IRC R317 - Garages and Carports: The IRC's Consolidated Garage Requirements

Garages have their own IRC chapter. In the 2024 edition of the International Residential Code, Section R317 is the home for consolidated garage requirements. Earlier IRC editions (2021 and prior) used Section R309 for the same content.

What this section says

IRC 2024 R317 addresses several aspects of garage construction and equipment. Key provisions include the following.

Floor surface. Garage floors must be of approved noncombustible material. This means concrete for virtually all residential garages.

Floor drainage. The floor must drain to outside the building or to an approved interior drainage system. Flat garage floors that allow water to pool near the house-garage door are common code deficiencies.

Fire separation. R317 incorporates the fire separation requirements of R302.6 (wall and ceiling drywall assemblies) and R302.5 (the fire-rated door between the garage and the house). These cross-references make R317 the starting point for understanding all garage-to-house requirements.

Carbon monoxide alarms. When a garage is attached to a dwelling, the dwelling must have CO alarms as required by the applicable CO provisions in R315. An attached garage is a primary source of CO risk in residential construction.

Automatic door openers. R317 includes the requirement (formerly at R309.4) that automatic garage door openers be listed and labeled in accordance with UL 325. This is the code's hook to the safety standard.

The IRC's technical article summarizes the intent:

"Section R309.4 requires automatic garage door openers to be listed and labeled to UL 325."

When it applies

R317 applies to attached and detached garages that are part of or accessory to a dwelling regulated by the IRC. It applies wherever the 2024 IRC has been adopted.

Denver's 2025 Building Code is based on IRC 2024. Jefferson County, Larimer County, and most other Front Range jurisdictions have also adopted recent IRC editions. Check with the local AHJ for the specific edition in effect and any local amendments.

Contractors and homeowners pulling permits for garage work in Denver will be reviewed against the 2025 DBC, which incorporates the R317 requirements.

What this means for you

Know your edition. Some jurisdictions still enforce an older IRC edition. The section number for garages may be R309 rather than R317. The content is similar, but the section number matters when communicating with an inspector.

The opener requirement is here. The UL 325 listing requirement for automatic openers is part of R317. If an opener is not UL-listed, it fails this section. Inspectors in Denver check for the UL mark.

CO protection is mandatory. An attached garage means the adjacent dwelling needs CO alarms. If your renovation includes an attached garage, confirm CO alarm placement meets R315 requirements.

Fire separation applies. The separation requirements of R302.5 and R302.6 are referenced by R317. The garage-to-house door and the drywall assembly are both covered.

G Brothers installs only UL 325-listed openers and notes compliance with R317 requirements when permits are involved.

Full text and source

Read the full 2024 IRC Chapter 3 at https://codes.iccsafe.org/content/IRC2024P2/chapter-3-building-planning. The Denver 2025 Building Code is available at denvergov.org.

IRC R317 is a model code provision. It applies only in jurisdictions that have adopted it. Confirm the adopted edition and any local amendments with your AHJ.