss, especially for homes on slopes. Defensible space is divided into three zones around a home or other structure, and recommended practices vary among zones.

The Colorado State Forest Service (CSFS) defines zone 1 as 0 to 5 feet from the home, zone 2 as 5 to 30 feet from the home, and zone 3 as 30 to 100 feet from the home.

Property owners should establish defensible space around each building on their property, including campers / RVs, detached garages, storage buildings, barns, and other structures. RVs are highly flammable and can emit embers that might ignite nearby homes and vegetation. Removing all vegetation under and around campers in zone 1 is crucial. Campers / RVs, boats, detached garages, storage buildings, barns, and other large structures should be placed at least 50 feet away from primary structures to prevent structure-to-structure fire spread.

A 2021 study from the University of Colorado-Boulder showed that homeowners living in the Wildland-Urban Interface (WUI) in Bailey, CO typically underestimated the level of risk their home is at due to wildfire, and tended to overestimate the amount of work they have done to protect their property. Make sure you are informed about best practices for protecting your home. See Table 3.a.1 and the Colorado State Forest Service publication The Home Ignition Zone for recommendations. Section 3.c includes specific defensible space recommendations by forest type for zone 3.

Zone 1: 0 to 5 feet from your home – the noncombustible zone.

Goal: Prevent flames from coming into direct contact with your home.

Create a noncombustible border 5 feet around your home. Remove all vegetation and replace flammable wood chips or mulch with alternatives like dirt, stone, flagstone, concrete, or gravel. Research shows that the worst materials to use in zone 1 are shredded rubber, pine needles, and shredded western red cedar due to their high flammability (Quarles and Smith, 2011).
Remove branches that hang over your roof and drop needles onto your roof.
Remove all fuels within 10 feet of the chimney.
Remove combustible materials (dry vegetation, wooden picnic tables, juniper shrubs, etc.) from underneath, on top of, or within 5 feet of decks, overhangs, windows, and doors.
Annually remove dead or dry leaves, pine needles, and dead plants within 5 feet of your home and off your deck, roof, and gutters. Raking material farther than 5 feet from structures will not significantly reduce the likelihood of ignition.
Move firewood or other combustible materials to zone 3.
Do not use space under decks for storage.

Zone 2: 5 to 30 Feet From Your Home

The Lean, Clean & Green Zone

Goal: Slow the Movement of Flames Approaching Your Home & Lower the Fire Intensity

Irrigate and mow grasses to 4 inches tall or less. If you are unable to irrigate, replace dry grasses with low-flammability plants that are more drought tolerant and less flammable.
Remove any accumulated surface fuels such as logs, branches, slash, and mulch.
Remove all common junipers because they are highly flammable and tend to hold a layer of flammable material beneath them. Landscape with plants that have more fire-resistant attributes, like short-statures, deciduous leaves, and higher moisture content. See low-flammability plants from Colorado State University Cooperative Extension for suggestions.
Remove enough coniferous trees to create at least 10 feet* of space between crowns. Measure from the outermost branch of one tree to the nearest branch on the next tree. Create even more space between trees if your home is on a slope (Table 3.a.2). See Figure 3.a.4 for how to measure crown spacing.
Favor the retention of aspen trees because this species naturally has high fuel moisture, no low branches, smooth bark, and lower content of resin and other volatile compounds, making them less likely to ignite than conifer trees. Remove only downed or standing dead aspen trees.
Remove ladder fuels under remaining trees. This is any vegetation that can bring fire from the ground up into taller fuels. Keep shrubs at least 10 feet* away from the edge of tree branches.
Remove limbs so branches do not hang below 6 feet above the ground, ideally not below 10 feet above the ground. See Figure 3.a.3 for a depiction of how to measure limb height.
Keep spacing between shrubs at least 2-3 times their height.
Relocate wood piles and propane tanks to zone 3.
Remove stressed, diseased, dead, or dying trees and shrubs. This reduces the amount of vegetation available to burn and improves forest health.

Zone 3: 30 to 100 Feet From Your Home

The Lean, Clean & Green Zone

Goal: Slow the Movement of Flames, Move Fire to the Ground, & Reduce Ember Production

If you live on a slope, zone 3 should be larger due to the greater potential for extreme fire behavior.
Store firewood and propane tanks at least 30 feet away and uphill from your home and away from flammable vegetation. Store even farther away if your home is on a slope.
Move campers / RVs, boats, detached garages, storage buildings, barns, and other large structures at least 50 feet away from your home.
Mow or trim grasses to a maximum height of 6 inches. Grasses can be taller in zone 3 than zone 2 because of the greater distance from your home, but shorter grass is always better for reducing potential flame lengths and therefore radiant heat exposure.
Follow guidance in Section 4.c Recommendations by Vegetation Type to determine the best management practices for the trees and shrubs in your zone 3. This usually involves reducing the number and density of trees and/or altering their arrangement.
Favor the retention of aspen trees because this species naturally has high fuel moisture, no low branches, smooth bark, and lower content of resin and other volatile compounds, making them less likely to ignite than conifer trees. Remove only downed aspen trees.
Remove limbs so branches do not hang below 6 feet above the ground, ideally not below 10 feet above the ground. See Figure 3.a.4 for a depiction of how to measure limb height.
Remove shrubs and saplings that can serve as ladder fuels.
Remove heavy accumulations of dead trees and branches.
Consult with a qualified forester to develop a plan to manage your property to achieve fuel reduction and other goals, such as creating wildlife habitat. Follow principles of ecological restoration as outlined in Section 4.a

Some homeowners in the WUI are concerned that removing trees will destroy the forest and reduce the aesthetic and monetary value of their property. In fact, many dense ponderosa pine forests are unhealthy and greatly diverged from historical conditions that were maintained by frequent wildfires. The reality is that nothing will decrease the aesthetic and monetary value of your home as much as a high-severity wildfire burning all the vegetation in the community, even if your home survives the fire.

Forest management can look messy and destructive in the first years following treatment; however, grasses, shrubs, and wildflowers will respond to increased light availability after tree removal and create beautiful ecosystems with lower fire risk. It might even be said that the more trees you cut, the more trees you save from wildfire.

Many property owners enjoy their land even more after conducting effective fuel treatments. Removing trees can open incredible views of mountains, rivers, and rock formations, and wildlife are often attracted to forests with lower tree densities and a greater abundance of understory plants. Reducing fuel loads and increasing the spacing between trees increases the chance that your home and your neighbors’ homes will stand strong during a wildfire, and most importantly, it increases the safety of wildland firefighters working to protect your community.