2024 I-Codes Adoption Kit

Building codes are adopted at the state or local community level. During their code adoption processes, there are typically questions related to new changes in the codes and the cost impact of the code editions being considered for adoption. This kit addresses these questions relative to adoption of the 2024 I-Codes and provides NAHB-suggested amendments that reflect concerns from builders, including practicality, cost-effectiveness, and payback for home buyers.

The 2024 I-Codes Adoption Kit consists of three parts:

• Significant changes made in the 2024 I-Codes relative to the 2021 editions. One section covers changes in the International Residential Code (IRC) for single-family construction and one covers changes in the International Building Code (IBC) and associated codes affecting multifamily construction.
• Cost impacts of adopting the 2024 IRC relative to the 2021 edition.
• NAHB-suggested amendments to improve the codes’ practicality and cost effectiveness.

Significant Changes to the 2024 International Residential Code (IRC)

This summary includes significant changes to the International Residential Code (IRC) building provisions (Chapters 1-10 and 44), electrical, mechanical, and plumbing provisions (Chapters 12-43) and appendices. Changes to the energy efficiency provisions (Chapter 11) are addressed as part of a separate 2024 IECC Adoption Kit. This is not all the changes that were approved. Download the Significant Changes to the 2024 IRC, for a list of significant changes, which include the following:

• IRC Section R401.4.1 Geotechnical evaluation: The existing soil classifications table is moved to a more logical location and expanded to allow the use of USDA data and textural descriptions to ensure builders select a proper soil classification in lieu of obtaining a geotechnical investigation.
• IRC Section R502.11 Floor framing supporting guards: Prescriptive options area added for framing at the open edge of a floor supporting a required guard assembly. Prescriptive options are included for conventional and timber edge framing. Floor trusses and I joists used as edge members supporting guards shall specifically consider the guard loads in their design.
• IRC Section R506.3.3 Vapor retarder: A 6-mil construction-grade polyethylene vapor retarder is allowed to be placed under a concrete floor slab instead of a 10-mil vapor retarder complying with ASTM E1745 Class A requirements. This reverses the change from last cycle requiring the 10-mil proprietary vapor retarder under floor slabs.
• IRC Section R703.7.3.1 Dry climates. For stucco installations in dry climates, the use of a material tested for minimum drainage efficiency over one layer of 60-minute Grade D paper or ASTM E2556 Type II-compliant water-resistive barrier material is allowed as an option. For homes that do not require continuous foam plastic insulating sheathing to meet energy codes, this could provide a cost-effective alternative to a furred drainage space.
• Appendix BO Existing Buildings and Structures: Appendix AJ Existing Buildings and Structures is relocated to Appendix BO and extensively revised to address structural requirements for work on existing buildings. Existing sections on repairs and alterations are revised and expanded and new sections on additions and relocated buildings are added. Certain addition or alteration projects may require hiring a structural engineer, in addition to any needed structural upgrades.

Significant Changes to the 2024 International Building Code (IBC) and related codes for Multifamily

This summary includes changes to the International Building Code (IBC), International Energy Conservation Code (IECC), International Existing Building Code (IEBC), International Fire Code (IFC), International Mechanical Code (IMC), International Plumbing Code (IPC), and International Wildland-Urban Interface Code (IWUIC). This is not all the changes that were approved. Download the 2024 Significant Changes for Multifamily, for a list of significant changes, which include the following:

• IBC Section 903.3.1.2.3 [IFC 903.3.1.2] NFPA 13R sprinkler systems. For Group R-2 buildings, NFPA 13R systems can be used where the highest point of the roof assembly is not more than 45 feet above the lowest level of fire department access. This restores the ability to use NFPA 13R systems in many four-story multifamily buildings instead of full NFPA 13 systems, partially reversing what a change in the 2021 IFC effectively required.
• IBC Section 1107.2 Electrical vehicle charging stations. The provisions for electrical vehicle (EV) charging stations were modified so R-2 occupancies are no longer exempt. At least one charging station and up to 5% of such spaces provided for use by residents will now need to be accessible. The change could result in an equal number of accessible EV spaces and accessible standard spaces needing to be provided. R-3 and R-4 are still exempt.
• IBC Section 1110.6 Laundry equipment. A minimum number of washers and dryers in a common laundry room are now required to be accessible in all cases, instead of being adoptable via an appendix. This exceeds Federal law as the Americans with Disabilities Act does not require the shared areas of multifamily buildings to comply; Fair Housing Act accessibility requirements only require accessible washers/dryers in an accessible dwelling unit.
• IEBC Section 306.6 Additions. The accessibility provisions for existing buildings are modified so only the number of dwelling or sleeping units added to an existing building are required to meet accessibility requirements. This correlates the IEBC with FHA accessibility guidelines.
• IWUIC Section 504.10 and 505.10 Vents. Roof, attic, foundation, and underfloor vents in Ignition-Resistant Class 1 and 2 construction must either be a listed vent product tested to ASTM E2886 or be non-combustible corrosion-resistant mesh with a maximum 1/8-inch mesh spacing. Listed products are not available for all types of attic and foundation vents and more expensive than aluminum or steel mesh, and either way larger or more vents may be required due to reduced net free area.

Cost Impact for Adoption of the 2024 I-Codes

A report on the Estimated Costs of the 2024 IRC Code Changes by Home Innovation Research Labs has determined the cost impact for typical new homes ranges from essentially no impact to a $2,200 savings relative to the 2021 International Residential Code (IRC) for provisions not related to energy efficiency or to additions and substantial alterations to existing homes. These typical values will vary based on the climate zone and house configuration. See the full 2024 IRC Cost Study.

A Home Innovation study on the 2024 International Energy Conservation Code and IRC Chapter 11 is in progress and will be available later this year, as will an addendum to the Estimated Costs of the 2024 IRC Code Changes that will quantify the cost impact of additions and substantial alterations.

Suggested Amendments

NAHB has prepared recommendations for amending the 2024 International Residential Code, and other 2024 ICC model codes. Each recommended amendment is provided in a draft form that includes the code section and text to be amended in legislative format (underline and strikeout), a reason statement, and an NAHB staff contact.

Each suggested amendment should be considered individually to ensure that it is an improvement for the jurisdiction. Priorities can differ from region to region, and HBAs should not hesitate to consider alternative code text that may be more appropriate (Word version of the document is provided). If there are any questions on the change or the HBA is looking for assistance on modifying the amendment, please contact NAHB staff for assistance.

Suggested Amendments to the 2024 I-Codes (PDF)

Suggested Amendments to the 2024 I-Codes (Microsoft Word)

For Chapter 11 of the IRC, see the suggested amendments to the residential chapter of the IECC on the International Energy Conservation Code webpage.

Related Resources

Fire sprinkler requirements for one and two-family homes continue to be part of the International Residential Code, despite significant consumer resistance and debunked claims to their necessity. NAHB’s Fire Sprinkler resource page remains an excellent resource for removing these requirements.

In addition, resources on energy and arc fault interrupters can be found on the Energy Codes page and the Arc-Fault Circuit Interrupters information page.