The code is not retroactive, so an untouched existing roof is left alone. But if a home in a mapped WUI area has its roof covering replaced, or has 25% or more of the roof surface area replaced, or has work done that effectively replaces the covering, then the entire roof covering must be brought up to new-construction requirements: Class A rating, ember-space protection and compliant valley flashing. The only exception is a covering that already complies.
What the trigger actually says
Section 101.6 is the provision that matters most to homeowners. It converts what feels like a repair decision into a whole-roof decision once you cross the threshold. Three things trip it:
- Replacing the roof covering, at any size.
- Replacing 25% or more of the roof surface area.
- Work that effectively replaces the covering, even if it is described as repair.
What that means for scope and cost
A small repair under 25% of the roof does not trigger the whole-roof requirement. Crossing that threshold, or doing any full reroof, means the whole covering has to be Class A and WUI-compliant, with ember-space protection where the covering profile creates a gap, and valley flashing of at least 0.019 inch corrosion-resistant metal over a 36-inch-wide cap sheet running the full valley length.
This can change project scope and price, and it is the single biggest source of surprise on a wildfire-area roof. The most useful thing a roofer can do is answer the 25% question in writing, in the bid, before anyone commits. We do that on every WUI-area estimate.
The wall trigger that often rides along
Section 101.7 sets a parallel 25% trigger for exterior walls. Replacing 25% or more of exterior wall surface triggers compliant wall materials and requires the 0 to 5 foot zone around the structure to be brought into defensible-space compliance. Reroof and residing work often bundle, so it is worth knowing before you scope both at once.
Work the code exempts
Section 102.10 lists work outside the code's reach. It includes:
- Interior alterations.
- Additions that add less than 500 square feet of footprint. At 500 square feet or more, Section 101.5 requires the addition to meet new-construction requirements.
- Roof work affecting less than 25% of the surface.
- Exterior wall work under 25%.
- Painting and similar maintenance.
- Detached sheds under 120 square feet located 10 or more feet from occupiable structures.
- 35-acre parcels with a single residential structure not abutting a residential or commercial area.
Permits, inspections and grandfathering
Reroof permits are required in typical jurisdictions. Where a jurisdiction adopted the code's appendices, there are added permit application, plan review and staged inspection requirements, and the structure must stay accessible for inspection until approved. Some jurisdictions, Eagle County among them, require a wildfire hazard rating on the permit.
Existing legal roofs are grandfathered until a triggering event. There is no forced retrofit of an untouched roof under this code. Separately, some jurisdictions banned wood roofs outright with their own replacement deadlines.
What to demand in a bid
Ask any contractor bidding wildfire-area work for four things in writing: whether the project crosses the 25% threshold, what Class A assembly they are installing and whether it is stand-alone or by-assembly, what vents and valley metal are included, and copies of the manufacturer's listed assembly documentation for your insurance file.
Requirements vary by jurisdiction
Colorado's wildfire code is a state minimum, but adoption and enforcement happen locally, and adoption is uneven. Some counties, towns and fire districts adopted the code, some adopted amended or more stringent versions, and some declined. Nothing on this page tells you what applies to your specific address. We confirm the current adopted code and map with your building department before every project in a wildfire area, and we put the answer in writing with the estimate.
Common questions
- What is the 25% roof rule in Colorado?
- In a mapped WUI area, replacing the roof covering or replacing 25% or more of the roof surface area requires the entire roof covering to meet new-construction requirements: Class A rating, ember-space protection and compliant valley flashing.
- Do I have to replace my whole roof if I only repair part of it?
- Not if the work stays under 25% of the roof surface and does not effectively replace the covering. Once you cross 25%, the whole covering has to meet the new-construction standard.
- Is the Colorado wildfire code retroactive?
- No. A home legally standing before adoption may continue as-is. The requirements attach when you do triggering work, such as a reroof or a repair crossing 25% of the roof surface.
Talk to us about your roof
We work out of 9822 Titan Park Cir, Littleton, and cover the Front Range foothills where this code matters most. Call (303) 738-1032 or book an inspection and we will confirm the local requirements, walk the roof, and put the 25% answer in writing with your estimate. Our neighborhood guides and service areas show where we work, and the insurance claim guide covers the documentation side.