How Jurisdictions Adopt the IRC 2024 and Why Your State May Be on an Older Edition

Quick Answer

The IRC is a model code published by the International Code Council every three years. It does not have the force of law anywhere until a state legislature or local governing body formally adopts it through legislation or ordinance. As of 2026, most states have adopted some edition of the IRC, but the edition in effect varies widely—some states are on IRC 2024, others on IRC 2021 or IRC 2018.

Under IRC 2024, some states adopt the IRC at the state level with amendments; others leave adoption to individual cities and counties. California, New York City, and a few other jurisdictions use proprietary codes entirely. Knowing which code edition governs in your specific jurisdiction is a prerequisite to every code compliance question.

What IRC 2024 Actually Requires

Section R101.1 of the IRC 2024 establishes that the code shall be known as the International Residential Code for One- and Two-Family Dwellings and, as such, is the legal title that a jurisdiction adopts when it enacts the code into law. The title provision is not a substantive requirement—it identifies what is being adopted and what it shall be called once adopted. The substance of what is required in any jurisdiction is a product of: the edition of the IRC that was adopted; the local amendments appended to that adoption; and any state supplement documents that modify the base IRC for state-specific conditions.

The IRC publication cycle produces a new edition every three years, with editions designated by the year of publication: IRC 2006, IRC 2009, IRC 2012, IRC 2015, IRC 2018, IRC 2021, and IRC 2024. Each new edition incorporates code change proposals submitted by industry, government, and other stakeholders through the ICC code development process. Changes are debated at public hearings and voted on by governmental members of the ICC. The resulting new edition includes both substantive changes to technical requirements and administrative changes to how requirements are structured and cross-referenced.

Once an edition is published, the ICC makes it available for adoption. States and local jurisdictions then go through their own legislative and regulatory processes to formally adopt the new edition. This process typically takes two to five years from publication, which means there is almost always a lag between the publication of a new IRC edition and its widespread adoption. IRC 2024 was published in 2023 and is just beginning to be adopted by leading-edge jurisdictions in 2025 and 2026. Most jurisdictions will still be on IRC 2021 or IRC 2018 for several years.

When a jurisdiction adopts the IRC, it typically also publishes a local amendment document that modifies specific IRC provisions for local conditions. Amendments may add requirements (such as hurricane strapping in coastal areas or seismic bracing in high-seismic zones), reduce requirements (such as allowing smaller setbacks in dense urban areas), or replace IRC provisions entirely with locally developed standards. The adopted IRC plus the local amendment document together constitute the locally applicable code. Contractors and designers must have both documents to understand what the local code requires.

Why This Rule Exists

The federated adoption system for model codes reflects the constitutional structure of the United States, where land use and building regulation is primarily a state and local government function. The federal government does not have authority to mandate building codes for private residential construction. The model code system allows the ICC to invest in the expert-led code development process and produce technically sophisticated model codes that states and localities can adopt wholesale or with modifications, rather than each jurisdiction developing its own complete code from scratch.

The amendment system allows the model code to be tailored to local conditions that the national model does not address with sufficient specificity. A building code that works in the mild climate of the Pacific Northwest is not automatically appropriate for the hurricane coast of Florida or the seismic zone of the Pacific Coast. State and local amendments allow the technically sophisticated base code to be adapted to local climate, geology, and demographic conditions without undermining the core structural and life safety provisions that are common across all regions.

The lag between ICC publication and local adoption serves a practical function: it gives the construction industry, plan reviewers, and inspectors time to be trained on the new requirements before they go into effect locally. A code that takes effect without industry training creates compliance problems even among well-intentioned contractors. The adoption lag allows industry training programs, continuing education courses, and updated reference materials to be developed and deployed before the new edition governs actual construction.

What the Inspector Checks at Rough and Final

Inspectors are trained on and enforce the edition of the code adopted in their jurisdiction, not the most recently published edition. An inspector in a jurisdiction that has adopted IRC 2021 applies IRC 2021 at all inspections, regardless of whether IRC 2024 has been published and adopted elsewhere. The edition applicable to a specific project is the edition that was in effect when the permit was issued. A project permitted under IRC 2021 is completed under IRC 2021 even if the local jurisdiction adopts IRC 2024 during the construction period.

At plan review, the plan examiner verifies which edition of the code governs the permit application and reviews the drawings and specifications against that edition. Applications submitted citing a code section that does not exist in the locally adopted edition will be rejected or corrected. Contractors and designers who work across multiple jurisdictions must track which edition governs each project to avoid citing inapplicable code sections in permit submittals.

The certificate of occupancy issued at project completion documents the edition of the code under which the permit was issued, per IRC R110.3. This documentation is part of the permanent property record and is relevant to future code compliance questions when the building is altered or sold. A 2022-permitted project completed under IRC 2021 is permanently identified in its permit record as an IRC 2021 project.

What Contractors Need to Know

Contractors working in multiple states or across a metropolitan area that spans multiple jurisdictions must maintain a per-project record of the applicable code edition and any local amendments. Using IRC 2024 tables and requirements on a project in a jurisdiction that has adopted IRC 2018 is a recipe for plan review rejections and inspection failures. Maintain a jurisdiction reference file that documents the adopted edition and amendment document for each jurisdiction where you regularly work, and update it whenever a jurisdiction announces a code edition change.

Code adoption transitions are a common source of confusion and disputes. When a jurisdiction announces that it is transitioning from IRC 2021 to IRC 2024 on a specific date, projects submitted before that date are governed by IRC 2021 and projects submitted after are governed by IRC 2024. Projects in the middle of plan review at the transition date are typically governed by whichever edition was in effect when the application was submitted, though some jurisdictions give applicants the option to switch to the new edition. Clarify with the building department the treatment of applications in review at the transition date to avoid mid-project surprises.

State supplement documents are as legally binding as the base code. A state energy supplement that requires higher insulation R-values than the base IRC energy provisions is not optional—it replaces the base IRC provision entirely in that state. California’s Title 24 energy requirements, for example, are far more stringent than the IRC energy provisions and completely govern energy compliance for California residential construction. Understanding that local amendments and state supplements can be more, not less, stringent than the base IRC is essential for accurate cost estimating and specification writing.

What Homeowners Get Wrong

Homeowners frequently assume that the most current IRC publication is the code that applies to their project. In most of the United States, it is not. If your state adopted IRC 2021 three years ago and has not yet enacted IRC 2024, IRC 2021 governs your project regardless of what the 2024 edition says. When researching code requirements online, verify that the source is citing the edition applicable to your jurisdiction. Many online code references cite the current ICC publication without clarifying that local adoption may differ.

A related error is assuming that code requirements are uniform across state lines. A deck that complies with the code in one state may not comply in an adjacent state that has adopted a different edition or has local amendments. Contractors who frequently work near state borders must be aware of the adoption differences and not assume that what was approved on the last project in an adjacent jurisdiction will be approved on the current project.

Homeowners in states that have not adopted any model code, or in unincorporated rural areas without a building department, are sometimes surprised to discover that they have no code compliance obligation for residential construction. While this may seem like an advantage in the short term, it creates real problems when the property is sold, financed, or insured. Lenders and insurers often require evidence of code compliance regardless of whether a local code was legally required. Building to at least the standard of the most recently adopted statewide IRC edition is good practice even where no code is technically mandated.

State and Local Amendments

California publishes the California Residential Code (CRC) every three years, aligned with but not identical to the base IRC. The CRC incorporates California-specific amendments for seismic design, fire-resistive construction in wildland-urban interface zones, and Title 24 energy and water efficiency. As of 2026, California is in the process of adopting its 2025 edition of the CRC, which is based on IRC 2024 with California amendments.

Florida adopted the Florida Building Code, 8th Edition in 2023, which is based on IRC 2021 with Florida-specific amendments for hurricane wind design, high-velocity hurricane zone requirements in Miami-Dade and Broward counties, and elevated construction in coastal flood zones. Florida’s amendment process is extensive and the Florida Building Code diverges from the base IRC in significant technical areas.

Texas allows but does not mandate statewide adoption of a residential building code. Many Texas cities have adopted a version of the IRC, but unincorporated county areas and many smaller municipalities have no building code. The Texas Legislature periodically considers statewide code adoption legislation, but as of 2026 no uniform statewide residential code exists outside of city and county adoption.

To find which edition of the IRC has been adopted in your specific jurisdiction, contact your city or county building department directly, check the ICC’s code adoption map at iccsafe.org, or consult your state building codes office. The answer will often include not just the edition but also the list of local amendments that modify the base edition in your jurisdiction.

When to Hire a Professional

For projects spanning multiple jurisdictions—a developer building townhouse communities in several cities, or a contractor licensed across multiple states—engaging a code consultant or permit expediter familiar with each jurisdiction’s adopted code and amendment documents is efficient and reduces compliance risk. Code consultants maintain current adoption databases and can quickly confirm the applicable code for any project location, identify the key differences between the base IRC and local amendments that affect the specific project type, and prepare jurisdiction-specific specification sections for permit submittals.

When a new edition of the IRC is being adopted in your primary jurisdiction and you need to understand what is changing, attending the ICC’s code adoption public hearings, reading the ICC’s published “What’s New” summary for the new edition, and attending continuing education courses on the new edition is strongly recommended. Local code training events hosted by the building department or local building industry associations are one of the most efficient ways to learn what is changing and what the building department will be looking for when the new edition takes effect.

Homeowners planning major renovation projects or ADU additions should have a pre-application meeting with the building department to confirm the applicable code edition, understand what permits will be required, and identify any known local amendments that apply to their project type. This meeting is typically free and can prevent costly design revisions that arise from incorrect code assumptions in the design process.

Common Violations Found at Inspection

• Permit application citing IRC 2024 code sections in a jurisdiction that has adopted IRC 2021, resulting in plan review corrections to conform the application to the locally adopted edition.
• Construction complying with the base IRC but not the local amendment document, discovered at inspection when the inspector applies the local amendment requirement that the contractor was unaware of.
• Energy compliance documentation citing a base IRC energy requirement that has been replaced by a more stringent state energy supplement, resulting in plan review rejection for non-compliant insulation R-values or window U-factors.
• Hurricane strapping requirements from local Florida Building Code amendments not installed on a project by a contractor who used base IRC framing requirements from an out-of-state reference.
• Seismic hold-down hardware missing from a project in a high-seismic-zone jurisdiction whose local amendments require engineered hold-down designs not required by the base IRC prescriptive tables.
• Project permitted under IRC 2021 in a jurisdiction that transitioned to IRC 2024 mid-project, with the contractor incorrectly applying IRC 2024 requirements to work not covered by the new edition.
• Wildland-urban interface fire-resistive siding requirements from a California local amendment not applied because the contractor used base IRC siding specifications.
• ADU project submitted without recognizing that the local jurisdiction has adopted an ADU-specific amendment that imposes different setback, height, and coverage requirements than the base IRC accessory structure provisions.