Colorado's rules changed on 1 July 2026 — and they work differently in every county. Some are based on square footage, some off mapped zones, and in parts of the state, your fire district decides rather than your county.
Colorado's Wildfire Resiliency Code Board adopted the statewide code on 1 July 2025. Every jurisdiction with land in the wildland-urban interface had to adopt it — or something meeting or exceeding it — by 1 April 2026, and enforce it from 1 July 2026.
Most Colorado counties now have defensible space and structure hardening requirements attached to the building permit process. What differs enormously is what triggers them, who administers them, and what a passing inspection looks like.
It is not retroactive. This is the single most common misunderstanding, and it is worth being plain about: living in your existing home and not building anything does not require you to retrofit. The requirements attach when you apply for a permit.
It's non-refundable, but it carries forward. If the credit exceeds what you owe, you can carry the balance forward for up to five years.
The Board of County Commissioners approved the Jefferson County Wildfire Resiliency Code on 10 March 2026, together with an updated Wildland-Urban Interface Overlay District and a new WUI Overlay Map. All three took effect on 1 July 2026 for permits applied for on or after that date.
It applies to unincorporated Jefferson County only. Lakewood, Golden, Arvada, Morrison and the other municipalities set their own requirements — some stricter than the county's, some looser. Same storm, same shingles, different jurisdiction.
The boundary moved. The updated WUI Overlay Map classifies properties into Class 1 and Class 2 areas, and the boundary expanded. Properties that were previously outside it may not be now, so check your parcel on the county's interactive map rather than assuming.
Verification is done by a certified specialist. Someone building a structure must hire a certified wildfire mitigation specialist from the county's approved list to verify the defensible space — and to confirm that roads and driveways meet access standards so emergency vehicles can reach the property. That access piece catches more people out than the vegetation does.
The permits expire. Defensible space permits carry a three-year term, and property owners are legally required to maintain their clearings against vegetation regrowth. Mitigation in Jefferson County is not a one-time project.
Reroofing is treated differently. A complete reroof inside the mapped WUI must comply with the roofing provisions of the code, but reroofing alone does not automatically trigger a full-property defensible space requirement. Certain re-siding projects also qualify for a homeowner self-certification of the 0–5 foot ignition zone instead of a specialist inspection.
Jefferson County maintains a list of Certified Wildfire Mitigation Specialists approved to perform defensible space inspections. When the county issues a defensible space permit, that list is what the homeowner receives. Colorado Wildfire Mitigation is on it.
We also do the mitigation work. That means one company handles the plan, the clearing, and the inspection that signs it off — rather than coordinating a contractor and a separate inspector around a Certificate of Occupancy deadline while a general contractor waits on you.
It also means we build to a standard we apply ourselves, rather than guessing at someone else's reading of it.
Boulder County has the lowest triggers of any county we work in. Defensible space is required in unincorporated county for new residences, additions over 200 square feet, accessory structures over 120 square feet or sited less than 50 feet from a building containing habitable space, agricultural buildings over 200 square feet, all new and rebuilt decks, and exterior wall work affecting more than 25 percent of the total surface area of all exterior walls.
A rebuilt deck is enough. That is the threshold most homeowners are surprised by — work that feels like routine maintenance brings you fully into scope.
Zone matters. In Wildfire Zone 3, East County, defensible space is required for all new buildings and additions regardless of size. In Wildfire Zone 1, West County, any new covered projection, porch, deck or deck work requiring a building permit triggers it.
Zone 1 gives you two routes. You can follow the building code path, or obtain a Wildfire Partners certificate. If more than five years have passed since your last Wildfire Partners assessment, a new one is required.
Timing is the trap here. A wildfire mitigation assessment must be completed before your permit is issued — but the county's Wildfire Mitigation Team generally cannot schedule assessments until after a building permit application has been submitted. Once the application is in, a specialist contacts you. Build that sequence into your schedule rather than discovering it.
Park County works differently from its neighbors. Here, the fire protection district administers the requirement, not the county building department — and a lot of property owners find that out mid-project.
Check your district first. Living in Park County does not automatically put you in Platte Canyon Fire Protection District. Parts of Woodside and the majority of Will-O-Wisp fall under Elk Creek instead, and applying to the wrong district wastes weeks.
In the Platte Canyon district, a Conditional Wildfire Hazard Permit is required for new construction or any addition of 200 square feet or greater. The fee is $150 and covers all inspections.
The process runs in two inspections. You apply, then an initial inspection produces a written list of mitigation requirements with trees flagged for removal. You do the work, then call for the final inspection. Pass, and Platte Canyon notifies the Park County Building Department that the Wildfire Hazard Standards were met. Fail, and there is a $50 re-inspection fee.
What the final inspection actually checks: every designated tree down, remaining trees and vegetation pruned to 8 to 10 feet, all created slash treated — chipped, burned or removed — firewood piled upslope of the structure, and every item on the inspection checklist complete. That slash requirement is where most self-done projects stall.
Every one of these counties had the same 1 July 2026 deadline, and most now have requirements attached to building permits. What varies is the trigger and the administrator.
Some key off square footage, some off elevation, some off mapped fire intensity zones. Some counties handle it themselves; in others the fire protection district does. A few municipalities within these counties run codes stricter than the county's.
We work across all of them, and the honest answer for any specific parcel is that it needs checking rather than assuming. Tell us the address and we will find out what applies before you commit to anything.
If you are early enough in planning, that phone call is worth making before you finalise a design — several of these requirements affect siting, access, and materials rather than just landscaping.
Defensible space gets the attention, but these codes cover the building itself. In Jefferson County the structure hardening requirements include Class A roofing assemblies, siding and deck framing materials that limit ignition, noncombustible deck surfaces, performance standards for ventilation openings to prevent ember intrusion, nonflammable fencing within eight feet of structures, and a prohibition on certain highly flammable plants — junipers among them — within thirty feet.
Two of those catch people. A wood fence running into your siding is a wick leading to the house, and ornamental junipers sit against foundations across the Colorado foothills.
Structure hardening is generally reviewed through the normal building permit process, separately from the defensible space verification. See our home hardening page for what this involves in practice.
In Jefferson County, defensible space permits carry a three-year term and owners are legally required to maintain their clearings against regrowth. This is not a suggestion attached to the permit — it is a condition of it.
Vegetation regrows, needles fall every year, and understory comes back faster than most people expect. Defensible space created in 2023 is not defensible space today.
If you permitted work around 2023 or 2024, you are at or near the point where it needs looking at again. We offer pre-season maintenance visits on properties we have treated, and we will tell you when yours is coming due.
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Do I have to retrofit my existing home?A: No. None of these codes are retroactive. They attach to permits for new construction and qualifying exterior work.
Does a reroof trigger a full defensible space requirement?A: 25% of up to $2,500 in qualifying costs, so $625 at most. Modest against a large project, but it's money back on work you were doing anyway.In unincorporated Jefferson County, no. A reroof inside the mapped WUI must meet the roofing provisions of the code, but it does not by itself require a full-property overhaul. Other jurisdictions may differ.
Who can perform the inspection?A: In Jefferson County, a certified wildfire mitigation specialist from the county's approved list. We are on that list, and we can also do the mitigation work.
How long does the permit last?A: In Jefferson County, three years — with an ongoing legal obligation to maintain the cleared area. Other counties vary.
I'm inside a city. Do county rules apply?A: Generally not. Municipalities set their own requirements, and several Colorado cities have codes stricter than their surrounding county. Start with your city building department.
Last verified: August 2026
Sources: Jefferson County Planning & Zoning; Boulder County Community Planning & Permitting; Platte Canyon Fire Protection District; Colorado Wildfire Resiliency Code Board.
This page is a guide, not a determination. Only your county, municipality or fire protection district can tell you what applies to your parcel, and these requirements changed across Colorado in 2026. Confirm before you budget, order materials or schedule work.
Free on-site assessment across the Colorado foothills. We'll tell you which requirements apply to your parcel, what the sequence looks like, and what the work would cost — before you commit to anything.
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