How do I change my ADU's MEP plans after the permit is issued?

Submit a revision to the building department and get it approved before you build the change. Approved plans cannot be altered without the building official's authorization; San Diego processes these as construction changes, and Los Angeles tells homeowners to return to plan check if construction will vary from the approved plans. The revision shows what changed, clouded and marked, with updated calculations.

How a revision typically works

San Diego's Information Bulletin 118 is a detailed example:

• Approved plans and specifications shall not be changed, modified or altered without authorization of the building official.
• Submit only the revised or added sheets, with the revision date, description and mark in each title block, a revision summary table, and an updated title sheet narrative and sheet index.
• Cloud only the revised work and mark it with a numbered delta. Changes that are not clouded are not part of the approved change, and clouds and deltas from earlier approved changes are removed.
• Revised calculations and reports are signed and sealed by the appropriate licensed professionals.
• Additions to scope may need a separate permit, a substantial redesign may require a new application, and only one construction change can be submitted at a time.
• Approved change sheets, printed full size, are kept on site with the original plan set for inspection.

Yorba Linda similarly requires post-permit changes to follow its changes-to-approved-plans handout and rejects revisions without clouds and deltas.

MEP changes that often call for a revision

• Different HVAC or water heating equipment, especially if capacity or efficiency changes.
• Moving the outdoor condenser, panel, water heater or a bathroom.
• Adding circuits, an EV charger or a panel upgrade.
• Switching between gas and electric appliances.

Don't forget the energy report or the stamp

Equipment on the mechanical schedule should match the Title 24 compliance documents, and the Energy Commission's 2025 ADU guidance has inspectors confirm that registered documents are complete at final. An equipment swap may mean updating the energy report as well as the plans. If the original sheets were stamped, the revised sheets go back to that engineer; under B&P 6735.3 and 6735.4, an engineer is not responsible for changes they did not authorize.

Steps to follow

1. Describe the change and why it is needed before buying equipment or opening walls.
2. Have the designer revise the affected sheets and calculations.
3. Submit through the city's revision process and wait for approval.
4. Print the approved revision and keep it with the original set on site.

What this means for your MEP plans

Send MEP Plans USA the approved set and a description of the change, and we can revise the affected sheets with clouds and deltas and update the Title 24 report if you ordered one. Where your jurisdiction requires a PE stamp, it is a separately quoted add-on. See HVAC installed differently than shown, revisions included and Title 24 reports. Revision procedures vary, so confirm with your building department.

Sources: sandiego.gov, dbs.lacity.gov, yorbalindaca.gov, energy.ca.gov, bpelsg.ca.gov.