Zone 1 is your home and attached structures. It includes the house, attached decks, fences, and other combustible structures.
• Maintain a non-combustible area within 3 feet of a house. This can include pavement, rocks, gravel, and irrigated non-woody plants like lawn, small flowers, and low ground covers. Do not use flammable mulches or allow dead plant material to accumulate.
Zone 2 is your landscape extending 100 feet from the home. It is kept clean and green, with groups of well-maintained and irrigated turf, ground covers, and other perennial plants separated by rock or other non-combustible surfaces or walls. Scattered trees and shrubs are pruned and kept well away from the home. Zones 1 and 2 together make up the home ignition zone or defensible space.
• Trees can be left in Zone 2 for shade and esthetics, but should be widely spaced. Leave at least 10 feet between mature tree crowns or small groups of trees or shrubs to keep fire from easily moving across the landscape. Favor broadleaved trees and small trees, and avoid resinous conifers. Remove all dead trees and shrubs
• Keep tree crowns at least 10 to 15 feet horizontally from structures, chimney outlets, and powerlines. Pruning near powerlines should be done by the power company. Prune without leaving stubs that cause sprouting and decay
• Brush and low limbs provide a “fire ladder” for low fires to move into taller trees. Break up this ladder by removing shrubs and small trees near larger trees. Prune lower tree branches to keep a 6 to 15 foot clearance from the ground to the bottom of the crown. However, at least half of the tree’s crown should be left with live branches to ensure its health
• Keep this zone clean and green. Remove accumulated woody debris, dry herbaceous material, and dead needles. Mow lawns, prune shrubs and trees to remove dead wood, and thin and prune ground covers and other vegetation.
• Keep Zone 2 well watered according to plant needs. Plants with sufficient moisture will be less flammable. Avoid over-watering, which can cause excess growth.
• Store firewood 30 to 100 feet from structures. Locate propane tanks well away from your home according to code (contact your fire department). Keep flammable materials, including tree crowns, other vegetation, and wooden fences, at least 15 feet from firewood and propane tanks
Zone 3 is the surrounding native or wildland area. Its vegetation should be thinned if feasible, with a focus on removing highly flammable vegetation and debris. Note that these distances are for level properties with moderate vegetation densities. They need to be increased up to 200 feet on steeper slopes with dense vegetation.
• This zone can be left fairly natural, but pruning and thinning trees and brush is beneficial.
• Thin dense tree groups to slow fire spread. Also remove brush that provides a “fire ladder” into tree crowns.
• Prevent buildup of dead plant material and litter. Do not pile brush removed from elsewhere in this zone; get rid of it. Neighbors may want to get together to sponsor cleanup days, with a chipper and truck available for debris removal.
For more information: https://extension.usu.edu/ueden/ou-files/Firewise-Landscaping-for-Utah.pdf