Creating defensible space is essential to improving your home's chances of surviving a wildfire. Defensible space is the buffer you create between a building on your property and the shrubs, grass, trees, and any wildland area that surround it. Not only does this space slow or stop the spread of wildfire, it can protect your home from catching fire—either from direct flame contact or radiant heat. Defensible space is also important for the protection of the firefighters defending your home.
What are the Zones? Readyforwildfire.org lists them this way:
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.
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
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.
*The distances listed for crown spacing are suggested based on NFPA 1144. However, the crown spacing needed to reduce/prevent crown fire potential could be significantly greater due to slope, the species of trees involved and other site specific conditions. Check with your local forestry professional to get advice on what is appropriate for your property.
Plant and Tree Spacing
The spacing between grass, shrubs, and trees is crucial to reduce the spread of wildfires. The spacing needed is determined by the type and size of brush and trees, as well as the slope of the land. For example, a property on a steep slope with larger vegetation requires greater spacing between trees and shrubs than a level property that has small, sparse vegetation.
Remove all tree branches at least 6 feet from the ground.
Allow extra vertical space between shrubs and trees. Lack of vertical space can allow a fire to move from the ground to the brush to the tree tops like a ladder.
To determine the proper vertical spacing between shrubs and the lowest branches of trees, use this formula:
3 x height of shrub = minimum vertical clearance
Example: A five foot shrub is growing near a tree. 3×5 = 15 feet of clearance needed between the top of the shrub and the lowest tree branch.
Horizontal spacing depends on the slope of the land and the height of the shrubs or trees. Check the chart below to determine spacing distance.
Fire-resistant landscaping isn’t necessarily the same thing as a well-maintained yard. This style of landscaping focuses on the right plants with emphasis on the right placement. Avoid long continuos rows of plants. Don't create ladder affects of vegetation with your landscaping. Especially avoid long rows of plantings that lead directly into contact with your structures or fencing. Spacing plants that are strategically separated to resist the transfer of fire from the trees or ground directly to your home is key.
Consider that wood chips, mulch, and bark are quickly combustible. This is why the NFPA guidelines suggest not having any in the 5 foot zone of your home, buildings or infrastucture. Mulch can still have a place in the overall landscape if you safely plan location and keep the distribution at a thin layer. Before choosing the mulch you purchase this year, take a look at the information on flamability from UNR in this flyer about Mulch.pdf