The general surroundings of your home and any detached buildings can have a major impact on vulnerability to wildfire. The first step to take is to contact your local fire station get their help in identifying problems in both your neighborhood and on your parcel. See other parts of this Guide for issues related to your structure as well as the “home zone,” the area within 6 feet of the building.
As a rule of thumb, you need to make sure that a fire moving toward your home cannot follow a continuous path through vegetation. In other words, make sure that the plants are small and are in broken clusters (a mosaic arrangement). The closer to the home, the smaller the plants and clusters should be. Also, make sure that ignition of brush will not cause trees to burn. In general, trees are less of a hazard than brush in moving the fire. The main concern with trees is any within a 30-foot area that might release a great amount of heat toward a vulnerable part of your home. Also, certain types of trees (such as pines and eucalypts) generate many burning embers that could threaten your (or your neighbors’ homes). The distances recommended for vegetation management under “slopes” provides a general guidance, but homeowners in a neighborhood should seek the advice of a professional on how to both implement and manage the vegetation over time.
General parcel characteristics
Slope. The critical slope of concern is about 10 to 20 degrees; less than 10 degrees can be thought of as flat. Using a simple protractor, you can determine your slope. Grades over 20 degrees are considered very hazardous. The amount of recommended vegetation management depends largely on the slope:
0 to 10 degrees: 30 feet
10 to 20 degrees: 30 to 60 feet (3 feet per degree)
Over 20 degrees: multiply the number of degrees by 3 to get the distance in feet.
Position of home. If your home is at the top of or somewhere on a slope greater than 10 degrees, you need to double the recommended vegetation management distance. However, if the home is set back from the slope by about 30 feet, then most of the vegetation management can be concentrated in that 30-foot area and about 30 feet down the slope.
Another factor to consider is the most likely direction of winds during fire weather and the aspect of the slope. The worse case scenario is a south-facing slope with winds that would come from that direction. For recommendations of additional vegetation management to account for winds and slope, seek the advice of your local fire authorities.
Distance to closest wooden structure (including fences). If another major structure is within 10 feet of your home, it poses a severe threat from heat released or even burning embers. The implications of this are that you should not have combustible materials on or near that side of your home. This includes siding on the home, fences, firewood, etc. See the section on Fences for guidance on construction and materials. Over about 50 feet of separation, the nearest structure is largely a threat from burning embers. For example, a gazebo with wooden shakes or shingles, or other lightweight wood construction should be modified to eliminate this problem. The 10 to 30 foot spacing is a gray area. Wind-aided flames could easily span this distance with the right wind direction.
Access for equipment. There are two parts to this. One is that you must have enough space for firefighting equipment to move onto your lot, as close as possible to your home (check with fire authorities about this), and to be able to turn around. Next, what is the access to your parcel? The recommended conditions for access are the following:
Two or more roads in and out. Dead-end should have a turnaround as approved by the local fire authority.
An “all-weather” road at least 20 feet wide.
Road grade of less than 5% (5 foot rise for each 100-foot distance).
If you lack any of these, there could be little that you can do as an individual homeowner, but it might be possible to get the neighborhood together to lobby for changes as recommended by your local fire authority.
Water supply. This is another item that you need to discuss with your local fire authority. They can determine the availability of pressurized and non-pressurized water within the distance.