Boulder County, CO Fire Regulations: Brush Clearance (2026)
Key Facts
- Zones requiring full space
- Zone 1 and Zone 2
- Zone 3
- Full defensible space not required
- Addition trigger
- Over 200 sq ft
- Accessory trigger
- Over 120 sq ft
- Assessment
- Required before permit
Summary
In Wildfire Zone 1 (West County) and Wildfire Zone 2 (East County), Boulder County requires full defensible space around structures whenever you build, add over 200 sq ft, or add a large accessory structure. Standards include ignition-resistant construction and clearing combustible vegetation near buildings.
Unincorporated Boulder County is divided into three Wildfire Zones. Full defensible space is required in Wildfire Zone 1 - West County and Wildfire Zone 2 - East County. Full defensible space is NOT required in Wildfire Zone 3 - East County.
Full Breakdown
Boulder County's wildfire mitigation code, drawn from the International Wildland-Urban Interface (IWUI) Code and wildfire science, requires "full defensible space" in Wildfire Zones 1 and 2 (not Zone 3). Defensible space is triggered by new residences or commercial buildings, additions over 200 square feet, and accessory structures exceeding 120 square feet or located within 50 feet of habitable buildings. Requirements include a noncombustible band next to exterior walls, noncombustible fencing and retaining walls within 5-8 feet, and tree/brush thinning. A wildfire mitigation assessment must be completed before a building permit is issued; homeowners in Zone 1 may instead obtain a Wildfire Partners certificate.
Violations & Fines
Defensible space is enforced through the building-permit process. A permit will not be issued until the wildfire mitigation assessment and required clearing are completed.
Frequently Asked Questions
When do I have to create defensible space in Boulder County?
Is there an alternative to the building-code defensible space path?
Sources & Official References
Other rules in Boulder County
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