Vegetation management has proven to be a major factor in reducing the probability of buildings igniting from wildfires. When combined with special building construction features and following defensible space guidelines, the potential for ignition is further reduced. Vegetation management involves managing the spacing, height, species, etc., of vegetation around the structure to reduce the risk of a structure fire spreading into the wildland or a wildland fire spreading to a structure.

The intensity of wildfire fuel management varies within the 100-foot perimeter of the building, with more intense fuel reduction occurring closer to the building. Start at the building and work your way out to 100 feet or to your property line, whichever is closer.

Zone 0 – Ember-Resistant Zone:

“Zone 0” refers to the 0–5-foot area surrounding a structure. This area is designed to be an ember-resistant zone, meaning it’s cleared of combustible materials like mulch, vegetation, and wooden fences. The goal is to prevent embers from igniting materials that could then spread fire to the home. Zone 0 includes the area under and around all attached decks and requires the most stringent wildfire fuel reduction. The ember-resistant zone is designed to keep fire or embers from igniting materials that can spread the fire to the building

·        The following guidance may change based on regulations developed by the Board of Forestry

What to do:

1. Use hardscape like gravel, pavers, or concrete. No combustible bark or mulch.
2. Remove all dead and dying plants, weeds, and debris (leaves, needles, etc.) from your roof, gutter, deck, porch, stairways, and under any areas of your home.
3. Remove all branches within 10 feet of any chimney or stovepipe outlet.
4. Limit combustible items (like outdoor furniture and planters) on top of decks.
5. Relocate firewood and lumber to Zone 2.
6. Replace combustible fencing, gates, and arbors attached to the home with noncombustible alternatives.
7. Consider relocating garbage and recycling containers outside this zone.

Consider relocating boats, RVs, vehicles, and other combustible items outside this zone.

Zone 1 – Lean, Clean and Green Zone

Zone 1 of defensible space, also known as the “Lean, Clean, and Green” zone, extends 30 feet from buildings, structures, decks, or to the property line, whichever is closer. This zone focuses on removing combustible materials and reducing fire pathways to protect structures from wildfires. 

Regularly clear dead or dry vegetation and create space between trees. During times of drought when watering is limited, pay special attention to clearing dead or dying material.  

Why? Removing dead plants and creating space between trees and shrubs creates a buffer for your property and reduces potential fuel for fire.  

What to do:

1. Remove all dead plants, grass, and weeds.
2. Remove dead or dry leaves and pine needles.
3. Trim trees regularly keep branches a minimum of 10 feet from other trees.

Create a separation between trees, shrubs, and items that could catch fire, such as patio furniture, wood piles, swing sets, etc.

Zone 2 – Reduce Potential Fuel Zone

Continue reducing potential fuel within 100 feet of the property line.

Why? 100 feet of defensible space is required by law. Public Resources Code (PRC) 4291

What to do:

1. Cut or mow annual grass down to a maximum height of four inches.
2. Create horizontal space between shrubs and trees. (See diagram)
3. Create vertical space between grass, shrubs and trees. (See diagram)
4. Remove fallen leaves, needles, twigs, bark, cones, and small branches. However, they may be permitted to a depth of three inches.
5. Keep 10 feet of clearance around exposed wood piles, down to bare mineral soil, in all directions.
6. Clear areas around outbuildings and propane tanks. Keep 10 feet of clearance to bare mineral soil and no flammable vegetation for an additional 10 feet around their exterior.

General Requirements for the entire Parcel:

·         Provide a minimum 15-foot vertical clearance above all roads, driveways, turnouts, and turnarounds providing fire department access to buildings.

·         Provide a minimum 3-foot clearance around all fire hydrants and fire water supply outlets.

·         “Outbuildings” and Liquid Propane Gas (LPG) storage tanks shall have a minimum 10-feet of clearance to bare mineral soil and no flammable vegetation for an additional 10-feet around their exterior. (Reference: CCR Title 14)

Local Ordinance:

San Luis Obispo County Ordinance is more restrictive than State laws. Where property is located in the Local Responsibility Area (LRA) serviced by San Luis Obispo County Fire, owners are required to provide a 100-foot defensible space on their property around any buildings, including buildings on neighboring properties. You are only responsible for the portion of the 100-foot zone that is on your property. (see attachment 1)

When a structure is less than one hundred feet from a property line and prohibited materials on an adjacent parcel present a fire hazard for the structure, the owner of the adjacent parcel where the fire hazard exists shall be responsible for clearing the area on that owner’s parcel that is within one hundred feet of the structure, to provide the necessary fire protection.

Property without buildings are also subject to the 100-foot defensible space requirements if the property is less than 100-feet from any building on neighboring properties.

Lots one acre or more require mowing or disking of a thirty foot (30’) wide break around the property perimeter cut down to 4” in height

The following shall be exempt from the requirements of this Chapter:

(1)    Fenced pastures where existing livestock will significantly reduce weeds and grasses.

(2)     Growing hay and grains that will be cut at harvest time; any hay or grain uncut will be subject to abatement.

(3)    Vineyards when vineyard rows are maintained down to dirt or have minimal vegetation not exceeding 4” mowed height.

(4)    Single specimens of trees, ornamental shrubbery, or cumulative groundcover such as irrigated green grass, ivy, succulents or similar plants used as groundcover, provided they do not form a means of readily transmitting fire.

How to Space Trees and Shrubs

Vertical Clearance

Maintain space between the lowest tree branches and the ground or shrubs.

• Remove all tree branches at least six 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 treetops like a ladder. This leads to more intense fire closer to your home.
• Keep at least three times the height of any shrubs between the shrubs and the lowest branches of trees.

• Example: A 5-foot shrub is growing near a tree. 15 feet of clearance is needed between the top of the shrub and the lowest tree branch.

Horizontal Clearance

Horizontal space depends on the slope of the land and the height of the shrubs or trees. Leave more space between vegetation on steeper slopes. Refer to the chart below to determine spacing distance.

Space between shrubs:

• Flat or mild slope (less than 20%): Two times the height of the shrub.
• Mild to moderate slope (20-40%): Four times the height of the shrub
• Moderate to steep slope (greater than 40%): Six times the height of the shrub

Space between trees:

• Flat or mild slope (less than 20%): 10 feet.
• Mild to moderate slope (20-40%): 20 feet.
• Moderate to steep slope (greater than 40%): 30 feet.

Fire Smart Landscaping

Help prevent the spread of wildfires with fire-smart landscaping practices. Developing a fire-smart landscape goes beyond just maintaining a neat yard. It involves choosing and placing fire-resistant plants that thrive in California’s dry climate. Fire-smart landscaping is cost-effective too, as it conserves water and can increase your property value.

For tailored advice on fire-resistant plants perfect for your area, check with local nurseries, landscape contractors, or your county’s UC Cooperative Extension service. They can guide you in creating an effective, affordable fire-smart landscape. CAL FIRE also provides helpful information in on our Fire Smart Landscaping Website.

Home Hardening:

An important part of defensible space is to limit the intrusion of embers and flame into the home and buildings. Property owners can take further advantage of proper defensible space by hardening their home and buildings. Areas to review and upgrade include roofs, gutters, eves, vents, walls, siding, trim boards, windows, door openings, decks, and patio covers.