CO-Horts Blog

Tuesday, February 4, 2020

Removing Forest Fuels Now for Defensible Space Later

Posted by Mark J. Platten, Teller County Extension Director

As my cohort, Sherie Caffey, spoke about in a recent blog article, now is a good time for pruning and trimming trees for most species. This is especially true if you are one of the many Coloradans who live in the wildland-urban interface (WUI – pronounced woo-eee). The WUI is any area where structures and other human developments meet or intermingle with wildland vegetative fuels. In many vegetation types, it is not a matter of if a wildfire will impact your home, but when.

Forest Fire photo by Skeeze

Defensible Space

For those of you who live in this zone, you’ve probably heard the term “defensible space” thrown around at an emergency management meeting or even a training put on by the various fire departments or natural resource agencies across the state. A misnomer is that if a homeowner creates a defensible space around their property, it will survive a wildfire. In truth, when fires like the 2002 Hayman, 2012 Waldo Canyon, or 2013 Black Forest fires occurred in my area, they were so massive, with winds pushing embers more than a half mile from the fire front, that it is not fair to say any home in the direct path of those fires were “defensible,” not if we value human life over our homes.
The key is to reduce fire intensity as wildfire nears the house. This can be accomplished by reducing the amount of accomplished by the amount of flammable vegetation surrounding a home. Consequently, the most important person in protecting a house from wildfire is not a firefighter, but the property owner. The action taken by the owner before the wildfire occurs (such as proper landscaping) is the most critical and is why we’re talking about this topic in winter.
Photo by Skeeze
The term does mean is that we can give ourselves a better shot at having our home survive a wildfire and if it is safe for the firefighters to get their vehicles in and back out of your property, they may be able to help protect your structures. If enough of your neighbors, communities, and local/state/federal lands around you are mitigated in a defensible space format, it will likely help slow a wildfire’s advance.
So, while you’re sitting at home because of the recent winter storm (at least that’s what I’m doing) you may want to think about the following steps in providing defensible space around your home and some additional steps in making sure your home isn’t a tinderbox for embers.

Defensible Space Zones

Zone 1

The width of Zone 1 extends a minimum distance of 15-30 feet outward from a structure, depending on property size. Most flammable vegetation is removed in this zone, with the possible exception of a few low-growing shrubs or fire-resistant plants. Avoid landscaping with common ground junipers, which are highly flammable.


Zone 2
Defensible Space Diagram

An area of fuels reduction designed to diminish the intensity of a fire approaching your home. The width of Zone 2 depends on the slope of the ground where the structure is built. Typically, the defensible space in Zone 2 should extend at least 100 feet from all structures. If this distance stretches beyond your property lines, try to work with the adjoining property owners to complete an appropriate defensible space.


Zone 3

Has no specified width. It should provide a gradual transition from Zone 2 to areas farther from the home that have other forest management objectives. Your local Colorado State Forest Service forester can help you with this zone. This zone provides an opportunity for you to improve the health of the forest through proper management.

The Home Ignition Zone

Two factors have emerged as the primary determinants of a home’s ability to survive a wildfire – the quality of the defensible space and a structure’s ignitability. Together, these two factors create a concept called the Home Ignition Zone (HIZ), which includes the structure and the space immediately surrounding the structure. To protect a home from wildfire, the primary goal is to reduce or eliminate fuels and ignition sources within the HIZ.



The roof has a significant impact on a structure’s ignitability because of its extensive surface area. When your roof needs significant repairs or replacement, use only fire-resistant roofing materials. Also, check with your county building department – some counties now have restrictions against using wood shingles for roof replacement or require specific classifications of roofing material. Wood and shake-shingle roofs are discouraged because they are highly flammable and are prohibited in some areas of the state. Asphalt shingles, metal sheets and shingles, tile, clay tile, concrete and slate shingles are all recommended roofing materials.


Roof Eave and Soffits

Soffit Example
The extension of the roof beyond the exterior structure wall is the eave. This architectural feature is
particularly prone to ignition. As fire approaches the building, the exterior wall deflects hot air and gasses up into the eave which is usually cased in a soffit. If the exterior wall isn’t ignition-resistant, this effect is amplified.
The soffit is the skin that covers your eaves — without it, you would see your rafter beams fully exposed. Functionally speaking, soffit protects your rafters from the weather elements. Also, soffit helps your building breathe.  With vented soffit, air can flow through the vents to provide regular air circulation to your attic. This venting is where the embers can be carried into the attic and burn the home from the inside out. You’ll want to make sure your soffits are rated for the heat a wildfire could bring and that any vents are covered with 1/16 steel mesh to prevent embers from being pulled into your home.



Home burning photo by Mark Thiessen
Most decks are highly combustible. Their shape traps hot gasses, making them the ultimate heat traps. Conventional wooden decks are so combustible that when a wildfire approaches, the deck often ignites before the fire reaches the house. This mostly happens because the decks are open beneath and dried leaves, twigs, grass, and other tinder items are contained there so when an ember gets blown under the deck, it combusts. Again, 1/16 metal screening placed around your deck after you clean out all the debris, woodrats, skunks, cats, and neighborhood children, is the best protection from embers.



Windows are one of the weakest parts of a building with regard to wildfire. They usually fail before the building ignites, providing a direct path for flames and airborne embers to reach the building’s interior. Don’t plant shrubs directly below your windows or they could contribute to the windows failing.


Gutters/Chimney/Dryer vents/Stucco gaps

Photo by KRCR News
All these areas are where embers can either ignite or be brought into your home.  Make sure your gutters are clean and even better would be to install gutter guards to prevent buildup of needles, leaves and other debris. The chimney should have an ember arrester on it to prevent you from starting   Finally, a vigilant homeowner who has taken to the steps to build a stucco home for fire protection will want to seal the gap on the outside bottom of the home where the stucco often ends just before meeting the ground. There is a gap of ½-1 inch that is often filled with steel wool to prevent mice from getting in but guess what happens when embers meet steel wool…fire.
a forest fire. An often overlooked item is your dryer vent that could be a vector for embers.
Photo by Mark J. Platten
So, while you’re watching the snowflakes swirl around you, take a break and head outside to do an
inventory of possible issues on both your landscape and home. Then make sure to mitigate those issues to help your home survive the next wildfire.

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