Colorado Wildfire & Defensible Space Rules by County in 2026: Post-Marshall Fire

The Marshall Fire changed Colorado wildfire policy more than any single event in the state's history. On December 30, 2021, a grass fire driven by 100-mph winds tore through Louisville and Superior, two suburban Boulder County towns that almost no one had categorized as wildland-urban interface. By the next morning, 1,084 homes were destroyed, two people were dead, and a billion-dollar question was on every county commissioner's desk: if a suburban tract development on flat grassland could burn that completely, what does "WUI" even mean in Colorado anymore? Four years later, the answer is showing up in county land use codes, municipal rebuild ordinances, and a brand-new state Wildland Urban Interface Code Board. Colorado homeowners in 2026 are operating under the strictest wildfire framework the state has ever had, and the rules are still being written. This guide walks through the state statutory framework, the post-Marshall response, the eight Colorado counties with the most active WUI regulation, and the specific defensible space, Class A roof, and construction requirements that determine whether your home meets code.

The state statutory framework

Colorado fire policy lives in two main places in state statute. CRS Title 25, Article 7 covers air quality and burning regulations, and CRS Title 24, Article 33.5 establishes the Department of Public Safety and the Division of Fire Prevention and Control (DFPC) — the state agency that maintains the Colorado Wildfire Information Resource Center, certifies wildland firefighters, and now houses the new state WUI Code Board. CRS 24-33.5-1201 et seq. is the operative section for DFPC's authority, and CRS 24-33.5-1226 specifically authorizes the division to assist local governments with wildfire mitigation planning.

The most consequential recent piece of legislation is HB 24-1007, signed by Governor Polis in May 2024 and codified at CRS 24-33.5-1234. It created the Wildland Urban Interface Code Board, a 17-member body housed under the DFPC and charged with developing a model wildland-urban interface code that local jurisdictions can adopt. The board includes county commissioners, fire chiefs, builders, insurers, and a tribal representative, and it has authority to recommend amendments to the International Wildland-Urban Interface Code (IWUIC) for Colorado-specific adoption. The board's first model code is expected for adoption in 2026, with a recommendation that jurisdictions in identified WUI areas adopt it by 2027. HB 24-1007 does not mandate adoption — Colorado is a home-rule state and the legislature stopped short of preempting local building codes — but it creates strong political pressure for adoption, especially as insurance markets harden.

The 2024 session also produced HB 24-1006, which expanded the Wildfire Mitigation Grant Program administered by DFPC, offering up to $2 million per county for fuels reduction, defensible space outreach, and home hardening assistance with matching requirements of 25% to 50% depending on community wildfire risk classification.

Underneath those statutes is the model code framework. Colorado does not have a mandatory statewide building code; cities and counties adopt their own. But the standards everyone gravitates toward are the International Building Code (IBC) Chapter 7A (Materials and Construction Methods for Exterior Wildfire Exposure), the International Wildland-Urban Interface Code (IWUIC) — most jurisdictions are working from the 2021 IWUIC, with 2024 IWUIC adoption coming in 2026 — and NFPA 1144 (reducing structure ignition hazards). The new state model code under HB 24-1007 will pull elements from all of them.

The Marshall Fire and what came after

The Marshall Fire matters not just because of the loss of life and property, but because it broke the assumption that WUI risk in Colorado is a mountain-and-forest problem. The fire started in grassland south of Boulder, jumped Highway 36, and entered Louisville and Superior — two of the most suburban, master-planned communities in the Denver metro. Most of the destroyed homes were not in any pre-existing WUI overlay zone. They were on cul-de-sacs with manicured lawns. The fire spread by ember showers landing on wood-shake roofs, accumulating in gutter debris, and igniting wood fence sections that ran continuously from neighbor to neighbor.

The local response was immediate. Louisville passed its rebuild ordinance in March 2022 (Louisville Municipal Code Title 15), waiving certain permit fees but layering new fire-resistance requirements on every rebuild. Rebuilds in the burn area must use Class A roofing assemblies, ignition-resistant exterior siding (cement fiber, stucco, or equivalent meeting ASTM E84 Class A flame spread), tempered or dual-pane windows on elevations facing vegetation, ember-resistant attic and crawl space vents (meeting ASTM E2886 or California State Fire Marshal listing), and a five-foot non-combustible zone (Zone 0) around the home. Wood-shake roofs, formerly allowed, are now prohibited on any new construction or substantial reroof. Superior adopted parallel requirements in Town Code Title 18, with additional restrictions on wood fence sections attached to the home (the first six feet of any fence attached to a structure must be non-combustible to prevent fence-to-house ember pathways).

Boulder County adopted Land Use Code amendments in late 2022 and 2023, codifying defensible space requirements in unincorporated Boulder County and updating the Wildfire Zones map. Boulder County Land Use Code Article 4-1100 (Wildfire Mitigation) now requires a defensible space plan for any new residential construction or substantial improvement in a designated Wildfire Zone, and Class A roof assemblies for any reroof in Wildfire Zones 1 and 2. The county also established Wildfire Partners — a free home assessment service that certifies completed mitigation work, a designation increasingly recognized by insurers.

Defensible space: the three-zone framework

Defensible space is the single most consistent requirement across Colorado WUI jurisdictions, and the framework is borrowed from the Colorado State Forest Service and NFPA 1144. It divides the area around a home into three zones, each with different vegetation rules:

Zone 1, the immediate or noncombustible zone, runs from 0 to 5 feet from the structure. This zone — added to the NFPA framework in 2022 in response to Marshall and other ember-driven fires — requires no combustible materials: no wood mulch, no plastic edging, no wood fencing attached to the home, no stored firewood, no juniper or other resinous shrubs. Recommended ground covers are gravel, river rock, decorative stone, or bare mineral soil. Boulder County, Louisville, and Superior all require Zone 0 (the 0-5 foot zone) compliance for any new construction or substantial improvement. El Paso County's defensible space guidance recommends but does not yet mandate Zone 0.

Zone 2, the lean-clean-and-green zone, extends from 5 to 30 feet. Vegetation is allowed but must be widely spaced (a recommended minimum of 10 feet between tree crowns), well-irrigated, and free of dead material. Wood mulch is permitted but should be thin (under 2 inches) and broken up by stone pathways. Wood piles, propane tanks, and other combustibles must be moved out of this zone or screened by non-combustible barriers.

Zone 3, the reduced fuel zone, runs from 30 to 100 feet (extended to 200 feet on slopes greater than 10%). Native vegetation can remain, but ladder fuels — brush and small trees under tall trees that can carry fire vertically — must be removed, and tree canopy spacing should allow at least 10 feet between crowns. Dead and dying trees must be removed, and grasses kept under 6 inches in summer.

Colorado does not have a state statute that mandates these zones for all homeowners — that would require legislation the home-rule counties have resisted. But several counties impose them through local ordinance, and HOAs are increasingly preempted from prohibiting defensible space work. SB 22-006, codified at CRS 38-33.3-106.5, prohibits HOAs from banning fire mitigation activities including the removal of trees and the use of non-combustible materials in defensible space zones, overriding any CC&R that requires wood shingles, prohibits gravel landscaping near the foundation, or otherwise blocks reasonable fire mitigation.

Boulder County

Boulder County is the most aggressive WUI regulator in Colorado and the case study every other county is watching. The Boulder County Land Use Code Article 4-1100 (Wildfire Mitigation) divides the county into Wildfire Zones 1, 2, and 3 based on fuel load, slope, and access. Zone 1 (high hazard) requires a Boulder County Wildfire Mitigation Plan approved before any building permit, professional defensible space implementation, Class A roof assemblies on all new construction and reroofs, ignition-resistant exterior cladding (IBC Chapter 7A materials), and ember-resistant venting throughout. Zone 2 (moderate) requires the same Class A roof and ignition-resistant cladding but allows homeowner-implemented defensible space. Zone 3 (lower hazard) requires Class A roofs on new construction but more flexibility on other elements.

The county also operates Wildfire Partners (BoCo.org/wildfirepartners), a free on-site home assessment program. A trained assessor walks the property, documents 30+ specific risks, and produces a written report. Homeowners who complete the recommended mitigation work receive Wildfire Partners certification, which several insurance carriers — including USAA, State Farm, and Allstate's Colorado affiliates — now accept as evidence of reduced risk eligible for premium credits or, more importantly, eligibility for renewal in markets where insurers are non-renewing en masse.

The cities of Boulder, Louisville, Superior, and Lafayette have their own building codes that exceed the county standard, and the unincorporated areas (Eldorado Springs, Gold Hill, Jamestown, Nederland surrounds) are governed by the Land Use Code. Boulder city itself adopted IBC Chapter 7A by reference in 2023 for all new construction in identified hazard areas.

Louisville and Superior (rebuild zones)

The Louisville and Superior rebuild codes are worth understanding even outside the burn area because they preview what other Front Range cities are likely to adopt. Both ordinances require: Class A roof coverings (asphalt shingle Class A, metal, tile, or equivalent listed assembly under UL 790); ignition-resistant siding meeting ASTM E2768 or installed per IBC Chapter 7A Section 705A; tempered glass on elevations facing vegetation; ember-resistant attic and foundation vents; Zone 0 (5-foot noncombustible zone) at the foundation perimeter; gutters with metal leaf guards or non-combustible filler; and a prohibition on wood-shake or wood-shingle roof coverings on any residential structure.

Louisville Municipal Code 15.04 incorporates the 2021 IBC with local amendments, and Section 15.04.140 codifies the post-Marshall wildfire amendments. Superior Town Code Chapter 18.30 (Wildfire-Resistant Construction) does the same for Superior. Both ordinances extended the rebuild standards to substantial improvements outside the burn footprint, meaning that any major remodel or addition now triggers compliance.

El Paso County and Colorado Springs

El Paso County's wildfire memory is the Waldo Canyon Fire (2012, 346 homes destroyed) and the Black Forest Fire (2013, 489 homes destroyed and two deaths). The county's response is the El Paso County Land Development Code (LDC) Chapter 8.4, Wildfire Hazard Mitigation. The LDC designates Wildfire Hazard Areas based on a county hazard map and requires a Wildfire Mitigation Plan for any new residential subdivision in those areas. Individual lot owners building a single-family home in a designated hazard area must demonstrate compliance with defensible space standards before final inspection.

Colorado Springs Municipal Code (CSMC) Article 7, Chapter 7.7, adopts the 2018 IWUIC with local amendments for areas identified on the city's Wildland-Urban Interface map. New construction in those areas must comply with IWUIC ignition-resistant construction requirements (Class 1, 2, or 3 depending on hazard severity), and the fire department conducts pre-occupancy inspections for defensible space compliance.

El Paso County's Wildfire Hazard Mitigation grant program reimburses homeowners up to $1,500 for defensible space work and up to $5,000 for fire-resistant home hardening (Class A roof replacement, ember-resistant venting, ignition-resistant cladding).

Larimer County and Fort Collins

The Cameron Peak Fire of 2020 burned 208,913 acres, making it the largest wildfire in Colorado state history at the time. It destroyed 469 structures in Larimer County, including homes in Glen Haven, Crystal Lakes, and Red Feather Lakes. The East Troublesome Fire that same year burned another 193,000 acres in Grand and Larimer counties. The combination forced an update to the Larimer County Land Use Code (LCLUC) Section 4.2.2 (Wildfire Hazard Area Standards), which now applies to all unincorporated parts of the county west of I-25.

LCLUC 4.2.2 requires every new residential structure in a Wildfire Hazard Area to use Class A roof coverings, ignition-resistant exterior wall coverings, ember-resistant attic and foundation vents, and defensible space per Colorado State Forest Service guidance. The county Wildfire Mitigation Office reviews defensible space plans before issuing a building permit and conducts a final inspection before certificate of occupancy. The county also operates a free slash chipping program.

Fort Collins city code (Land Use Code Article 5, and Municipal Code Chapter 5, Article III) adopts the 2021 IBC and IWUIC by reference and identifies WUI areas primarily on the foothills west of the city. The Poudre Fire Authority runs a Ready, Set, Go! program and offers home assessments.

Jefferson County

Jefferson County contains the densest WUI in the Denver metro: Conifer, Evergreen, Genesee, Pine, and the foothill subdivisions from Golden south to Sedalia. Jefferson County Zoning Resolution Section 33 (Wildfire) requires a Wildfire Hazard Evaluation for any new building permit in identified Wildfire Hazard Severity Zones, and compliance with Jefferson County Defensible Space Guidelines for any new home or major addition.

For new subdivisions, Jefferson County imposes a Wildfire Mitigation Plan requirement under subdivision regulations (Section 23.D), requiring developers to demonstrate two means of access for subdivisions over 30 lots, NFPA 1142 fire flow water supply, and a 30-year vegetation management plan for common areas. The Jeffco Wildfire Resilience program partners with local fire protection districts to provide free home assessments and grants.

Douglas County

Douglas County south of Denver is one of the fastest-growing counties in Colorado, with much of the new development in the foothills west of I-25 — Castle Pines, Sedalia, Roxborough Park, Perry Park. The Douglas County Zoning Resolution Section 17 (Wildfire Hazard Mitigation Areas) designates WHM Areas based on a hazard map and imposes Class A roof requirements, ignition-resistant cladding, ember-resistant venting, and defensible space on all new residential construction.

Douglas County is unusual in that it has fully adopted the 2018 IWUIC by reference for its WHM Areas, automatically incorporating IWUIC construction class assignments (Class 1, 2, or 3 ignition-resistant construction depending on hazard rating and fire flow). The county's Wildfire Mitigation Program, run jointly with West Metro Fire Rescue and South Metro Fire Rescue, offers matching grants up to $1,000 per property. Roxborough Park HOA covenants now affirmatively require Class A roofs and ignition-resistant siding for all new construction.

Summit County (Breckenridge, Frisco, Dillon)

Summit County is mountain WUI in its purest form: dense lodgepole pine, beetle-killed standing dead trees, narrow canyon access, and a population that triples on ski weekends. The Summit County Land Use Code Section 3505 (Wildfire Regulations) divides the county into Wildfire Hazard Areas based on the Community Wildfire Protection Plan and imposes Class A roof, ignition-resistant siding, and defensible space requirements on all new construction.

Breckenridge Municipal Code Chapter 9, Article 8 (Wildfire Mitigation) extends the requirements within town limits, and the town runs a Wildfire Council that funds slash chipping and ember-resistant vent replacement grants. Frisco and Dillon have adopted similar local codes. Summit County is one of the few in Colorado that requires registration and inspection of outdoor wood-burning fire pits in WUI areas, and imposes restrictions on stored firewood within 30 feet of structures.

Eagle County (Vail, Beaver Creek, Avon)

Eagle County Land Use Regulations Article 5 (Wildfire Mitigation) operates similarly to Summit's, with mapped Wildfire Hazard Zones and Class A roof, ignition-resistant cladding, and defensible space requirements. Eagle County added a specific requirement after the 2018 Lake Christine Fire (which destroyed three homes in El Jebel): all new residential construction in mapped WHZs must provide a five-foot noncombustible Zone 0 at the foundation perimeter, prohibiting wood mulch, attached wood fencing, and combustible plantings within that distance.

Town of Vail Municipal Code Chapter 14 (Development Standards) requires Class A roofing and ignition-resistant siding for all new construction, and Vail's architectural review process now formally incorporates fire-resistance criteria. Avon and Eagle have parallel requirements. Eagle County runs the Wildfire Adapted Partner program, modeled on Wildfire Partners in Boulder.

Denver and Aurora

Denver and Aurora are not traditional WUI jurisdictions — they are largely urban with limited wildland adjacency — but both cities adopted updated codes after Marshall that bear mentioning. Denver Revised Municipal Code Building Code (DBC) updates effective 2023 require Class A or B roofing on all new residential construction citywide (not just in WUI areas), reflecting the lesson from Louisville and Superior that "wildland-urban interface" can include suburban grassland edges. Aurora made similar updates, and both cities now require ember-resistant venting on new construction in their respective foothill or grassland-adjacent neighborhoods.

For homeowners in Denver and Aurora, the bigger issue is insurance. Both cities have seen non-renewal rates spike as carriers re-evaluate Colorado risk, and homes with wood-shake roofs (still legal in most existing housing stock under grandfathering) are particularly vulnerable to non-renewal even within city limits.

The insurance crisis

Colorado has the second-highest homeowners insurance non-renewal rate in the country, behind only California. According to the Colorado Division of Insurance's 2024 Wildfire and Insurance Report, more than 7% of policies in identified high-risk wildfire zones were non-renewed in 2023, and the trend continued through 2025. Carriers including State Farm, Allstate, USAA, and Travelers have narrowed their Colorado underwriting criteria, with several declining to write new business in ZIP codes with a high USFS Wildfire Hazard Potential rating.

The state response combines consumer protection — HB 23-1174 requires insurers to give 60 days' notice before non-renewal for wildfire risk and disclose the specific risk factors — with direct intervention. The Colorado FAIR Plan, the state's insurer of last resort, expanded in 2024 to provide wildfire coverage where private insurance is unavailable. As of late 2025, more than 12,000 Colorado homes were covered by the FAIR Plan, up from fewer than 1,500 in 2022. Defensible space and home hardening are no longer just safety measures — they are increasingly insurance requirements. Wildfire Partners certification, IBHS Wildfire Prepared Home designation, and equivalent local programs are the only way many homeowners in high-hazard ZIP codes can secure or maintain a policy.

Grant programs and where to get help

The state Wildfire Mitigation Grant Program (administered by DFPC under CRS 24-33.5-1226 and expanded by HB 24-1006) is the largest source of funding. Counties apply for the funds and pass them through to homeowners via local matching grants. Boulder, Larimer, El Paso, Jefferson, Douglas, Summit, Eagle, and Garfield counties all operate active pass-through programs. Federal funding through the USDA Forest Service Community Wildfire Defense Grant program supplements the state funds, with a particular focus on under-resourced communities.

Tax credits also help. The Colorado Wildfire Mitigation Income Tax Credit (CRS 39-22-535) provides a state income tax credit equal to 25% of qualifying wildfire mitigation expenses up to $2,500 per year. Qualifying expenses include defensible space work, ignition-resistant retrofits, and professional assessments. The credit was renewed and expanded in 2024 and is currently scheduled to remain in effect through 2030.

For homeowners trying to navigate all of this, the practical starting point is your county's wildfire mitigation office or fire protection district. Every county we cover in this guide has a free home assessment program, and most have a defensible space resource website with maps, applicable code references, and grant applications. The Wildfire Partners model from Boulder County has been so successful that several other counties are replicating it under their own names — Wildfire Adapted Partners in Eagle, Jeffco Wildfire Resilience in Jefferson, and so on.

What to do as a Colorado homeowner

Six questions to answer before you assume your home meets code: Is your property in a designated Wildfire Hazard Area on your county's map? If yes, when was your roof last replaced and is it a Class A assembly? Is your exterior cladding ignition-resistant, or is it wood siding installed before 2015? Do your attic and foundation vents have ember-resistant screens (1/8" mesh minimum, with listed ember-resistant products preferred)? Do you have a 5-foot noncombustible Zone 0 at the foundation? Is your defensible space (Zones 1, 2, 3) implemented and maintained, and is the documentation current with your insurer?

If you answered "no" or "I don't know" to any of these, your county wildfire mitigation office can do a free assessment that produces a punch list. CityRuleLookup tracks fire code requirements for every Colorado county and many cities under the Fire Regulations category, including defensible space rules, open burning restrictions, and outdoor fire pit standards. Start there to confirm what specifically applies to your jurisdiction, then schedule the free assessment, then check with your insurer about which certifications they recognize for premium credits or renewal eligibility. In post-Marshall Colorado, the cost of not knowing has gotten very high.