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Which Building Code Does Your State Use? Residential Codes by State

Almost every residential building code in the U.S. starts from the same book, the International Residential Code (IRC). What changes at the state line is which edition is in force and whether it applies everywhere. 39 states and D.C. adopt a residential code at the state level (in some, it applies only where a town enforces it, or only in certain areas); the other 11 leave it to cities and counties. Here’s the code for one- and two-family homes in every state, with the agency and the rule that adopts it.

Quick answer

Most states use a version of the International Residential Code for houses, most often the 2021 edition. Some apply it statewide with no local changes, some set it as a minimum that towns can tighten, and some leave adoption to local governments. Your local building department enforces it and can tell you the exact edition and amendments for your address. Find your state below.

39states with a state-level residential code

10on the 2024 IRC

15on the 2021 IRC

11states that leave it to local codes

What the residential code covers outside the house

The IRC isn’t just framing and wiring. It sets the rules for a lot of outdoor work, which is why the edition matters when you plan a deck, steps or a wall:

Footings have to reach below the local frost line (see frost line depth by state).
Decks have their own section on footings, ledger attachment, joist spans and guards.
Stairs and guards: riser height, tread depth, handrails and guard height on raised decks and porches.
Retaining walls that hold back more than a set height, or support a load, need a permit (see retaining wall permits by state).
Permit exemptions, such as small sheds, fences under a set height, patios and low decks, are listed in the code’s permit section and often changed by states and towns.

Builder’s note: Pennsylvania runs the Uniform Construction Code, which adopted the 2021 IRC with state changes on January 1, 2026. One we work with all the time: Pennsylvania still allows stair risers up to 8 1/4 in. with a 9 in. minimum tread, where the model IRC says 7 3/4 in. and 10 in. Small state amendments like that are why the edition alone doesn’t tell the whole story.

Find your state:Jumps to your state’s full entry, with the official sources.

Residential building codes in all 50 states

State	Residential code	How it applies	In effect since
Alabama	2015 IRC	Statewide for some areas only	October 1, 2016
Alaska	Local codes	Local adoption (no statewide residential code)	—
Arizona	Local codes	Local adoption (no statewide residential code)	—
Arkansas	2021 IRC	Statewide minimum, local amendments allowed	January 1, 2023
California	2024 IRC	Statewide minimum, local amendments allowed	January 1, 2026
Colorado	Local codes	Local adoption (no statewide residential code)	—
Connecticut	2021 IRC	Statewide, mandatory everywhere	October 1, 2022
Delaware	Local codes	Local adoption (no statewide residential code)	—
District of Columbia	2015 IRC	Statewide, mandatory everywhere	May 29, 2020
Florida	2021 IRC	Statewide, mandatory everywhere	December 31, 2023
Georgia	2024 IRC	Statewide, mandatory everywhere	—
Hawaii	2018 IRC	Statewide, applies only where locally enforced	—
Idaho	2018 IRC	Statewide, applies only where locally enforced	January 1, 2021
Illinois	Local codes	Local adoption (no statewide residential code)	—
Indiana	2018 IRC	Statewide, mandatory everywhere	December 26, 2019
Iowa	2024 IRC	Statewide for some areas only	September 10, 2025
Kansas	Local codes	Local adoption (no statewide residential code)	—
Kentucky	2015 IRC	Statewide, mandatory everywhere	December 3, 2024
Louisiana	2021 IRC	Statewide, mandatory everywhere	January 1, 2023
Maine	2021 IRC	Statewide for some areas only	April 7, 2025
Maryland	2021 IRC	Statewide minimum, local amendments allowed	May 29, 2023
Massachusetts	2021 IRC	Statewide, mandatory everywhere	October 11, 2024
Michigan	2021 IRC	Statewide, mandatory everywhere	August 29, 2025
Minnesota	2018 IRC	Statewide, mandatory everywhere	March 31, 2020
Mississippi	Local codes	Statewide, but municipalities can opt out	—
Missouri	Local codes	Local adoption (no statewide residential code)	—
Montana	2024 IRC	Statewide, applies only where locally enforced	September 26, 2026
Nebraska	2018 IRC	Statewide minimum, local amendments allowed	—
Nevada	Local codes	Local adoption (no statewide residential code)	—
New Hampshire	2024 IRC	Statewide, mandatory everywhere	July 1, 2026
New Jersey	2024 IRC	Statewide, mandatory everywhere	August 17, 2026
New Mexico	2021 IRC	Statewide, mandatory everywhere	July 14, 2023
New York	2024 IRC	Statewide, mandatory everywhere	December 31, 2025
North Carolina	2015 IRC	Statewide, mandatory everywhere	January 1, 2019
North Dakota	2024 IRC	Statewide, applies only where locally enforced	January 1, 2026
Ohio	2018 IRC	Statewide, mandatory everywhere	July 1, 2019
Oklahoma	2024 IRC	Statewide minimum, local amendments allowed	September 14, 2026
Oregon	2024 IRC	Statewide, mandatory everywhere	October 1, 2026
Pennsylvania	2021 IRC	Statewide, but municipalities can opt out	January 1, 2026
Rhode Island	2021 IRC	Statewide, mandatory everywhere	December 1, 2025
South Carolina	2021 IRC	Statewide, mandatory everywhere	January 1, 2023
South Dakota	Local codes	Local adoption (no statewide residential code)	—
Tennessee	2018 IRC	Statewide, but municipalities can opt out	July 16, 2020
Texas	2012 IRC	Statewide for some areas only	January 1, 2022
Utah	2021 IRC	Statewide, mandatory everywhere	July 1, 2023
Vermont	Local codes	Local adoption (no statewide residential code)	—
Virginia	2021 IRC	Statewide, mandatory everywhere	January 18, 2024
Washington	2021 IRC	Statewide minimum, local amendments allowed	March 15, 2024
West Virginia	2018 IRC	Statewide, applies only where locally enforced	August 1, 2022
Wisconsin	Local codes	Statewide, mandatory everywhere	—
Wyoming	Local codes	Local adoption (no statewide residential code)	—

One- and two-family dwellings. State amendments, the agency, upcoming editions and the adopting rule for each state are below.

State-by-state details

AlabamaOfficial source

Residential code: 2015 International Residential Code with Alabama amendments (Alabama Residential Building Code)
How it applies: Statewide for some areas only
In effect since: October 1, 2016
Code agency: Alabama Energy and Residential Codes Board (Alabama Department of Economic and Community Affairs, ADECA)
Who enforces it: Applies to jurisdictions that had no residential code before March 2010; jurisdictions that already had a residential code may keep enforcing it. Permits and inspections are handled by local building departments.
Adopted by: Ala. Admin. Code r. 305-2-4-.09 (Act 2010-185)
Good to know: Alabama's state residential code is still based on the 2015 IRC, and cities that had their own code before 2010 may use a different edition. Check with your city or county building department before you build.

Sources: adeca.alabama.gov · admincode.legislature.state.al.us · fema.gov

AlaskaSecondary source

Residential code: No statewide residential code; cities and boroughs adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for one- and two-family homes (Alaska Department of Public Safety, Division of Fire and Life Safety, reviews larger buildings)
Who enforces it: State fire and life safety plan review exempts residential buildings of three units or fewer. Cities such as Anchorage, Fairbanks and Juneau enforce their own codes; many areas have no residential permits or inspections.
Good to know: Alaska has no statewide building code for houses, and state plan review skips homes with three or fewer units. Some cities and boroughs adopt their own codes, so check with your local government before you build.

Sources: dps.alaska.gov · adn.com

ArizonaSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None (no state agency sets a code for one- and two-family homes)
Who enforces it: Counties may adopt building codes for zoned unincorporated areas and may exempt areas zoned rural or unclassified, so some rural areas have no residential code.
Adopted by: A.R.S. § 11-861 (county adoption of building codes, optional)
Good to know: Arizona has no statewide house code. Your city or county sets the code, and counties may exempt rural-zoned areas from their building code.

Sources: azleg.gov · law.justia.com · fema.gov

ArkansasOfficial source

Residential code: 2021 International Residential Code as amended by the State Fire Marshal (Arkansas Fire Prevention Code, Volume III)
How it applies: Statewide minimum, local amendments allowed
In effect since: January 1, 2023
Code agency: Arkansas State Fire Marshal's Office (Arkansas Department of Public Safety)
Who enforces it: Cities and counties may only adopt and enforce the Arkansas Fire Prevention Code but may add stricter rules. Inspection depends on whether a local building department exists.
Adopted by: 015.01.22 Ark. Code R. § 005 (2021 Arkansas Fire Prevention Code)
Good to know: Arkansas uses the 2021 IRC statewide as part of its Fire Prevention Code. Whether a building inspector checks your project depends on your city or county.

Sources: dps.arkansas.gov · law.cornell.edu

CaliforniaOfficial source

Residential code: 2025 California Residential Code (California Code of Regulations Title 24, Part 2.5), based on the 2024 International Residential Code
How it applies: Statewide minimum, local amendments allowed
In effect since: January 1, 2026
Code agency: California Building Standards Commission (with the Department of Housing and Community Development for residential provisions)
Who enforces it: Cities and counties enforce the code and may adopt stricter local amendments.
Adopted by: California Code of Regulations, Title 24, Part 2.5 (California Residential Code)
Good to know: California's residential code is rewritten every three years and the current 2025 edition is based on the 2024 IRC. Many cities add their own stricter rules, so check with your local building department.

Sources: dgs.ca.gov · dgs.ca.gov

ColoradoOfficial source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for private homes (the Office of the State Architect sets codes for state-agency buildings)
Who enforces it: Cities and counties adopt and enforce their own codes; areas that have not adopted a code may have no building permits or inspections.
Good to know: Colorado has no statewide house code. Your city or county decides which code applies, so the edition can differ from one side of a county line to the other.

Sources: osa.colorado.gov · mitek-us.com

ConnecticutOfficial source

Residential code: 2021 International Residential Code with Connecticut amendments (2022 Connecticut State Building Code)
How it applies: Statewide, mandatory everywhere
In effect since: October 1, 2022
Code agency: Department of Administrative Services, Office of the State Building Inspector
Who enforces it: Enforced by each town's building official.
Adopted by: Conn. Gen. Stat. § 29-252 (2022 Connecticut State Building Code)
Good to know: Connecticut's 2026 State Building Code, expected to use the 2024 IRC, has been delayed. Until it is approved, the 2022 code (2021 IRC) applies.

Sources: portal.ct.gov · prdext3.cga.ct.gov · brookfieldct.gov · portal.ct.gov

DelawareSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for the residential building code (counties and municipalities adopt)
Who enforces it: Counties and municipalities adopt and enforce their own codes.
Good to know: Delaware has no statewide house code. Your county or town sets the code and issues permits.

Sources: fema.gov · mitek-us.com

District of ColumbiaOfficial source

Residential code: 2015 International Residential Code with DC amendments (2017 DC Construction Codes, 12-B DCMR DC Residential Code)
How it applies: Statewide, mandatory everywhere
In effect since: May 29, 2020
Code agency: DC Department of Buildings (DOB)
Who enforces it: DC is a single jurisdiction; DOB issues permits and inspects.
Adopted by: DC Municipal Regulations Title 12, Subtitle B (DC Residential Code Amendments)
Good to know: DC still uses a residential code based on the 2015 IRC. DOB's schedule shows a new code edition being finalized in late 2027, so ask DOB which edition applies when you file for a permit.

Sources: dob.dc.gov · dob.dc.gov · awc.org · fema.gov · dob.dc.gov

FloridaOfficial source

Residential code: Florida Building Code, Residential, 8th Edition (2023), based on the 2021 International Residential Code
How it applies: Statewide, mandatory everywhere
In effect since: December 31, 2023
Coming next: Florida Building Code, Residential, 9th Edition (2026), based on the 2024 IRC, scheduled to take effect December 31, 2026 (final rule adoption was still pending in the Commission's October 2026 workplan)
Code agency: Florida Building Commission (Department of Business and Professional Regulation)
Who enforces it: Enforced by county and city building departments. Local governments may adopt stricter technical amendments only after a hearing showing local need.
Adopted by: Fla. Stat. § 553.73 (Florida Building Code); Fla. Admin. Code r. 61G20-1.001
Good to know: Florida has one statewide building code with its own residential volume, currently based on the 2021 IRC. A new 9th Edition based on the 2024 IRC is scheduled to take effect December 31, 2026, so ask your building department which edition applies to your permit.

Sources: floridabuilding.org · leg.state.fl.us · floridabuilding.org · floridabuilding.org · icc-nta.org · fema.gov

GeorgiaSecondary source

Residential code: 2024 International Residential Code with Georgia amendments (Georgia State Minimum Standard Codes)
How it applies: Statewide, mandatory everywhere
Coming next: Georgia's current-codes page already lists the 2024 IRC, but a December 9, 2025 state notice gives January 1, 2027 as its effective date
Code agency: Georgia Department of Community Affairs (DCA), Construction Codes Program
Who enforces it: The IRC is a mandatory state code: homes must comply whether or not the city or county enforces it. Local governments choose whether to run permits and inspections. Georgia uses the IPC, NEC and 2015 IECC instead of the IRC's plumbing, electrical and energy chapters.
Adopted by: O.C.G.A. § 8-2-20(9)(B) (Uniform Codes Act, mandatory codes)
Good to know: Georgia has adopted the 2024 IRC with Georgia amendments, and it applies statewide even where a county doesn't inspect. The state's own pages give different start dates (January 2026 and January 2027), so ask your local building department which edition it's enforcing on your permit. Georgia uses separate state codes for plumbing, electrical and energy.

Sources: dca.georgia.gov · dca.georgia.gov · dca.georgia.gov · dca.georgia.gov · dca.georgia.gov · dca.georgia.gov

HawaiiSecondary source

Residential code: Hawaii State Building Code residential code (2018 IRC adopted by the State Building Code Council; the 2021 IRC was adopted by default without state amendments); each county enforces its own amended code, currently based on the 2018 I-Codes
How it applies: Statewide, applies only where locally enforced
Code agency: Hawaii State Building Code Council (Department of Accounting and General Services)
Who enforces it: Honolulu, Maui, Hawaii and Kauai counties adopt and enforce their own versions. Under the Governor's affordable-housing emergency proclamations, the two-year deadline for counties to adopt state codes and the Council's code updates are suspended.
Adopted by: Hawaii Revised Statutes Chapter 107, Part II (State Building Code; §§ 107-24, 107-28)
Good to know: Each Hawaii county adopts and enforces its own building code, currently based on the 2018 IRC with county amendments. State code updates are suspended under the Governor's affordable-housing emergency proclamation, so check with your county building department.

Sources: ags.hawaii.gov · ags.hawaii.gov · fema.gov

IdahoSecondary source

Residential code: 2018 International Residential Code (Parts I-III and IX) with Idaho amendments (Idaho Residential Code, 2020 Edition)
How it applies: Statewide, applies only where locally enforced
In effect since: January 1, 2021
Code agency: Idaho Division of Occupational and Professional Licenses (Idaho Building Code Board)
Who enforces it: Cities and counties that issue building permits must adopt the Idaho Residential Code and cannot make it stricter; local building programs are optional, so some rural areas have no residential permits. Sprinklers cannot be required in one- and two-family homes.
Adopted by: Idaho Code §§ 39-4109 and 39-4116
Good to know: Idaho uses the 2018 IRC with state amendments, and local codes can't be stricter. Some rural counties don't issue residential building permits, so check with your county.

Sources: dopl.idaho.gov · legislature.idaho.gov · legislature.idaho.gov · cityofwilder.org · awc.org · legislature.idaho.gov

IllinoisSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for residential construction
Who enforces it: In areas with no building code, a new-home contract must name the IRC or a local code within 100 miles; if it names none, the current IRC applies by law.
Adopted by: Residential Building Code Act, 815 ILCS 670
Good to know: Illinois has no statewide house code. Where your town or county has no code, Illinois law makes the current IRC the default standard in a new-home contract.

Sources: ilga.gov · fema.gov · mitek-us.com

IndianaOfficial source

Residential code: 2018 International Residential Code with Indiana amendments (2020 Indiana Residential Code, 675 IAC 14-4.4)
How it applies: Statewide, mandatory everywhere
In effect since: December 26, 2019
Code agency: Indiana Fire Prevention and Building Safety Commission (Indiana Department of Homeland Security)
Who enforces it: Enforced by county and city building departments.
Adopted by: 675 IAC 14-4.4 (2020 Indiana Residential Code)
Good to know: Indiana's residential code is based on the 2018 IRC. Your county or city building department issues permits and inspects.

Sources: in.gov · fema.gov · mitek-us.com

IowaOfficial source

Residential code: 2024 International Residential Code with Iowa amendments (Iowa State Building Code, 481 IAC 301.8), for buildings covered by the state code; other cities and counties adopt their own codes
How it applies: Statewide for some areas only
In effect since: September 10, 2025
Code agency: Iowa Department of Inspections, Appeals, and Licensing, Building Code Bureau
Who enforces it: The state code applies to state-owned and state-funded buildings, local governments that adopt it by ordinance, and cities over 15,000 without an equivalent local code. Other cities and counties set their own code; areas with no local code may have no permits. State energy standards apply to nearly all new construction.
Adopted by: Iowa Code § 103A.10; Iowa Admin. Code r. 481-301.8
Good to know: Iowa's state building code uses the 2024 IRC, but for most homes it applies only where the city or county has adopted it. Many Iowa cities and counties enforce their own adopted code, so check locally.

Sources: legis.iowa.gov · legis.iowa.gov · dial.iowa.gov · fema.gov

KansasSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for residential construction
Who enforces it: Cities and counties adopt and enforce their own codes; areas that have not adopted a code may have no building permits or inspections.
Good to know: Kansas has no statewide house code. Your city or county decides what applies, and places that haven't adopted a code may not require building permits.

Sources: fema.gov · mitek-us.com

KentuckyOfficial source

Residential code: 2018 Kentucky Residential Code (3rd edition, August 2024), based on the 2015 International Residential Code
How it applies: Statewide, mandatory everywhere
In effect since: December 3, 2024
Code agency: Kentucky Department of Housing, Buildings and Construction
Who enforces it: The code applies to all new homes, but permits, inspections and certificates of occupancy for single-family homes are required only where a local ordinance requires them.
Adopted by: 815 KAR 7:125 (Kentucky Residential Code)
Good to know: Kentucky's statewide residential code is still based on the 2015 IRC. Inspections for single-family homes happen only where your city or county requires them.

Sources: apps.legislature.ky.gov · fema.gov · mitek-us.com

LouisianaOfficial source

Residential code: 2021 International Residential Code with Louisiana amendments (Louisiana State Uniform Construction Code)
How it applies: Statewide, mandatory everywhere
In effect since: January 1, 2023
Code agency: Louisiana Uniform Construction Code Commission (LUCCC)
Who enforces it: Parishes and municipalities must enforce the code for new homes, additions to homes built under the IRC, and major alterations.
Adopted by: La. R.S. 40:1730.28; La. Admin. Code tit. 17, pt. I, § 107
Good to know: Louisiana enforces the 2021 IRC statewide. The state has proposed moving to the 2024 codes (notice published August 2026), so check the effective date before a 2027 project.

Sources: doa.louisiana.gov · dotd.la.gov · icc-nta.org · luccc.louisiana.gov

MaineOfficial source

Residential code: 2021 International Residential Code with Maine amendments (Maine Uniform Building and Energy Code, MUBEC)
How it applies: Statewide for some areas only
In effect since: April 7, 2025
Code agency: Maine Office of Community Affairs, Division of Building Codes and Standards
Who enforces it: Must be enforced in towns with more than 4,000 residents. Smaller towns may choose to enforce it but cannot adopt any other building code.
Adopted by: 10 M.R.S. § 9724 (Maine Uniform Building and Energy Code)
Good to know: Maine's code is required in towns of more than 4,000 people. In smaller towns, ask the town office whether it enforces the code.

Sources: maine.gov · legislature.maine.gov

MarylandOfficial source

Residential code: 2021 International Residential Code (Maryland Building Performance Standards, COMAR 09.12.51)
How it applies: Statewide minimum, local amendments allowed
In effect since: May 29, 2023
Code agency: Maryland Department of Labor, Building Codes Administration
Who enforces it: Counties and municipalities must implement and enforce the Standards within 12 months of each state update (May 29, 2024 for the 2021 codes) and may amend them for local conditions, with limits on energy, sprinkler and wind provisions.
Adopted by: COMAR 09.12.51.04-.06 (Maryland Building Performance Standards)
Good to know: Maryland uses the 2021 IRC, but each county can amend it, so rules in Montgomery County may differ from those in Frederick or Baltimore County.

Sources: labor.md.gov · regs.maryland.gov · law.cornell.edu · icc-nta.org · labor.maryland.gov · fema.gov

MassachusettsOfficial source

Residential code: 2021 International Residential Code with Massachusetts amendments (780 CMR, 10th Edition, Chapter 51 Massachusetts Residential Code)
How it applies: Statewide, mandatory everywhere
In effect since: October 11, 2024
Code agency: Board of Building Regulations and Standards (BBRS)
Who enforces it: Enforced by each city or town building commissioner or inspector.
Adopted by: 780 CMR, Tenth Edition, Chapter 51
Good to know: Massachusetts' residential code is based on the 2021 IRC with state amendments, and it applies in every city and town.

Sources: mass.gov · mass.gov · fema.gov

MichiganOfficial source

Residential code: 2021 Michigan Residential Code (2021 International Residential Code with Michigan amendments)
How it applies: Statewide, mandatory everywhere
In effect since: August 29, 2025
Code agency: Michigan Department of Licensing and Regulatory Affairs (LARA), Bureau of Construction Codes
Who enforces it: Enforced by local, county or state building officials depending on the community; LARA's Bureau of Construction Codes keeps a statewide jurisdiction list.
Adopted by: Mich. Admin. Code R 408.30500 (Part 5, Residential Code)
Good to know: Michigan moved to a residential code based on the 2021 IRC on August 29, 2025. Older guides and some web pages still cite the 2015 code.

Sources: law.cornell.edu · icc-nta.org · house.mi.gov · michigan.gov · fema.gov

MinnesotaOfficial source

Residential code: 2020 Minnesota Residential Code (2018 International Residential Code with Minnesota amendments, Minn. R. ch. 1309), part of the Minnesota State Building Code
How it applies: Statewide, mandatory everywhere
In effect since: March 31, 2020
Code agency: Minnesota Department of Labor and Industry, Construction Codes and Licensing Division
Who enforces it: The State Building Code is the legal minimum everywhere in Minnesota, but cities and counties can only enforce it after adopting it by ordinance, so areas that haven't adopted it may have no permits or inspections.
Adopted by: Minn. R. 1309.0010
Good to know: Minnesota's code is the legal minimum everywhere, but it's only inspected where a city or county has adopted it. The state has started work on moving to the 2024 IRC.

Sources: dli.mn.gov · revisor.mn.gov · dli.mn.gov · dli.mn.gov · fema.gov

MississippiSecondary source

Residential code: Codes adopted by the Mississippi Building Codes Council; cities and counties that did not opt out in 2014 must use one of the three most recent IRC editions, and coastal counties must enforce the state code
How it applies: Statewide, but municipalities can opt out
Code agency: Mississippi Building Codes Council
Who enforces it: Local governments could opt out of the 2014 statewide code. Coastal counties are required to adopt and enforce it. Elsewhere, whether codes are enforced depends on the city or county.
Adopted by: Mississippi Building Codes Act of 2014 (Miss. Code Ann. Title 41, Chapter 26)
Good to know: Mississippi's coastal counties must adopt and enforce the state building code. Elsewhere, cities and counties could opt out in 2014, and those that enforce a code use one of the IRC editions the state allows, so check with your local building office.

Sources: iccsafe.org · iccsafe.org · awc.org · usglassmag.com · icc-nta.org · fema.gov

MissouriSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for private homes
Who enforces it: Cities and counties adopt and enforce their own codes; areas that have not adopted a code may have no building permits or inspections.
Good to know: Missouri has no statewide house code. Your city or county decides what applies, and places that haven't adopted a code may not require building permits.

Sources: fema.gov · mitek-us.com

MontanaOfficial source

Residential code: 2024 International Residential Code with Montana amendments (ARM Title 24, Chapter 301)
How it applies: Statewide, applies only where locally enforced
In effect since: September 26, 2026
Code agency: Montana Department of Labor & Industry, Building Codes Program
Who enforces it: The state building code does not apply to residential buildings with fewer than five units (or to farm and ranch buildings) unless the city or county has adopted it by ordinance. Cities and counties with certified programs enforce it.
Adopted by: Mont. Code Ann. § 50-60-102; ARM 24.301.154
Good to know: Montana's code moved to the 2024 IRC on September 26, 2026, but the state code only covers houses where your city or county has adopted it. Outside those areas, houses aren't inspected for the building code.

Sources: bsd.dli.mt.gov · bsd.dli.mt.gov · mca.legmt.gov · law.cornell.edu · fema.gov

NebraskaOfficial source

Residential code: 2018 International Residential Code, excluding section R313 and chapters 25-33 (Nebraska state building code, Neb. Rev. Stat. § 71-6403)
How it applies: Statewide minimum, local amendments allowed
Code agency: None; set by statute (Nebraska Building Construction Act)
Who enforces it: Counties, cities and villages that adopt a code must use the state code or one that conforms generally with it; if they fail to adopt one within two years of a state update, the state code applies there by default (except farm construction). Enforcement is local.
Adopted by: Neb. Rev. Stat. §§ 71-6403 and 71-6406
Good to know: Nebraska's state code is the 2018 IRC without its sprinkler requirement. Local codes must generally match it, but permits and inspections depend on your city or county.

Sources: nebraskalegislature.gov · nebraskalegislature.gov · fema.gov · mitek-us.com

NevadaSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for private homes (the State Public Works Division adopts codes for state projects)
Who enforces it: Counties and cities adopt and enforce their own codes. The state's 2024 IRC adoption (NAC 341.045) is for state Public Works projects.
Good to know: Nevada has no statewide house code. Your county or city adopts and enforces the code that applies to your home.

Sources: fema.gov · publicworks.nv.gov · mitek-us.com

New HampshireOfficial source

Residential code: 2024 International Residential Code with New Hampshire amendments (New Hampshire State Building Code, RSA 155-A)
How it applies: Statewide, mandatory everywhere
In effect since: July 1, 2026
Code agency: New Hampshire State Building Code Review Board (State Fire Marshal's Office, Department of Safety)
Who enforces it: The State Building Code applies in every municipality. Towns that choose to enforce it adopt an ordinance confirmed by the Building Code Review Board; since July 1, 2026, local amendments are limited to administrative matters. Permit applications could use either the 2021 or 2024 code from July 1 to December 31, 2026; from January 1, 2027, the 2024 code applies.
Adopted by: RSA 155-A (New Hampshire Building Code)
Good to know: New Hampshire's state building code moved to the 2024 IRC on July 1, 2026, and it applies in every town. Permit applications filed through December 31, 2026 may still use the 2021 code; from January 1, 2027, the 2024 code applies.

Sources: fema.gov · mitek-us.com · firemarshal.dos.nh.gov

New JerseyOfficial source

Residential code: 2024 International Residential Code, New Jersey edition (Uniform Construction Code, N.J.A.C. 5:23-3.21)
How it applies: Statewide, mandatory everywhere
In effect since: August 17, 2026
Code agency: New Jersey Department of Community Affairs, Division of Codes and Standards
Who enforces it: Enforced by municipal construction offices. Permit applications may use the previous (2021-based) codes through February 17, 2027.
Adopted by: N.J.A.C. 5:23-3.21 (Uniform Construction Code)
Good to know: New Jersey switched to the 2024 IRC on August 17, 2026, but permit applications can still use the older code through February 17, 2027. New Jersey did not adopt the IRC's sprinkler requirement for one- and two-family homes.

Sources: nj.gov · nj.gov · nj.gov · fema.gov

New MexicoOfficial source

Residential code: 2021 New Mexico Residential Building Code (2021 International Residential Code as amended, 14.7.3 NMAC)
How it applies: Statewide, mandatory everywhere
In effect since: July 14, 2023
Code agency: New Mexico Regulation and Licensing Department, Construction Industries Division (CID)
Who enforces it: Required for all work on or after December 14, 2023. Permits are issued by CID or by cities and counties that run their own building departments.
Adopted by: 14.7.3 NMAC (2021 New Mexico Residential Building Code)
Good to know: New Mexico uses the 2021 IRC statewide. Depending on where you live, permits come from the state Construction Industries Division or your city or county.

Sources: srca.nm.gov · rld.nm.gov · fema.gov

New YorkOfficial source

Residential code: 2025 Residential Code of New York State (2025 Uniform Code, based on the 2024 ICC codes)
How it applies: Statewide, mandatory everywhere
In effect since: December 31, 2025
Code agency: New York Department of State, Division of Building Standards and Codes
Who enforces it: Cities, towns, villages and counties enforce the Uniform Code. New York City has its own construction codes.
Adopted by: 19 NYCRR Part 1220 (2025 Residential Code of New York State)
Good to know: New York's 2025 residential code, based on the 2024 IRC, took effect December 31, 2025. New York City has its own construction codes.

Sources: dos.ny.gov · dos.ny.gov · dos.ny.gov · fema.gov · nyc.gov

North CarolinaOfficial source

Residential code: 2018 North Carolina Residential Code (based on the 2015 International Residential Code)
How it applies: Statewide, mandatory everywhere
In effect since: January 1, 2019
Code agency: North Carolina Building Code Council and Residential Code Council (staffed by the Office of State Fire Marshal)
Who enforces it: Enforced by county and city inspection departments. The adopted 2024 code (2021 IRC basis) is on hold until 12 months after the State Fire Marshal certifies that it is published and the Residential Code Council is fully appointed.
Adopted by: N.C. Gen. Stat. § 143-138 (North Carolina State Building Code); S.L. 2025-2 (delay of 2024 code)
Good to know: North Carolina still uses its 2018 residential code, based on the 2015 IRC. A newer 2024 code has been adopted but is on hold, and it will take effect 12 months after the state announces it is ready.

Sources: ncosfm.gov · ncosfm.gov · ncosfm.gov · fema.gov

North DakotaOfficial source

Residential code: 2024 International Residential Code with North Dakota amendments (North Dakota State Building Code)
How it applies: Statewide, applies only where locally enforced
In effect since: January 1, 2026
Code agency: North Dakota Department of Commerce, Division of Community Services (Building Codes)
Who enforces it: Cities, counties and townships are not required to enforce a building code; those that do must adopt the State Building Code and may amend it for local needs.
Adopted by: N.D. Cent. Code ch. 54-21.3 (State Building Code)
Good to know: North Dakota's state code moved to the 2024 IRC on January 1, 2026, but only places that choose to enforce a building code use it. In rural areas, ask your county or township whether permits are required.

Sources: commerce.nd.gov · ndlegis.gov · fema.gov

OhioOfficial source

Residential code: Residential Code of Ohio (2018 International Residential Code, first printing, with Ohio amendments; Ohio Adm. Code 4101:8)
How it applies: Statewide, mandatory everywhere
In effect since: July 1, 2019
Code agency: Ohio Board of Building Standards (Department of Commerce)
Who enforces it: Enforced by certified municipal, township or county residential building departments. Where none is certified, owners are not required to submit plans or get inspections, though the code still applies.
Adopted by: Ohio Adm. Code 4101:8-1-01 (Residential Code of Ohio)
Good to know: Ohio's residential code is based on the 2018 IRC and covers one-, two- and three-family homes. In areas without a certified residential building department, no permit or inspection is required, but the work should still meet the code.

Sources: codes.ohio.gov · law.cornell.edu · com.ohio.gov · icc-nta.org · fema.gov

OklahomaOfficial source

Residential code: 2024 International Residential Code with Oklahoma amendments (OAC 748:20-6)
How it applies: Statewide minimum, local amendments allowed
In effect since: September 14, 2026
Code agency: Oklahoma Uniform Building Code Commission (OUBCC)
Who enforces it: Cities and counties enforce the code and may amend it only as Oklahoma law allows.
Adopted by: OAC 748:20-6 (59 O.S. § 1000.23)
Good to know: Oklahoma's statewide minimum residential code moved to the 2024 IRC on September 14, 2026. Permits and inspections are handled by your city or county, so check locally before you build.

Sources: oklahoma.gov · oklahoma.gov · fema.gov · mitek-us.com

OregonOfficial source

Residential code: 2026 Oregon Residential Specialty Code (based on the 2024 International Residential Code)
How it applies: Statewide, mandatory everywhere
In effect since: October 1, 2026
Code agency: Oregon Department of Consumer and Business Services, Building Codes Division
Who enforces it: Chapter 1 is mandatory from October 1, 2026; for Chapters 2-44 the 2023 code may still be used until the 2026 code becomes mandatory April 1, 2027. Local governments cannot add building requirements beyond the state code, except for a few items such as some fences and retaining walls.
Adopted by: OAR 918-480-0005 (Oregon Residential Specialty Code)
Good to know: Oregon's 2026 residential code, based on the 2024 IRC, took effect October 1, 2026. Until April 1, 2027, builders may still design to the 2023 code for most chapters.

Sources: oregon.gov · oregon.gov · law.cornell.edu

PennsylvaniaOfficial source

Residential code: 2021 International Residential Code with Pennsylvania modifications (Uniform Construction Code, 34 Pa. Code Chapter 403)
How it applies: Statewide, but municipalities can opt out
In effect since: January 1, 2026
Code agency: Pennsylvania Department of Labor & Industry (Uniform Construction Code)
Who enforces it: Enforced by municipalities or their third-party agencies. In municipalities that opted out, the owner or contractor hires a certified third-party agency for residential inspections, and L&I handles commercial work.
Adopted by: Pennsylvania Construction Code Act (35 P.S. § 7210.101 et seq.); 34 Pa. Code § 403.21 (amended Nov. 7, 2025, effective Jan. 1, 2026, 55 Pa.B. 7701)
Good to know: Pennsylvania moved to the 2021 IRC on January 1, 2026. Pennsylvania's version still allows stair risers up to 8 1/4 in. with treads at least 9 in. deep in homes, instead of the IRC's 7 3/4 in. riser and 10 in. tread.

Sources: pa.gov · irrc.state.pa.us · irrc.state.pa.us · law.cornell.edu · manheimtownship.org · legis.state.pa.us

Rhode IslandOfficial source

Residential code: 2021 International Residential Code with Rhode Island amendments (RISBC-2, Rhode Island State One and Two Family Dwelling Code)
How it applies: Statewide, mandatory everywhere
In effect since: December 1, 2025
Code agency: Rhode Island Building Code Commission (State Building Office)
Who enforces it: Enforced by each city or town building official.
Adopted by: 510-RICR-00-00-2 (R.I. Gen. Laws §§ 23-27.3-100.1.5 and 23-27.3-109.1)
Good to know: Rhode Island's residential code moved to the 2021 IRC on December 1, 2025. Your city or town building official issues permits and inspects.

Sources: rules.sos.ri.gov · northkingstownri.gov · ribcc.ri.gov · fema.gov

South CarolinaOfficial source

Residential code: 2021 International Residential Code with South Carolina modifications (2021 South Carolina Building Codes)
How it applies: Statewide, mandatory everywhere
In effect since: January 1, 2023
Coming next: 2024 South Carolina Building Codes, including the 2024 IRC, take effect January 1, 2027
Code agency: South Carolina Building Codes Council (Department of Labor, Licensing and Regulation)
Who enforces it: Every municipality and county must enforce the mandatory codes. Some local modifications approved by the Council can be adopted by local ordinance.
Adopted by: S.C. Code Ann. § 6-9-50 (mandatory building codes)
Good to know: South Carolina uses the 2021 IRC statewide, and every county and city must enforce it. The 2024 IRC takes effect January 1, 2027, so projects permitted after that date follow the newer code.

Sources: llr.sc.gov · llr.sc.gov · llr.sc.gov · llr.sc.gov · fema.gov

South DakotaOfficial source

Residential code: No statewide residential code; cities and towns that adopt one must use the 2024 IRC (SDCL 11-10-12)
How it applies: Local adoption (no statewide residential code)
Code agency: None for residential construction
Who enforces it: No statewide residential code. Under SDCL 11-10-12 (amended 2026), a city or town that adopts a residential code does so by adopting the 2024 IRC; it may amend the code but may not require sprinklers or impose requirements stricter than the 2024 IRC. Areas without a local code may have no building permits.
Adopted by: SDCL 11-10-12 (municipal adoption of the International Residential Code)
Good to know: South Dakota has no statewide house code. Cities and towns that adopt a residential code must use the 2024 IRC (they can amend it but can't make it stricter), and places without a code may not require building permits.

Sources: fema.gov · awc.org · mitek-us.com · sdlegislature.gov · sdlegislature.gov

TennesseeOfficial source

Residential code: 2018 International Residential Code with Tennessee amendments (adopted by the State Fire Marshal, Rule 0780-02-23-.02)
How it applies: Statewide, but municipalities can opt out
In effect since: July 16, 2020
Code agency: Tennessee State Fire Marshal's Office, Codes Enforcement (Department of Commerce & Insurance)
Who enforces it: Cities and counties that enforce their own residential code are exempt, and local governments may opt out of state residential enforcement. Elsewhere, permits come through state-authorized permit agents. Sprinklers are not required in homes.
Adopted by: Tenn. Comp. R. & Regs. 0780-02-23-.02 and -.05
Good to know: Tennessee's state residential code is based on the 2018 IRC. Many cities and counties enforce their own code instead, so check who issues permits where you live.

Sources: tn.gov · tn.gov · regulations.justia.com · regulations.justia.com · fema.gov

TexasOfficial source

Residential code: 2012 International Residential Code (as it existed May 1, 2012) as the municipal residential building code; cities may adopt later editions and local amendments
How it applies: Statewide for some areas only
In effect since: January 1, 2022
Code agency: None (set by statute; no state residential code agency)
Who enforces it: Applies inside city limits, where cities may adopt newer IRC editions and amend the code. County authority over home construction outside city limits is separate and much more limited.
Adopted by: Tex. Local Gov't Code § 214.212
Good to know: Texas sets the 2012 IRC as the baseline only inside city limits, and cities may adopt newer editions. Outside city limits, ask your county what rules apply.

Sources: texas.public.law · capitol.texas.gov · fema.gov · mitek-us.com · statutes.capitol.texas.gov

UtahOfficial source

Residential code: 2021 International Residential Code with Utah amendments (State Construction Code, Utah Code Title 15A)
How it applies: Statewide, mandatory everywhere
In effect since: July 1, 2023
Code agency: Utah Uniform Building Code Commission and Division of Professional Licensing (Department of Commerce)
Who enforces it: Enforced by cities and counties. Amendments are made by the Legislature. HB 65 (2026) moved most other codes to 2024 editions but kept the 2021 IRC.
Adopted by: Utah Code §§ 15A-2-103 and 15A-3-202 (as amended by HB 65, 2026)
Good to know: Utah kept the 2021 IRC for houses in 2026 even as it moved other codes to the 2024 editions. Utah adds its own amendments, including rules for accessory dwelling units.

Sources: le.utah.gov · le.utah.gov · iccsafe.org · fema.gov

VermontSecondary source

Residential code: No statewide building code for owner-occupied single-family homes; the state Residential Building Energy Standards (30 V.S.A. § 51) still apply to new homes
How it applies: Local adoption (no statewide residential code)
Code agency: None for owner-occupied homes (the Division of Fire Safety regulates public buildings, which include rental housing)
Who enforces it: Owner-occupied single-family homes are not 'public buildings' under state law, so the state fire and building safety code does not cover them; homes that are rented are treated as public buildings. The Residential Building Energy Standards apply to all new homes and to additions, alterations and repairs of residential buildings.
Adopted by: 20 V.S.A. § 2730 (definition of public building)
Good to know: Vermont has no statewide building code for owner-occupied single-family homes, but the state's Residential Building Energy Standards apply to all new homes and additions. If you rent the home out, it is treated as a public building and state fire and building safety rules apply.

Sources: legislature.vermont.gov · firesafety.vermont.gov · fema.gov · mitek-us.com · publicservice.vermont.gov

VirginiaOfficial source

Residential code: 2021 Virginia Residential Code (2021 International Residential Code with Virginia amendments, part of the 2021 Uniform Statewide Building Code)
How it applies: Statewide, mandatory everywhere
In effect since: January 18, 2024
Code agency: Virginia Department of Housing and Community Development (Board of Housing and Community Development)
Who enforces it: Enforced by county and city building departments. The USBC supersedes local building codes, so localities cannot adopt their own.
Adopted by: 13VAC5-63 (Virginia Uniform Statewide Building Code); Code of Virginia § 36-98
Good to know: Virginia uses one statewide code, based on the 2021 IRC, and localities can't adopt their own. A 2024-based update is in development, so ask your building department which edition applies.

Sources: dhcd.virginia.gov · dhcd.virginia.gov · register.dls.virginia.gov · law.lis.virginia.gov · dhcd.ar.virginia.gov · fema.gov

WashingtonOfficial source

Residential code: 2021 International Residential Code with Washington amendments (Washington State Residential Code, part of the State Building Code)
How it applies: Statewide minimum, local amendments allowed
In effect since: March 15, 2024
Coming next: 2024 IRC with Washington amendments scheduled to take effect May 3, 2027 (final adoption targeted for October 16, 2026)
Code agency: Washington State Building Code Council (SBCC)
Who enforces it: Enforced by cities and counties.
Adopted by: WAC 51-51 (State Building Code Adoption and Amendment of the International Residential Code)
Good to know: Washington uses the 2021 IRC with state amendments, including a separate state energy code. The 2024 IRC is scheduled to take effect May 3, 2027.

Sources: sbcc.wa.gov · sbcc.wa.gov · fema.gov · mitek-us.com

West VirginiaSecondary source

Residential code: 2018 International Residential Code with exceptions (West Virginia State Building Code, 87CSR4)
How it applies: Statewide, applies only where locally enforced
In effect since: August 1, 2022
Code agency: West Virginia State Fire Commission / State Fire Marshal
Who enforces it: The State Building Code applies only in counties and cities that adopt it; those jurisdictions enforce it.
Adopted by: W. Va. Code R. § 87-4 (State Building Code)
Good to know: West Virginia's state code is based on the 2018 IRC but only applies where your county or city has adopted it. Ask your county whether building permits are required.

Sources: firemarshal.wv.gov · firemarshal.wv.gov · law.cornell.edu · law.cornell.edu · fema.gov

WisconsinOfficial source

Residential code: Wisconsin Uniform Dwelling Code (Wis. Admin. Code SPS 320-325), the state's own code, not the IRC
How it applies: Statewide, mandatory everywhere
Code agency: Wisconsin Department of Safety and Professional Services (DSPS)
Who enforces it: Applies to one- and two-family homes built since June 1, 1980. Municipalities with delegated authority issue permits and inspect; elsewhere a DSPS-appointed county inspector does. Local rules may not be stricter or looser than the UDC.
Adopted by: Wis. Admin. Code chs. SPS 320-325 (Wis. Stat. §§ 101.60-101.66)
Good to know: Wisconsin uses its own Uniform Dwelling Code instead of the IRC, so some IRC-based guidance may not match Wisconsin rules. Deck, stair and footing details should be checked against the UDC.

Sources: dsps.wi.gov · Dsps.Wi.Gov · fema.gov · mitek-us.com

WyomingSecondary source

Residential code: No statewide residential code; cities and counties adopt their own (often a recent IRC)
How it applies: Local adoption (no statewide residential code)
Code agency: None for residential construction
Who enforces it: Cities and counties adopt and enforce their own codes; areas that have not adopted a code may have no building permits or inspections.
Good to know: Wyoming has no statewide house code. Your city or county sets the rules, and places that haven't adopted a code may not require building permits.

Sources: fema.gov · mitek-us.com

Frequently Asked Questions

What building code does my state use?

Most states use an edition of the International Residential Code for houses, sometimes with state amendments. Find your state in the table above; your local building department can confirm the edition and any local changes for your address.

Is the IRC the law everywhere?

No. The IRC is a model code. It becomes law only when a state or local government adopts it, and some states leave adoption to cities and counties. A few rural areas have no residential code enforcement at all.

How often do building codes change?

The ICC publishes a new IRC edition every three years (2018, 2021, 2024). States adopt them on their own schedules, so a state can be one or two editions behind.

Which code applies if my permit was issued before a new edition took effect?

Generally the code in effect when the permit application was filed or issued, but the transition rules are set by your state or town. Ask your building department if you’re near a change.

Do I need a permit for a deck, patio or retaining wall?

Decks attached to the house or over a set height usually do; ground-level patios usually don’t; retaining walls over a set height or holding back a load do. The exemptions are in your adopted code’s permit section; see our state guides for walls and frost depth.

More state guides: Frost line depth · 811 dig laws · Retaining wall permits · Contractor licensing · Contractor deposit limits · Planting zones · Mechanics lien deadlines · Workers’ comp · Frost dates · Drainage laws · All state guides · Free calculators

Last checked November 1, 2026 against official state and local sources for all 51 entries. Rules change; your state agency or local building department has the final word. Spot something out of date? Email info@muthlerlandscaping.com and we’ll fix it.

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Cite as: Muthler Landscaping & Construction, “Which Building Code Does Your State Use? Residential Codes by State,” https://muthlerlandscaping.com/state-guides/building-codes/ (last checked November 1, 2026).

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