What ember-resistant sealing do Colorado WUI garage doors need?

The 2025 Colorado Wildfire Resiliency Code (CWRC) added specific garage door requirements for properties in Moderate or High Fire Intensity zones (shown in orange and red on the CWRC map, sometimes informally called Orange and Red zones). The requirements target one specific risk: windblown embers entering the garage through gaps around the door. If your property is in a Moderate or High Fire Intensity zone and you pull a permit for new construction or a large addition, your garage door must meet these standards. This page covers the three compliance methods, the gap dimension that triggers requirements, and how to find out which zone your property is in.

What is the maximum allowable gap for a garage door in a Colorado WUI zone?

The CWRC sets a maximum allowable gap of 1/8 inch between the garage door and the door opening on all four sides. This applies to Moderate and High Fire Intensity areas (Class 2 zones under the CWRC), which carry higher fire intensity risk under Colorado's WUI mapping.

The 1/8-inch rule is based on ember transport research. Burning embers can pass through gaps larger than about 1/8 inch and ignite materials inside. The garage is a high-priority target in wildfire defense. It typically holds fuel (vehicle fluids, stored materials, insulation) and connects directly to the living space in most Front Range homes. An ember that enters through the garage door gap can start an interior fire even when the exterior of the home looks undamaged.

This requirement applies when you pull a permit for new construction or for additions of 500 square feet or more. A like-for-like garage door replacement on an existing structure does not trigger CWRC requirements unless you are also pulling a permit for another qualifying project at the same address.

What are the three ways to comply with the ember-sealing requirement?

The CWRC allows three methods to achieve compliant sealing on a garage door:

Method 1: Ember-resistant weather-stripping. The weather-stripping on all four sides of the door must be rated for ember resistance. The material must meet specific flammability and durability standards set by the CWRC. The Colorado DFPC maintains a tested and approved materials list on its CWRC testing requirements page. Standard residential vinyl weather-stripping does not qualify. Look for products listed in the DFPC materials database, and verify any product against the current DFPC approved materials list before specifying it.

Method 2: Door overlap onto jambs and headers. The garage door can be configured to overlap the door jambs and header. This closes the gap without depending on the weather-stripping material. It works when the door panel extends slightly past the rough opening edges. Some steel sectional doors support this overlap configuration; others do not. Check with the door manufacturer before specifying this approach.

Method 3: Metal flashing on jambs and headers. Aluminum or galvanized steel flashing installed on the jambs and header creates a non-combustible barrier at the gap. The flashing covers the joint between the door frame and the surrounding wall, blocking the path embers would take. This method works with standard doors and does not depend on specific door product features.

Any of the three methods meets the code. Many contractors combine approaches. Ember-resistant weather-stripping plus metal flashing together gives more redundancy than either alone. The DFPC requires only that the 1/8-inch gap standard is met, not a specific combination.

Which Colorado Front Range counties have WUI zones that trigger these requirements?

The WUI designation is made at the state level using Colorado's fire risk modeling. The CWRC map identifies Moderate Fire Intensity (orange on the map), High Fire Intensity (red), Low Fire Intensity (yellow), and undesignated areas. CWRC Class 2 requirements (which include the garage door sealing requirement) apply to Moderate and High intensity areas. Several Front Range counties have significant Moderate or High Fire Intensity acreage:

Jefferson County has Moderate and High intensity areas across the foothills communities: Evergreen, Conifer, Morrison, Genesee, and Indian Hills. Parts of Lakewood and Wheat Ridge that border open space may also be included.

Boulder County has Moderate and High intensity areas in the mountain communities west of Boulder. Gold Hill, Sunshine Canyon, and Fourmile Canyon are examples. Unincorporated areas at the urban-wildland edge are also commonly designated.

Douglas County has Moderate intensity areas in the western portions. Communities along CO-126, parts of Castle Rock near the escarpment, and unincorporated areas toward Perry Park are among them.

El Paso County has Moderate and High intensity areas in the Black Forest region and the foothills communities west of Colorado Springs.

Larimer County has Moderate and High intensity areas in the mountains west of Fort Collins and in the Estes Park corridor.

Within cities, WUI zone status is set at the parcel level, not the city level. A house in Evergreen may be in a Moderate or High intensity area while a neighbor two blocks away is not. The Colorado Division of Fire Prevention and Control maintains the official WUI zone lookup at the DFPC website. You can enter your address there and get your zone classification directly.

Method	How it works	Works with standard doors
Ember-resistant weather-stripping	DFPC-listed material on all 4 sides	Yes, if correct product used
Door overlap onto jambs/headers	Door panel extends past opening edges	Depends on door model
Metal flashing on jambs/headers	Non-combustible barrier at gap	Yes, added at installation

When do the requirements apply to existing homes?

The CWRC does not retroactively require existing homes to retrofit garage doors for ember resistance. Homes that are not under an active building permit are not required to comply.

The requirement triggers in three situations:

1. New construction. Any new home or garage built in a Moderate or High Fire Intensity WUI area must comply with the CWRC. This includes the garage door ember-sealing requirement.

2. Additions of 500 square feet or more. If you add a room addition, second garage bay, or attached structure of 500 sq ft or more, the garage door must come into CWRC compliance.

3. Any permitted work in some jurisdictions. Some local jurisdictions adopted the CWRC with amendments that expand the trigger to any permitted work, not just large additions. Check with your local building department before assuming the 500 sq ft threshold is the only trigger.

Even if you are not required to comply, adding ember-resistant weather-stripping to an existing garage door in a fire-prone area is a low-cost protection step. A standard double garage door has roughly 30 linear feet of perimeter. Ember-resistant weather-stripping on all four sides of that perimeter closes the gap that standard vinyl misses in fire conditions. Annual inspection is good practice. Weather-stripping that is cracked, compressed flat, or missing leaves gaps that embers use.

G Brothers Garage Doors installs CWRC-compliant garage doors and ember-resistant sealing systems throughout Jefferson County, Boulder County, Douglas County, and the broader Front Range. We know the local WUI zone maps and the permit process in each jurisdiction. Free estimates, same-day service on most projects.

A practical note on timing: if you are planning any permitted project in a WUI Moderate or High Fire Intensity area, address the garage door compliance before pulling the permit, not after. Some building departments require the garage door compliance plan as part of the permit submittal. Adding it after the permit is approved can require a plan revision and add time to the project. The most efficient path is to confirm your WUI zone status, choose a compliant door and sealing method, and include that in the original permit application.

If your garage door is already in good condition and just needs upgraded weather-stripping, that work can often be done quickly without disrupting your schedule. The material cost for ember-resistant perimeter weather-stripping on a standard two-car door is modest. Labor is a few hours. It is one of the lower-cost wildfire hardening steps available to Front Range homeowners.