Arapahoe County, CO Environmental Rules: Defensible Space (2026)
Key Facts
- Governing section
- LDC § 4-1.4.E.10, Wildfire Defensible Space
- Noncombustible clearance
- 3 ft beyond walls, 5 ft beyond eaves/driplines
- Gravel/rock spec
- 3/4-inch minimum, 2 inches thick
- Fence/wall material rule
- Noncombustible within 5 ft of building
- Grass height limit
- Mown to 4 inches maximum near structures
Summary
Every structure in unincorporated Arapahoe County must keep a noncombustible buffer: gravel or crushed rock at least two inches thick beneath decks and around the foundation, extending three feet past exterior walls and five feet past eave and deck driplines. Walls, fences and retaining walls within five feet of a building must be noncombustible, and grass near structures must stay mowed to four inches or less.
j. Wildfire Defensible Space Colorado's population is growing, its urban and rural areas are rapidly expanding, and landowners need to know how to correctly landscape their property to reduce wildfire hazards. The following standards apply to all structures. i. Gravel or crushed rock not less than ¾-inch in diameter or other non-combustible material applied at least two inches thick must be installed beneath decks, unenclosed floors, and around the perimeter of the building to extend at least three feet beyond the exterior walls and at least five feet beyond the driplines of decks, bay windows, and other eaves and overhangs. ii. All building exterior walls, fences, and retaining walls within five feet of a building or other appurtenances that connect to buildings must be constructed of noncombustible materials or ignition-resistant materials. iii. Plant low-growing, non-resinous shrubs near structures. iv. Keep grass mown around structures to a maximum height of four inches.
Full Breakdown
10) opens by tying the rule directly to growth pressure in Colorado's wildland-urban interface and states plainly that the following standards apply to all structures, not just those in a mapped hazard overlay. The noncombustible clearance requirement is specific: gravel or crushed rock no smaller than three-quarter-inch diameter, or another non-combustible material, applied at least two inches thick, installed beneath decks and unenclosed floors and around the building perimeter, extending at least three feet beyond the exterior walls and at least five feet beyond the driplines of decks, bay windows, eaves and overhangs; poured concrete, asphalt, brick or stone pavers can substitute for gravel.
Within five feet of the building, or of any appurtenance connected to the building, every exterior wall, fence and retaining wall must be built of noncombustible or ignition-resistant material -- a rule that reaches ordinary residential fencing wherever it sits close to a house, not just the building's own walls. The section adds three maintenance-style standards: low-growing, non-resinous shrubs should be planted near structures; grass around structures must be kept mown to a maximum height of four inches; and a well-irrigated, hardscaped area should encircle the structure on all sides, including around decks and fences, to leave room for fire-suppression equipment during an emergency.
4, this defensible-space standard is a Landscaping and Screening chapter requirement applied during development review in unincorporated Arapahoe County; it does not reach structures inside Aurora, Centennial, Littleton or the county's other incorporated cities.
Violations & Fines
This subsection does not itself set out a dollar penalty; noncompliant plans are addressed through the LDC's general Chapter 6 enforcement and violations framework and through the same landscape-plan review, inspection and certificate-of-occupancy process used for the rest of Section 4-1.4's landscaping standards, rather than through a stand-alone fine schedule printed in the defensible-space text itself.
Frequently Asked Questions
Does the defensible-space rule apply only in designated wildfire-hazard areas?
Can my wood fence sit right against my house in unincorporated Arapahoe County?
How thick does the gravel buffer need to be?
Does this LDC rule apply to a house inside Aurora or Centennial?
Sources & Official References
Other rules in Arapahoe County
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