Can I draw my own MEP plans for my ADU as the homeowner?

In many cases, yes. If your ADU is a wood-frame building no more than two stories and a basement, the design exemptions in Business and Professions Code sections 5537 and 6737.1 let any person prepare the plans, including you. The harder part is producing sheets that pass plan check, and your building department can still require a licensed designer for parts of the project.

What the rules say about owner-drawn plans

• No license needed for exempt buildings. The exemption covers wood-frame single-family dwellings, small multiple dwellings and appurtenant structures within the height limit. Non-wood construction falls outside it.
• Signing. B&P 5536.1 requires people who prepare plans for others to sign them. The California Architects Board's guide says an owner drawing plans for their own exempt building is not required by statute to sign, though a building official may still require a signature.
• Local discretion. Building officials must require a licensed architect or engineer for portions that deviate from conventional framing, and the Board says they may require more where they see undue risk.

What plan check will expect from you

Owner-drawn sheets are reviewed against the same codes as professional sets. Expect the reviewer to look for:

• The electrical panel or subpanel with its rating, the circuit and outlet layout, and a load calculation where the department requires one.
• Plumbing fixture locations, types and flow rates, drain and vent routing, the sewer connection and water heater details.
• Heating, cooling and ventilation equipment with capacities, bath and kitchen exhaust, and the whole-house ventilation method.
• Title 24 energy documents that match the equipment. The California Energy Commission's 2025 ADU guidance says compliance documents must be registered with an ECC provider registry, and Yorba Linda, for example, requires the Title 24 declaration to be signed by the designer of the plans rather than the energy consultant.

Los Angeles publishes a homeowner's guide listing minimum submittal items for simple projects, including floor and plot plans and the energy certificate of compliance (CF1R). Other departments publish their own checklists.

Is it worth it?

• It can make sense for a simple conversion if you are comfortable researching code sections and working through correction rounds.
• You will answer the plan checker's comments yourself, and each round adds time.
• Your installers will build from your drawings, so unclear sheets can turn into field questions.

What this means for your MEP plans

If you would rather spend your time managing the build, MEP Plans USA prepares permit-ready MEP sheets from your architectural plans, with a standard turnaround of 5 business days and two revisions plus city plan-check corrections included. See how it works, the difference between permit-ready and design drawings, and owner-builder permits. Requirements vary by city, so confirm with your building department. This is not legal advice.

Sources: cab.ca.gov, bpelsg.ca.gov, cab.ca.gov, dbs.lacity.gov, energy.ca.gov.