Which building code edition will my ADU MEP plans be checked against?

The edition in effect on the date your building permit application is submitted. The 2025 California Building Standards Code took effect statewide on January 1, 2026, and under Health and Safety Code section 18938.5 applications submitted on or after that date must comply with it. Applications received on or before December 31, 2025 stay under the 2022 edition, subject to local rules on how long an application remains active.

The codes your MEP sheets reference

Title 24 includes the codes cited on MEP sheets: the California Residential Code (Part 2.5), Electrical Code (Part 3), Mechanical Code (Part 4), Plumbing Code (Part 5), Energy Code (Part 6) and Green Building Standards Code, known as CALGreen (Part 11). The California Energy Commission states that the 2025 Energy Code applies to permit applications submitted on or after January 1, 2026, and that those projects must use 2025 compliance software and documents.

Local timing rules

• Application expiration. San Bernardino County, for example, let pre-2026 applications use the 2022 code only if the permit was obtained before July 1, 2026; an expired application must be resubmitted under the 2025 code.
• Submittal date only. The same county states that the code edition is determined solely by the date the application is submitted to Building and Safety, not by approval dates from other departments.
• Local amendments. The Building Standards Commission notes that cities and counties may adopt generally more restrictive local amendments, which must be filed with the state before they take effect. Your city's version may differ from the state text.
• Pre-approved plans. HCD's ADU Handbook notes that plans used for the 30-day pre-approved review must be valid within the current triennial code cycle.

Why the edition matters on MEP sheets

• The cover sheet and notes should cite the editions that apply to your application. Outdated references can draw a correction.
• The Title 24 report must be run in the software version for that code cycle, and the equipment on the mechanical schedule should match it.
• If your application expires and you reapply under a newer code, expect to update the MEP sheets and the energy report.

If your project straddles a code change

1. Write down the date your application was accepted and keep the intake receipt.
2. Ask the department how long the application stays active and what keeps it alive.
3. Tell every designer which edition applies so the whole set matches.

What this means for your MEP plans

Tell your designer when you plan to submit. MEP Plans USA prepares MEP plans and Title 24 reports for California ADUs referencing the code edition for your application date, with a standard turnaround of 5 business days. See what changed in the 2025 Energy Code and Title 24 reports. Effective dates and expiration rules vary locally, so confirm with your building department.

Sources: dgs.ca.gov, energy.ca.gov, lus.sbcounty.gov, hcd.ca.gov.