For commercial work in Ohio, check that the code analysis cites the Ohio Building Code in OAC division 4101:1, whose rule 4101:1-1-01 incorporates the 2021 International Building Code and was last amended effective October 15, 2025, with the Ohio Mechanical Code (4101:2), Ohio Plumbing Code (4101:3), and the energy, accessibility, and referenced-standard editions Ohio lists in Chapters 13, 11, and 35. Detached one-, two-, and three-family dwellings follow the Residential Code of Ohio (4101:8), based on the 2018 IRC. AI can flag conflicts; the design professional and the certified building department decide compliance.
What does the Ohio Building Code cover?
The Ohio Board of Building Standards, in the Department of Commerce’s Division of Industrial Compliance, adopts and updates the building, mechanical, plumbing, elevator, boiler, and pressure piping codes and certifies municipal, county, and township building departments to enforce them. The Ohio Building Code (OBC) is OAC division 4101:1. Rule 4101:1-1-01 incorporates the 2021 IBC, Chapters 2 through 35 and Appendix H, and says references to the IBC, IMC, IPC, and IRC mean the Ohio Building, Mechanical, Plumbing, and Residential Codes. Its section 101.2 applies the OBC, the Ohio Mechanical Code, and the Ohio Plumbing Code to every building except listed exemptions, and sends detached one-, two-, and three-family dwellings and their accessory structures to the Residential Code of Ohio. Fire prevention and the maintenance of fire protection systems fall under the separate Ohio Fire Code (OAC 1301:7), and elevators and boilers have their own Ohio rules.
On the Ohio Administrative Code site, rule 4101:1-1-01 is effective October 15, 2025, with March 1, 2024 the prior effective date; the filed amendment kept the 2021 IBC as the base and added the substitution of “one-, two- and three-family” for “one- and two-family.” The Ohio Mechanical Code rule, also effective October 15, 2025, incorporates the 2021 IMC except Chapter 11, which now comes from the 2024 IMC. The Ohio Plumbing Code rule incorporates the 2021 IPC. Rule 4101:1-34-01 makes OBC Chapter 34 the Ohio Existing Building Code, based on the 2021 IEBC. Chapter 35 lists the referenced editions, including the 2021 IECC, ASHRAE 90.1-2019, NFPA 70-2023, and, since the October 2025 amendment, the 2021 IFC except Chapter 12, which is cited to the 2024 IFC. The Residential Code of Ohio rule 4101:8-1-01 is effective July 1, 2019 and uses the 2018 IRC as its basis. All checked October 28, 2026. Section 105.9 of rule 4101:1-1-01 says the department enforces the rules in effect on the date of the first application for plan approval, so record that date with the code basis.
Accessibility is OBC Chapter 11 as Ohio modified it in rule 4101:1-11-01. Chapter 35 lists ICC A117.1-2017 for new construction and additions and ICC A117.1-2009 for alterations and changes of occupancy, so one project can cite two editions. Energy is rule 4101:1-13-01: buildings follow the 2021 IECC or ASHRAE 90.1-2019 with Ohio’s changes, which delete the IECC commercial sections on automatic receptacle control and energy monitoring and add ACI/TMS 122.1 for thermal bridges in concrete and masonry. Houses follow RCO Chapter 11, which offers prescriptive, performance, and Energy Rating Index paths, the Ohio Home Builders Association alternative option, or the IECC. Rule 4101:1-1-01 section 102.11 gives certified building departments jurisdiction, while fire officials, health departments, and the Division of Industrial Compliance enforce the parts the rule assigns them. Section 106.2.1 requires a registered design professional’s seal except where listed. Department routing is on the Ohio page, and the model codes have their own guides: IBC, IRC, IMC, IPC, IECC, and IEBC.
Gather the code analysis, the application date, and each discipline’s Ohio references
Collect the cover sheet and code analysis with the OBC, OMC, OPC, and RCO editions cited, the architectural plans, sections, life safety plans, and door schedules, the accessibility plans and details, the structural general notes, the mechanical drawings with refrigerant and equipment schedules, the plumbing and electrical drawings, the fire protection drawings, the energy compliance documentation (COMcheck, an ASHRAE 90.1 path, or the RCO Chapter 11 path for houses), and the specifications.
Add the date of the first application for plan approval, the certified building department that will review the plans, and, for existing buildings, the scope of work and whether the project is an alteration, addition, or change of occupancy, since that decides which ICC A117.1 edition Chapter 35 points to.
Trace the Ohio rules and their editions through the set
| Review question | Sources to compare | Decision to record |
|---|---|---|
| Code edition and application date | Cover sheet, code analysis, general notes for every discipline, plan approval application | Confirm the Ohio Building Code (2021 IBC basis) is cited, not an unamended 2021 or 2024 IBC, and record the first application date that fixes the rules under section 105.9. |
| Residential Code of Ohio scope | Code analysis, building type, unit count, site plan | Check that detached one-, two-, and three-family dwellings cite the RCO (2018 IRC basis) and that other residential buildings cite the OBC. |
| Accessibility edition by work type | Accessibility plans and details, code analysis, scope of work | Confirm new construction and additions cite ICC A117.1-2017 and alterations or changes of occupancy cite ICC A117.1-2009, as Chapter 35 lists them. |
| Energy path and Ohio deletions | Energy forms, lighting and power plans, envelope details, specifications | Match the energy path to the 2021 IECC or ASHRAE 90.1-2019 with Ohio’s changes, and find notes that rely on IECC sections Ohio deleted. |
| Mechanical Chapter 11 and plumbing edition | Mechanical schedules, refrigerant notes, plumbing notes, specifications | Check that refrigeration notes follow Chapter 11 of the 2024 IMC as the OMC adopts it and that plumbing notes cite the OPC (2021 IPC basis). |
| Electrical and fire editions | Electrical notes, fire alarm and sprinkler drawings, specifications | Confirm the NEC and NFPA standard editions match Chapter 35, including NFPA 70-2023, and ask the fire official which Ohio Fire Code items apply. |
Accessible elements continue in the ICC A117.1 guide and the accessibility checklist, energy in the ASHRAE 90.1 guide, electrical sheets in the NFPA 70 guide, mechanical sheets in the mechanical drawing checklist, and the full set in the architectural drawing checklist. Pennsylvania’s statewide code is in the Pennsylvania UCC guide.
Example: a renovation and addition drawn to the latest model codes
Hypothetical example. A three-story office building in a Columbus suburb is being renovated, with a two-story addition, by a team that usually works under the 2024 I-Codes. The code analysis cites the 2024 IBC, the accessibility sheets cite ICC A117.1-2017 for both the renovated floors and the addition, the electrical plans call for automatic receptacle control citing the IECC, and the mechanical refrigerant notes cite Chapter 11 of the 2021 IMC.
The code analysis cites the 2024 IBC, while the Ohio Building Code in rule 4101:1-1-01 incorporates the 2021 IBC. The accessibility sheets cite ICC A117.1-2017 for the renovated floors, where Chapter 35 lists the 2009 edition for alterations. The receptacle control note cites an IECC section rule 4101:1-13-01 deletes, and the refrigerant notes cite 2021 IMC Chapter 11, which the Ohio Mechanical Code replaces with the 2024 chapter. Confirm the code basis with the building department and coordinate the code analysis, accessibility, electrical, and mechanical sheets.
The architect confirms the code basis and application date with the certified building department, splits the accessibility references between the addition and the altered areas, and the engineers revise the energy and refrigerant notes. The receptacle control can stay as an owner choice if the note no longer cites a deleted section. The finding is a citation conflict; the building official decides compliance.
Review an Ohio set with Groundbook
Upload the current drawings and specifications to Groundbook, and state the edition, amendments, and review scope in your instructions. The Ohio Administrative Code rules in divisions 4101:1, 4101:2, 4101:3, and 4101:8 are free on codes.ohio.gov as filed PDFs. Upload the rules you need as code files, with the model codes and standards they incorporate from copies you are licensed to use, where the license permits uploading them. See how Groundbook works with local and licensed codes.
Compare the cover sheet, code analysis, and every discipline’s general notes with the architectural, life safety, accessibility, structural, mechanical, plumbing, electrical, fire protection, and energy documents. Flag citations to unamended or newer I-Codes instead of the Ohio Building, Mechanical, Plumbing, or Residential Codes, dwellings cited to the wrong Ohio code for their type, ICC A117.1 editions that do not match new work or alterations as Chapter 35 lists them, energy notes that rely on IECC sections Ohio deleted, refrigerant notes not tied to the OMC’s Chapter 11, and NEC or NFPA editions that differ from Chapter 35. Use the supplied Ohio rules and referenced standards and cite both sources.
Groundbook links each potential finding to the note or sheet and to the Ohio rule or standard you uploaded. It compares what the documents state; it does not decide which rule or edition governs.
Document review does not certify compliance, approve plans, or replace the design professional, the certified building department, the fire official, or the Board of Building Standards.