Jefferson & Clear Creek County’s New Wildfire Codes: What It Takes to Get Real Wood Siding to a Class A Rating

Class A Fire-Rated Wood Siding Colorado Wildfire Code – Looking for the full requirements checklist, including compliance triggers, exemptions, defensible space zones, permitting, and cost assistance? See HRTI’s complete guide to the Jefferson & Clear Creek County Wildfire Resiliency Code. This article focuses on one specific question that code raises: how real wood siding can still qualify.

What Changed: Colorado’s Wildfire Resiliency Code, Explained

Colorado’s statewide Wildfire Resiliency Code (CWRC) took effect July 1, 2025. The state required local jurisdictions to adopt the code, or a locally approved equivalent, by April 1, 2026, with enforcement that began July 1, 2026, and individual counties and municipalities are allowed to adopt stricter requirements based on local conditions. The code sorts properties into Wildland-Urban Interface (WUI) risk zones, generally described as Class 1 (lower to moderate fire intensity) and Class 2 (moderate to high fire intensity), with different required building-hardening measures for each.

Class 1 Zones Generally Require:

• Class A roof coverings
• Noncombustible gutters
• Ember- and flame-resistant attic and foundation vents
• Roof valley flashing installed over wide underlayment (roughly 36 inches)

Class 2 Zones Generally Require All of the Above, Plus:

• Exterior walls built from noncombustible materials, fire-retardant-treated wood, heavy timber, or another ignition-resistant material
• Multi-pane or tempered-glass windows
• Fire-rated exterior doors
• Noncombustible deck walking surfaces

Exact zone boundaries and documentation requirements vary by jurisdiction and can change as counties finalize their WUI overlay maps, so confirm your property’s specific classification with your local building department before finalizing material choices.

Jefferson County’s Updated Wildfire Resiliency Code (In Effect Since July 1, 2026)

Jefferson County’s Board of County Commissioners approved updates to the county’s own Wildfire Resiliency Code (WRC), along with updates to its Wildland-Urban Interface Overlay District map and zoning regulations, on March 10, 2026. The updated code took effect July 1, 2026. County officials have cited Jefferson County’s wildfire risk as higher than roughly 98% of U.S. counties as part of the rationale for the update.

• Who it applies to: unincorporated Jefferson County properties within the WUI overlay district only. Incorporated cities such as Golden, Lakewood, Arvada, Wheat Ridge, and Morrison have their own jurisdictions and codes.
• What triggers compliance: new buildings, additions, re-roofing, deck replacement, and re-siding or other exterior wall work that affects 25 percent or more of the home’s exterior wall area. Exempt: painting, staining, and similar maintenance, wall work affecting less than 25 percent of exterior wall area, historic structures where required to keep that designation, small detached accessory structures under 120 square feet, and fences more than 8 feet from a structure. The code is not retroactive, so it doesn’t require existing, unaltered exteriors to be brought up to the new standard on its own.
• What it requires: ignition-resistant materials for roofing (Class A assemblies), gutters, siding, windows, doors, decking, fascia, soffits, and ventilation openings. Fencing and retaining walls within 8 feet of a structure must also be noncombustible or ignition-resistant.
• Defensible space: defensible space is verified by a county-approved Wildfire Mitigation Specialist (for a re-siding permit, a homeowner may self-inspect), and is divided into Zone 1 (0 to 5 feet, essentially no combustible plants, mulch, or firewood storage), Zone 2 (5 to 30 feet, tree spacing and restrictions on certain species like junipers, arborvitae, and Gambel oak), and Zone 3 (30 to 100 feet, which applies only in higher-risk Class 2 areas).

Clear Creek County’s Wildfire Resiliency Code Requirements

Clear Creek County’s building department lists the 2025 Colorado Wildfire Resiliency Code among its currently adopted building codes, effective immediately per the county’s own building-codes page. Clear Creek County hasn’t published the same level of public detail on its specific WUI overlay zones and local amendments that Jefferson County has, so homeowners and builders there should confirm their property’s zone classification and any county-specific requirements directly with Clear Creek County’s Building Department (reachable through the Community Development division) before finalizing a siding, roofing, or deck project. See Clear Creek County’s Permits page to get started.

Other Foothills and Mountain Communities Affected

Jurisdiction matters here. Jefferson County’s code applies only to unincorporated Jefferson County, so incorporated cities like Golden, Lakewood, Arvada, Wheat Ridge, and Morrison follow their own codes. Mountain communities like Conifer are different: Conifer is an unincorporated Jefferson County community, so the county’s Wildfire Resiliency Code and WUI overlay district apply there for qualifying projects. Evergreen straddles the Jefferson and Clear Creek county line, so which rules apply there depends on your specific address. HRTI serves Evergreen, Golden, Morrison, and Conifer, along with the surrounding foothills, and Clear Creek County communities including Idaho Springs, Georgetown, and Empire are in some of the most fire-prone terrain on the Front Range. Whichever jurisdiction you’re in, confirm which code applies to your address before planning an exterior project. See our full service area list to check whether HRTI covers your community.

What “Class A Fire-Rated” Means for Real Wood Siding

A Class A rating is the highest of three fire-performance ratings assigned under ASTM E84, the standard test method for surface burning characteristics of building materials, meaning a flame-spread index between 0 and 25. Untreated wood siding does not meet this rating on its own; achieving it requires a pressure-impregnated fire-retardant treatment driven into the wood’s cell structure, not a surface-level stain, paint, or char treatment. See our full guide on Class A fire-rated wood siding and which products qualify for a deeper look at how the rating works and which manufacturers offer it.

Worth noting here since it’s part of HRTI’s own siding lineup: Shou Sugi Ban, the Japanese technique of charring cedar planks, does add real fire resistance and a distinctive look, but charring alone is not the same as a wood product tested and certified to a specific Class A flame-spread index. If your project is in a Class 2 WUI zone that requires documented Class A performance, confirm whether the specific charred-wood product you’re considering carries that certification before counting on it to satisfy the code.

Class A Fire-Rated Real Wood Options for Colorado Homes

More than one manufacturer offers real wood siding treated to a Class A rating, and the right choice depends on the look you want, the wood species, the finish, and what your local building department will accept. Three worth knowing:

Montana Timber Products: Fireline

Montana Timber Products, whose wood siding is already part of HRTI’s siding lineup, offers a pressure-treated, fire-retardant process it calls Fireline, which the company states can be added to any of its product lines, including its Ranchwood, AquaFir, and Charwood siding. Montana Timber Products markets Fireline-treated wood as delivering Class A fire-rated protection and Wildland-Urban Interface (WUI) compliance, and describes the treatment as an all-natural, non-toxic formulation that’s pressure-impregnated into the wood rather than applied as a surface coating. Per the manufacturer, the treatment is formulated to last the lifetime of the wood without requiring retreatment.

Vintage Woods: Flame Repel (Made in Gypsum, Colorado)

Vintage Woods is based in Gypsum, in Eagle County, which makes it a Colorado-made option. The Colorado State Forest Service’s forest products directory lists Vintage Woods as a maker of siding and beams, including beetle-kill wood milled to look like reclaimed wood or barnwood. Its fire-rated cladding and trim line, called Flame Repel, is marketed as Class A fire rated and as exceeding both California and WUI fire ratings. The company describes the treatment as a non-toxic formula that is pressure treated for fire resistance through the product’s useful life, and says its Class A products undergo accelerated weathering tests. Vintage Woods’ site doesn’t name the species offered in the Flame Repel line or publish a flame-spread number on that page, so confirm species, finishes, and test documentation directly with the manufacturer.

Hewn: Class A Exterior Cedar

Hewn’s ignition-resistant exterior cedar is a prefinished Western Red Cedar siding treated with a fire-retardant process the company calls Hewn Thermex-FR. Hewn states the treatment delivers a Class A rating under ASTM E84, with a flame-spread index of 25 or less and a smoke-developed index of 45 or less, and cites code evaluation reports (ESR-1159 and ESL-1021) on its site. It’s offered in a range of prefinished colors, from Weathered Grey and Driftwood to Noir and Titanium White. Hewn mills its siding in Oregon, so it’s a premium out-of-state option rather than a Colorado-made one.

A Fourth Path: Cedar Shake & Shingle Bureau Certi-Guard

The Cedar Shake & Shingle Bureau’s Certi-Guard certification is another recognized path, designating independently fire-retardant-treated cedar shakes and shingles for jurisdictions that require that level of protection.

Because code acceptance of any specific product is determined by the local building department rather than the manufacturer, confirm with Jefferson County, Clear Creek County, or whichever jurisdiction has authority over your project that your chosen Class A product satisfies that jurisdiction’s documentation requirements before ordering materials. See our full Siding service page for the full range of materials HRTI installs.

Comparing Material Pathways to a Compliant Exterior Wall

Before You Re-Side or Build New in a Jefferson or Clear Creek County WUI Zone

• Confirm your property’s WUI overlay zone classification (Class 1 vs. Class 2) with your county’s building or planning department.
• Check whether your project triggers compliance. New buildings, additions, re-roofing, deck replacement, and exterior wall work affecting 25 percent or more of your home’s wall area do; painting, staining, routine maintenance, and smaller exterior work generally don’t, since Jefferson County’s code is not retroactive.
• Request manufacturer documentation, such as test reports or product listings, for whichever Class A product you’re considering, and confirm your local building department accepts it for your specific project.
• Plan your defensible space verification separately: it’s handled through a county-approved Wildfire Mitigation Specialist (or, for a re-siding permit in Jefferson County, a homeowner self-inspection), since vegetation management is evaluated independently from the building materials themselves.

How HRTI Helps With Wildfire-Code Siding Projects in Jeffco and Clear Creek County

HRTI installs James Hardie fiber cement, LP SmartSide DiamondKote with RigidStack, vinyl, metal, and specialty wood siding, including Montana Timber, and can help homeowners source premium Class A real wood options like Vintage Woods and Hewn. All of it goes over the correct sheathing, and HRTI can help identify and document materials that meet your property’s specific WUI zone requirements as part of a free estimate.

Frequently Asked Questions

What is the Colorado Wildfire Resiliency Code?

The Colorado Wildfire Resiliency Code is a statewide building code that took effect July 1, 2025, requiring ignition-resistant construction (noncombustible or fire-retardant-treated roofing, siding, decking, vents, and more) for homes in higher-risk Wildland-Urban Interface zones. Local jurisdictions were required to adopt it, or an equivalent, by April 1, 2026, with enforcement that began July 1, 2026.

When did Jefferson County’s updated wildfire code take effect?

July 1, 2026, so it is now in effect. Jefferson County’s Board of County Commissioners approved the updated Wildfire Resiliency Code and WUI overlay map on March 10, 2026. It applies only to unincorporated Jefferson County properties within the WUI overlay district, for new buildings, additions, and qualifying exterior work, and is not retroactive.

Does Clear Creek County require Class A fire-rated siding?

Clear Creek County’s building department lists the 2025 Colorado Wildfire Resiliency Code among its adopted building codes, and that statewide code requires ignition-resistant exterior wall materials, which includes Class A fire-rated wood, in higher-risk WUI zones. Confirm your property’s specific zone classification and any county amendments with Clear Creek County’s Building Department before finalizing material choices.

Can I still use real wood siding under these new codes?

Yes, as long as it’s pressure-treated to a Class A fire rating (a flame-spread index of 0 to 25 under ASTM E84). Manufacturers offering this include Montana Timber Products (Fireline), Vintage Woods in Gypsum, Colorado (Flame Repel), and Hewn (Thermex-FR). Untreated real wood siding does not meet this standard on its own.

Is there a Colorado-made Class A fire-rated wood siding?

Vintage Woods, based in Gypsum, Colorado, markets a Class A fire-rated cladding and trim line called Flame Repel. Confirm species, finishes, and test documentation with the manufacturer, and confirm acceptance with your local building department, before ordering.

Are Class A treated wood products like Fireline, Flame Repel, and Thermex-FR accepted for projects in Jeffco or Clear Creek County?

Each manufacturer markets its product as Class A fire rated, but acceptance of any specific product for a given project is determined by the local building department, not the manufacturer. Confirm acceptance with Jefferson County’s or Clear Creek County’s building department before ordering materials.

Does the new wildfire code apply to homes in Conifer?

Conifer is an unincorporated Jefferson County community, so Jefferson County’s Wildfire Resiliency Code applies to properties that fall within the county’s WUI overlay district, for new buildings, additions, and qualifying exterior work such as re-siding 25 percent or more of the exterior walls. Confirm your address and WUI zone with Jefferson County’s Planning and Zoning or Building Safety staff before choosing materials.

Does the new code apply if I’m only repainting or doing minor repairs?

Generally, no. Jefferson County’s code exempts painting, staining, and similar maintenance or restorative work, as well as exterior wall work affecting less than 25 percent of the wall surface area, and it is not retroactive. Confirm with your local building department whether your specific project counts as a triggering alteration.

HRTI: Windows, Doors, Siding, Painting & Roofing, Done Right, From the Studs Out

HRTI has been a full-service exterior remodeling contractor in the Denver metro area and foothills since 1972. Whatever brought you to this page (a siding repair, a re-roof, new windows, or an exterior paint job), our crews inspect what’s behind the surface (sheathing, flashing, moisture barriers, framing) before we ever touch the finish material, because the finish is only as good as what it’s fastened to.

We install and service:

• Windows & Doors: energy-efficient replacement windows and entry/patio doors from Pella, Sierra Pacific, Simonton, Sunrise, Weathershield, and more
• Siding: James Hardie fiber cement, LP SmartSide DiamondKote with RigidStack, vinyl, metal, and specialty wood siding, installed over the correct sheathing every time
• Exterior Painting: full prep, repair of rotted or damaged substrate, and premium Sherwin-Williams coatings
• Roofing: asphalt shingles, synthetic shingles (including DaVinci slate and shake), stone-coated steel, and Class A fire-rated options like CeDUR synthetic shake

Planning a re-side, re-roof, or new build in a Jefferson or Clear Creek County WUI zone, including Conifer and Evergreen? Call HRTI at 303-984-6159 or email info@hrti.com for a free consultation. You can also reach us anytime through our contact page.

Sources & Further Reading

• HRTI: Jefferson & Clear Creek County Wildfire Resiliency Code (2026)
• Jefferson County: Defensible Space & Wildfire Mitigation
• Colorado Politics: Jeffco Adopts Updates to Wildfire Resiliency Code
• EVstudio: Traversing Colorado’s Wildfire Resiliency Code (CWRC)
• Clear Creek County Building Codes
• Montana Timber Products: Fireline Wood Fire Treatment
• Vintage Woods: Fire-Rated Cladding & Trim
• Colorado State Forest Service: Vintage Woods
• Hewn: Ignition-Resistant Exterior Cedar
• HRTI: Class A Fire-Rated Wood Siding: What It Is and Which Products Qualify
• HRTI Siding Services