The Colorado Wildfire Resiliency Code and Your Greenhouse
Colorado jurisdictions in mapped wildland-urban interface areas were required to adopt wildfire construction standards meeting or exceeding the state minimums, with local implementation required by July 1, 2026.
For most greenhouse projects, the key questions are:
- Is the property inside the locally mapped wildfire area?
- Will the greenhouse be classified as a Group U structure?
- Will it be located more than 50 feet from structures containing occupiable or habitable space?
- Has the local jurisdiction amended the state model code?
This guide summarizes the Colorado state model standards. The code, map, and amendments adopted by your city, county, fire district, or other local authority control your project. Your local code official makes the final occupancy, code, and permit determinations.
Last updated July 2026.
The Main Takeaway
Under the unamended state model code, a greenhouse classified as Group U may qualify for an exemption from wildfire structure-hardening requirements when it is sufficiently separated from occupiable or habitable structures.
IBC Section 312.1.1 classifies a greenhouse as Group U when it is not assigned another occupancy based on its use.
Two state model provisions address separation:
- CWRC Section 401.1, Exception 1, uses “at least 50 feet” for an exception from Chapter 4 structure-hardening requirements.
- CWRC Section 102.10(8) uses “more than 50 feet” for a broader exemption covering qualifying Group U accessory and agricultural structures.
Because the wording differs, avoid designing to exactly 50 feet where the site allows more separation. Confirm the required distance and measurement method with the local official.
Separation may resolve the CWRC structure-hardening question. It does not eliminate ordinary zoning, setbacks, structural design, snow and wind loading, foundation, electrical, fire-access, or permit requirements.
The law also includes an exclusion for a qualifying thirty-five-acre parcel with only one residential structure that does not abut a residential or commercial area. Confirm eligibility rather than assuming all parcels larger than 35 acres qualify.
How to proceed
Step 1: Determine whether the code applies
Identify the authority having jurisdiction. Depending on the property, that may be a city, county, fire protection district, or another local agency.
Then confirm:
- Whether the parcel is inside the locally designated wildfire area
- The applicable Fire Intensity Classification: Low, Moderate, or High
- Which wildfire code or ordinance the jurisdiction adopted
- Whether the state model provisions were locally amended
Use the currently effective ordinance and map. Older handouts and draft ordinances may no longer reflect the rules in force.
Step 2: Confirm the greenhouse classification
A greenhouse used primarily as an accessory structure for growing plants may qualify as Group U.
A different classification may apply when the greenhouse includes:
- Classroom instruction
- Retail activity
- Events or agritourism
- Food preparation or processing
- Offices or work areas
- Regular public occupancy
- Other uses beyond normal plant cultivation
Commercial, educational, nonprofit, institutional, and public-access projects should confirm occupancy classification early. A different classification may affect building, accessibility, egress, plumbing, mechanical, and fire-protection requirements as well as the CWRC analysis.
Step 3: Confirm the separation
Ask the local official:
- Does the jurisdiction apply the Group U exemption or exception to this greenhouse?
- Is the required separation at least 50 feet or more than 50 feet?
- From which points on the structures is the distance measured?
- Which occupiable or habitable structures must be included, including any on adjacent property?
- Will the department confirm its determination in writing?
A written determination reduces ambiguity for the owner, supplier, installer, designer, and reviewing department.
What if the greenhouse must be located within 50 feet
A greenhouse within the separation distance is not necessarily prohibited, but the review becomes more project-specific.
| Consideration | Details | Action |
|---|---|---|
Glazing classification | The wildfire code and underlying building code distinguish among: Roof coverings, Skylights and sloped glazing, Window walls, Exterior walls, Light-transmitting plastic assemblies | Request a written determination identifying how the roof panels, wall panels, doors, vents, and lower wall sections will be classified. |
Ground-truthing | CWRC Section 304 allows review of a mapped wildfire hazard or fire-intensity classification when the map does not reflect actual site conditions. | This is not a general waiver and does not solve a separation issue by itself. Supporting documentation from a qualified wildfire professional may be required. |
Alternative materials or modifications | CWRC Sections 104.2.2 and 104.2.3 allow the local official to consider alternative materials, methods, or case-specific modifications. Approval is discretionary and may require: Test reports, Engineering analysis, Product evaluation reports, Manufacturer documentation, Fire-performance evidence, Independent review | Ask what documentation the jurisdiction requires before investing in a formal submission. |
About polycarbonate and fire classifications
Growing Spaces uses multiwall polycarbonate classified as CC1 under the building code provisions for light-transmitting plastics.
CC1 is not equivalent to a Class A roof classification.
Class A ratings under ASTM E108 or UL 790 apply to a tested roof covering or roof assembly under exterior fire exposure. Growing Spaces’ current greenhouse glazing assembly is not listed as a Class A roof assembly under those standards.
We can provide available product specifications and testing documentation, but the local authority determines whether the materials satisfy the requirements for a particular project.
Existing greenhouses and later work
A lawful existing greenhouse may generally continue in use after adoption of a new code.
Additional requirements may apply to:
- Relocation
- Additions
- Changes of use or occupancy
- Substantial roof or wall replacement
- Repairs exceeding an applicable threshold
- Unsafe conditions
The model code contains different provisions for different types of exterior work. Confirm the proposed scope with the local building department before beginning work.
Growing Spaces is always available to troubleshoot or maintain your dome.
What Growing Spaces can do
For a proposed Colorado project, Growing Spaces can help:
- Review the publicly available wildfire map
- Identify the likely authority having jurisdiction
- Review the proposed greenhouse location
- Assemble available product documentation
- Prepare questions for the local official
Growing Spaces does not make the final occupancy, code, or permit determination.
We have also requested written guidance from the Colorado Wildfire Resiliency Code Board concerning glazed horticultural structures and are supporting clearer greenhouse language in future code editions.
Call 800-753-9333 or contact us to discuss a proposed project.
Sources and scope
- Colorado Wildfire Resiliency Code Board State program information, code resources, mapping, and board materials.
- Colorado Code of Regulations: 8 CCR 1507-39 Official state rule adopting the Colorado Wildfire Resiliency Code and statewide fire-intensity map.
- 2025 Colorado Wildfire Resiliency Code, Version 1.0 Complete code text, including the exemptions, separation provisions, ground-truthing process, and alternative-materials provisions. This copy is hosted by the City of Lone Tree.
- Colorado Wildfire Resiliency State Code Map State map showing the wildfire area and Fire Intensity Classifications used for the code.
- Colorado Senate Bill 23-166 Legislation establishing the Wildfire Resiliency Code Board and requiring affected governing bodies to adopt and enforce wildfire codes meeting or exceeding the state standards.
- Colorado Senate Bill 25-142 Subsequent legislation revising the local adoption and implementation requirements.
- 2021 International Building Code, Chapter 3 See Section 312.1.1 for the Group U classification of greenhouses not classified as another occupancy.
- 2021 International Building Code, Section 2606.4 Defines the CC1 and CC2 classifications for light-transmitting plastic materials.
- ASTM E108-25: Fire Tests of Roof Coverings ASTM’s current standard describing Class A, B, and C exterior fire testing of roof coverings.
- UL Solutions: Roofing Testing and Certification Overview of roof-covering and roof-system testing under UL 790 and ASTM E108.
- California Office of the State Fire Marshal: Building in the Wildland California-specific information about Chapter 7A, wildfire construction requirements, and listed building materials.
Local amendments and later code editions may supersede portions of this guide.
Revision history
July 2026: Initial publication. Added state-model exemption analysis, local-jurisdiction guidance, occupancy questions, material-classification information, and permitting checklist.
