Fire Safety at the Wildland/Urban Interface
By landscaping your home to minimize highly flammable materials in the area near it you can provide the equivalent of a firefighters fire break. You can do this with non-flammable materials such as stone mulch, patios, etc., but you can also do this by carefully selecting and arranging your plantings. This concept is termed Defensible Space. It depends on some simple ideas to make your Defensible Space less flammable:
The Concepts for FireWise Defensible Space:
•Maintain a 30-100 feet wide safety zone around structures – use the Zone concept
•Minimize the amount of "fuel"
•Eliminate the opportunity for flames to come in direct contact with homes or other structures
•Prevent plant-to-plant spread of fire
•Use fire-resistant mulches and ground covers like those mentioned in Table 7.1
Use fire resistant plants like those mentioned later in the chapter
Maintain a Safety Zone Around Structures
The key to maintaining a Defensible Space is to maintain a zone around the house and other structures that is very fire resistant. The size of this area is variable. Experts advise between 30 and 100 feet of buffer. A number of factors should go into your decision as to how much space to allow.
Part of your Defensible Space decision is based on what you are able to do given your property size. You can’t clear wildlands, forestry lands, or national parks at all, and you can’t clear your neighbors’ properties without some kind of agreement with them. We will discuss how you can work with your neighbors later in the section about FireWise Communities. If you live near a pine plantation or are surrounded by mountain laurel, you should allow as much space as possible. If, on the other hand, your area has less intense fires, you can get by with less of a Defensible Space. A way to think about this is if you live in a deciduous forest, 30 feet could be an adequate buffer, while in a pine forest the buffer should be closer to 75 feet.
Where your house lies in the landscape is another important part of your Defensible Space decision. In hilly terrain, if your home is at the top of a slope, you will need more space on the side of the house facing the slope to counteract how a wildfire can race up a slope. Allow no less than 30 extra feet for the sloped area in addition to the other buffer areas. If you can leave a 100-foot buffer, all the better. If the space you have is limited you could consider terracing the slope to slow fire spread. If the face of the terraces is not flammable such as stone retaining walls, ground fires can be checked, and even more severe fires can be slowed substantially. Additionally you can remove the most flammable species such as juniper, pine, and cedar (see more about plant choices later). If your home is in a wide open space where strong winds might drive a fire towards your house you should allow more space on that side of your house.
How your landscape is planted is the last component of your Defensible Space decision. Below we will talk about FireWise planting choices. If you have a landscape with plants that are more flammable you should arrange more of a buffer between the wildlands where fire could be burning and those flammable plantings.
A good way to tie these concepts together is the "Zone Concept". By thinking of four functional zones around your house you can do a lot to help defend your house from encroaching fire (Figure 7.8).
Figure 7.8: The Zone Concept
Establishing zones in your yard. Illustration by Sarah Lynch-Walker.
Eliminate Opportunities for Fire Spread
Lots of people who live near the Wildland/Urban Interface have decks, fences, and other wooden structures attached to their homes which are in direct contact with the ground. Worse still, these wooden structures have plantings that actually touch the wood. This gives fire a direct connection to your home or other structures on your property. It is best to avoid having plantings that actually touch the house, or to have these plantings isolated from the surrounding landscape by hard structures such as patios or stone pathways.
Prevent Plant-to-Plant Spread of Fire
Obviously plants fuel a fire. Planting them so that there are slower burning buffers between more flammable plantings can help stop the spread of fire towards your house. For example, shrubs or trees in the landscape can be separated from one another by expanses of lawn or non-flammable mulches.
One thing to avoid in the landscape is the tendency to layer plants from lower to higher. This is a classic landscaping technique but it can allow a ground fire to burn first on the ground then to ever higher growing shrubs, trees, and eventually the house; or, it could help a slowly moving ground fire morph into a rapidly burning crown fire. This effect is known as the fire ladder, and stacking your plants like that is what is termed ladder fuels.
Figure 7.9: Types of Fire
Types of wildlands fire and how the Fire Ladder effect allows fires to spread faster.
Illustration by Sarah Lynch-Walker.
In order to minimize the potential for disaster with this type of planting you should consider doing it in such a way as to ensure that the stacked bed is far from the home in a stand-alone bed. Another, less favorable approach is to isolate the beds that are ladder fuels from encroaching fire by having them deep in your landscape and isolated by some type of hardscape: the driveway or stone walkway.
There are other things you can do to help landscape your home in a FireWise manner
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