Confirm the permit uses the 2025 California Mechanical Code, Title 24 Part 4, effective January 1, 2026 and adopted from the 2024 Uniform Mechanical Code, and that the mechanical notes do not cite the IMC or the 2021 UMC-based 2022 CMC. Then identify which agency’s amendments apply, check health care ventilation against the OSHPD basis the project follows, and confirm the refrigerant, exhaust, and energy documents agree with the mechanical schedules. AI can flag conflicts; the mechanical engineer and the authority having jurisdiction decide compliance.
What does the California Mechanical Code cover?
The California Mechanical Code is Part 4 of the California Building Standards Code, Title 24. The commission-issued errata packet’s history note describes adopting the 2024 Uniform Mechanical Code by reference, with necessary amendments, to become the 2025 CMC and repealing the 2021 edition. Its adopting agencies include the Building Standards Commission, the Division of the State Architect structural safety program, HCD, OSHPD, and the State Fire Marshal, with an Energy Commission change in Chapter 12.
The California Building Standards Commission states that the 2025 Title 24 was published July 1, 2025 with an effective date of January 1, 2026, and lists Part 4 in the 2025 edition. Its 2024 triennial cycle page says the cycle adopts the 2024 editions of the ICC and IAPMO model codes and the 2023 edition of the NEC. The CMC errata packet carries the adoption history note, and HCD’s final statement of reasons cites the 2024 UMC. The supplement links listed under the 2025 heading on the commission’s Codes page pointed to the 2022 supplements when checked, so do not cite them as 2025 supplements. Checked October 19, 2026. The code in effect when the permit application is submitted is the one that applies, cities and counties may adopt local amendments with findings filed with the commission, and the commission’s 2025 intervening cycle will publish supplements effective July 1, 2027.
Model code checks are in the UMC guide. The adopting agencies’ statements describe OSHPD basing its health care ventilation table on ASHRAE 170-2021 and the State Fire Marshal replacing its early A2L refrigerant amendments with the model code text; the ASHRAE 170 guide covers the health care standard. HCAI publishes a code application notice for the CMC on its codes and regulations page.
Gather the mechanical set and the agency context
Collect the mechanical general notes and code references, the HVAC plans, sections, and details, equipment and fan schedules, ventilation and exhaust calculations, the refrigerant schedule and safety measures, kitchen hood and exhaust drawings, smoke control or fire damper drawings, control sequences, the mechanical specifications, and the energy compliance forms. Add the code analysis that names the occupancy and agency with jurisdiction.
For health care projects, add the room ventilation schedule, because the OSHPD table drives air change, pressure relationship, and filtration checks room by room.
Trace CMC decisions through the mechanical set
| Review question | Sources to compare | Decision to record |
|---|---|---|
| Model code and edition | Mechanical general notes, specifications, cover sheet | Confirm the 2025 CMC is cited and that no sheet relies on the IMC, the 2021 UMC, or the 2022 CMC. |
| Agency with jurisdiction | Code analysis, cover sheet, Chapter 1 scope | Record which agency’s amendments apply to the building or area. |
| Health care ventilation | Room ventilation schedule, mechanical plans, air balance schedule | Check that the ventilation schedule uses the OSHPD basis the project follows and that air balance and pressure relationships match it. |
| Refrigerants | Equipment schedules, refrigerant schedule, mechanical room plans, specifications | Match the refrigerant in each system to the safety measures, detection, and room requirements the drawings show. |
| Exhaust and kitchen hoods | Exhaust fan schedule, hood drawings, roof plan, specifications | Confirm each exhaust system on the schedules is drawn with its discharge and make-up air. |
| Energy forms | Energy compliance forms, equipment schedules, control sequences | Match equipment and controls on the mechanical sheets to the California Energy Code forms. |
Energy compliance continues in the California Energy Code guide, balancing in the testing, adjusting, and balancing guide, and kitchen exhaust in the NFPA 96 guide.
Example: an IMC note on a California clinic
Hypothetical example. A tenant improvement for an outpatient surgery suite in Fresno was adapted from a set drawn in another state. The mechanical general notes cite the 2024 International Mechanical Code, the room ventilation schedule follows an older ASHRAE 170 edition, and the air balance schedule shows a procedure room at a pressure relationship that differs from the ventilation schedule.
The mechanical general notes cite the 2024 IMC instead of the 2025 CMC, the room ventilation schedule follows an older ASHRAE 170 edition than the OSHPD basis, and the procedure room pressure differs between the ventilation and air balance schedules. Confirm the code basis and the room requirements, and coordinate the notes and schedules.
The mechanical engineer revises the notes and schedules and confirms with the authority which agency rules apply to the suite. The finding is a document conflict, not an airflow result.
Review California mechanical drawings with Groundbook
Upload the current drawings and specifications to Groundbook, and state the edition, amendments, and review scope in your instructions. Add the California Mechanical Code edition the project uses from a copy you are licensed to use, where the license permits uploading it, and the jurisdiction’s published amendments. See how Groundbook works with local and licensed codes.
Compare the mechanical general notes, HVAC plans, sections, and details, equipment, fan, refrigerant, ventilation, and air balance schedules, kitchen exhaust drawings, control sequences, code analysis, energy compliance forms, and mechanical specifications. Flag a cited IMC, 2021 UMC, or 2022 CMC instead of the 2025 CMC, no stated agency with jurisdiction, health care ventilation or pressure that differs between schedules, refrigerants without the safety measures drawn, exhaust systems without discharge or make-up air, and equipment that differs from the energy forms. Use the supplied CMC and cite both sources.
Groundbook links each potential finding to the sheets and documents involved. It does not calculate ventilation rates, loads, or refrigerant quantities.
Document review does not certify compliance or approve a permit. Those remain with the mechanical engineer and the authority having jurisdiction.