Top 5 Roofing Code Changes from 2025 and What to Expect in 2026
As Colorado roofing contractors navigate 2025, several critical code changes are reshaping how projects are planned, inspected, and executed. The Colorado Roofing Association's Building Code & Standards Committee has identified key updates that directly impact project planning, material selection, inspections, and warranty compliance.
This guide summarizes the most important 2025 code changes affecting your business and provides insights into what's coming in 2026.
Understanding 2025 Code Changes: Key Updates from CRA
The CRA Building Code & Standards Committee continues to monitor code adoption across Colorado's 70+ municipalities and builds relationships between roofing professionals and local building departments. In 2025, the most significant impacts come from two critical advisory bulletins addressing underlayment and ventilation requirements.
Change #1: Synthetic Felt Underlayment Requirements
One of the biggest shifts in 2025 involves the materials used for roof underlayments, particularly the transition from traditional asphalt-impregnated felt to synthetic alternatives.
Download the full Synthetic Felt (bulletin).
What's Changing:
Traditional asphalt-impregnated felt has a perm rating of 3.0 to 5.0, classifying it as a Class 3 vapor retarder. This allows moisture to pass through the felt, functioning as a vapor diffuser that helps prevent condensation buildup in attic spaces.
Many synthetic felt underlayments, however, have polypropylene liners with perm ratings of 0.1 or less—meaning they act as vapor barriers rather than vapor diffusers. This fundamental difference changes the dynamics of your roofing system.
Why This Matters:
When you remove asphalt-impregnated felt and install a low-perm synthetic felt without making corresponding system adjustments, you're changing how moisture moves through the roof assembly. If your roof system is not properly vented to meet building code requirements with balanced through-roof ventilation, condensation issues can develop—and you become liable for the resulting damage.
Roofing manufacturers understand this issue and have built it into their warranty requirements. Nearly every shingle manufacturer now requires all roofs to be vented to meet building code requirements in IRC Section 806 (IBC Section 1202.2). Many warranty documents explicitly state that the roof warranty will be voided if proper ventilation is not installed.
How to Approach It:
When specifying synthetic felt underlayments, you have options:
- Choose high-perm synthetic underlayments that function as vapor diffusers rather than vapor barriers. Several synthetic roof underlayments on the market have high perm ratings (greater than 0.50) that help mitigate condensation issues.
- Verify fire classification for the underlayment being used. Ensure it meets the fire classification requirements for the roof system in the specific jurisdiction where work is being performed.
- Communicate with your crew and inspectors about the underlayment choice and its implications for ventilation requirements. When switching from traditional to synthetic felt, make this a conversation point during project planning.
- Document your underlayment selection and confirm it meets local code requirements before installation begins.
Impact on Your Projects: If you've been using traditional asphalt felt for years, this shift requires material education and specification updates. Switching to low-perm synthetic felt without adjusting your ventilation approach can lead to warranty disputes and customer callbacks. This is a material change that affects your standard practices.
Change #2: Steep Slope Roof Ventilation Requirements
The second major 2025 code update focuses on strict ventilation requirements for steep slope roof systems—particularly asphalt shingle roofs. This is not a new requirement, but it's becoming more heavily enforced as manufacturers tighten warranty language.
Download the Steep Slope Roof Ventilation (bulletin).
What the Code Requires:
Building codes reference ventilation requirements in IRC Section 806 and IBC Section 1202.2. These sections specify:
Minimum ventilating area: The net free ventilating area shall be at least 1/150 of the vented space.
Exception option: In Climate Zones 6, 7, and 8 (which includes most of Colorado), the minimum net free ventilation area can be reduced to 1/300 of the vented space IF both of these conditions are met:
- A Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling
- At least 40% and no more than 50% of the required venting area is provided by ventilators located in the upper portion of the attic or rafter space (within 3 feet of the ridge or highest point)
- The balance of required ventilation is provided by eave or cornice vents
Airspace requirement: An airspace of at least 1 inch must be maintained between the insulation and roof sheathing.
Ventilator installation: All ventilators must be installed according to manufacturer's installation instructions.
CRA's Best Practice Recommendation:
Beyond the minimum code requirements, the CRA Building Code & Standards Committee recommends that steep slope roof systems be vented with balanced through ventilation with a variance of no more than 10% between intake and exhaust venting. This means if you need 100 square inches of total ventilation, roughly 45-55 square inches should be intake and 45-55 should be exhaust.
This balanced approach ensures sufficient airflow through roof cavities, reduces the risk of moisture accumulation, and helps prevent warranty voidance.
Why This Matters for Your Business:
Roof ventilation is required on most steep slope systems because:
- It's manufacturer-mandated. Almost every shingle manufacturer includes roof ventilation requirements in their installation instructions, which become part of the building code by reference.
- Warranty language is getting stricter. Manufacturers now include explicit language voiding warranties if proper roof ventilation is not installed with new roofs, recovers, or reroofs.
- Colorado's climate demands it. In Colorado's freeze-thaw cycles and extreme weather, inadequate ventilation accelerates roof deterioration and increases ice dam risk.
- Building departments are enforcing it more strictly. Inspectors are becoming more diligent about verifying that ventilation meets code requirements.
How to Implement:
- Calculate ventilation requirements for each project based on attic space and your jurisdiction's adopted code
- Design for balance with roughly equal intake and exhaust ventilation
- Plan ventilation during the initial bid and design phase rather than as an afterthought
- Educate homeowners that proper ventilation is a code requirement, not an optional upgrade
- Document your ventilation design and keep records showing compliance with code and manufacturer requirements
- Follow manufacturer installation instructions for all ventilation products
Impact on Your Projects: If you've been installing roofs with minimal or one-sided ventilation, 2025 is the year to reassess your standard practices. Building departments are enforcing this more strictly, and manufacturer warranty requirements are increasingly strict. Projects that don't meet ventilation code requirements are at risk for warranty disputes and customer problems.
Changes #3-5: What Else Shifted in 2025
Beyond the synthetic felt and ventilation bulletins, 2025 brought other important considerations:
Change #3: 2021 I-Code Adoption Across Jurisdictions
Colorado is in the middle of a staggered code adoption cycle. Effective January 1, 2025, the 2021 International Building Codes came into effect in multiple Colorado jurisdictions. Additionally, Boulder County announced it is updating from the 2015 I-Codes to the 2021 I-Codes, with adoption anticipated early in 2025.
What this means: You may be working in different jurisdictions with different code versions (some still on 2018, some on 2021). Always verify which code version your specific project location has adopted. Use CRA's partnership with OneClick Code to pull jurisdiction-specific building code information for each project address.
Change #4: Updated Virtual Inspection Procedures
Some municipalities are updating inspection procedures for efficiency. For example, Thornton has implemented new inspection protocols including mid-roof inspections conducted via drone photos and virtual final inspections. Some low-slope roofs now require system warranty uploads for final inspection approval.
What this means: Check with your local building department about inspection procedures. Remote inspections require clear documentation and photos. Have your warranty paperwork organized and ready for upload before scheduling final inspection.
Change #5: Building Departments Enforcing Existing Code More Strictly
While not new code, building departments are cracking down on enforcement of existing requirements, particularly around:
- Proper underlayment selection and installation
- Moisture control and ventilation
- Two-layer maximum roofing restrictions
- Roof board spacing requirements (no continuous openings over half-inch)
What this means: If your crews have been using workarounds or taking shortcuts, 2025 is the time to tighten up standard practices and ensure full compliance with building codes.
Planning for 2026: What to Expect
As we look ahead to 2026, the CRA Building Code & Standards Committee is monitoring several trends:
Energy efficiency updates: Expect continued focus on energy codes, with potential updates tied to energy efficiency and green building practices.
Material requirements: As synthetic materials become more prevalent, manufacturers will likely update requirements around perm ratings, fire classification, and performance standards.
Climate-specific standards: Colorado's extreme weather continues to drive more rigorous standards around moisture control, ventilation, and seasonal considerations.
Building department coordination: The CRA will continue advocating for consistent enforcement across municipalities and working to align code interpretation with industry best practices.
How Code Changes Impact Your Daily Work
Understanding 2025 code changes affects multiple aspects of your business:
Project Planning:
- Start every bid by verifying which code version applies to the project location
- Factor ventilation requirements into your material estimates and labor costs
- Specify underlayment perm ratings and ensure compatibility with ventilation design
- Document your code compliance strategy in the contract
Inspections:
- Prepare inspection documentation before the site visit
- Have photos of ventilation installation, underlayment choice, and airspace compliance
- Be ready to explain your ventilation design and how it meets the adopted code
- Keep copies of manufacturer installation instructions on site
Materials:
- Review your standard material specifications, particularly underlayments
- Confirm that synthetic felt options meet high-perm requirements or plan for additional ventilation
- Verify fire classification meets local code
- Stock materials that align with current code requirements in your primary markets
Warranty Compliance:
- Understand manufacturer warranty requirements around ventilation and underlayment
- Ensure your installation practices meet warranty conditions
- Keep detailed records of materials used and installation procedures
- Communicate warranty requirements to customers upfront
Resources for Staying Current
The CRA Building Code & Standards Committee provides several resources to help you stay on top of code changes:
CRA Code Bulletins: The committee publishes advisory bulletins on emerging code issues. The 2025 bulletins on Synthetic Felt and Steep Slope Roof Ventilation are essential reading for all members.
OneClick Code Partnership: CRA members have unlimited free access to OneClick Code snapshots for any project address in Colorado. This tool automatically pulls the correct jurisdiction, building standards, code version, permit fees, and manufacturer specifications for each project—saving you time and ensuring accuracy.
Direct Communication: If you have questions about code interpretation in your jurisdiction, contact your local building department or contact the CRA for guidance.
Ready to Stay Compliant?
Download CRA's 2025 Code Update Bulletins for detailed guidance on synthetic felt underlayments and steep slope roof ventilation requirements. These bulletins are prepared by the CRA's Building Code & Standards Committee and provide the specific code references and best practices you need.
Access Code Updates & Bulletins
For additional code resources, CRA members can also access the OneClick Code tool at no cost to pull jurisdiction-specific building code information for every project address.
Questions about code compliance in your area? Reach out to the CRA Building Code & Standards Committee or contact your local building department for clarification.