Boise, ID Environmental Rules: Defensible Space (2026)
Key Facts
- Minimum defensible space
- 30 feet from structure
- Fuel-free zone
- 5 feet, fire-resistant only
- Tree crown clearance
- 10 feet from structures
- Applies to
- WUI-designated areas only
- Pre-2011 buildings
- Exempt unless hazard found
Summary
Boise requires a 30-foot defensible space around homes in designated Wildland-Urban Interface areas, with a 5-foot fuel-free zone right against structures.
4115.3 Fuel Modification. Buildings or structures in designated wildland-urban interface (WUI) areas, shall comply with defensible space fuel modification distances as required by the code official. Fuel modification distance shall be at least 30 feet... 4115.3.4 Fuel-Free Area. A fuel-free area of 5 feet is required around all structures. This area shall utilize and maintain only approved fire-resistant vegetation and noncombustible mulches (e.g. rock mulch).
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-31: Code current through: Ord. 20-26, passed 6-9-2026).
Full Breakdown
Under Boise City Code § 5-12-53, which adopts International Fire Code Chapter 41 for the city's Wildland-Urban Interface (WUI) areas, buildings must maintain a fuel modification zone of at least 30 feet measured horizontally from the structure, extendable by the fire code official based on a required Wildfire Safety Plan. A 5-foot fuel-free area right around the structure must use only fire-resistant vegetation or noncombustible mulch like rock. Property owners, lessees, and operators are personally responsible for clearing non-fire-resistive vegetation and keeping the space maintained year-round, including removing dead leaves and needles from roofs.
Violations & Fines
Fire code official can order defensible space work and cite property owners/lessees who fail to modify or maintain the zone; existing pre-2011 structures are exempt unless the fire official finds a distinct hazard to life or property.
Frequently Asked Questions
Does defensible space apply to every Boise property?
Can I keep trees inside the defensible space?
Sources & Official References
Other rules in Boise
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