Building an ADU in San Diego requires a building permit, and depending on your property, may also involve zoning review, utility connections, and school or impact fees. California's ADU laws have streamlined much of the process, most compliant ADUs must be approved or denied within 60 days of a complete application, but "streamlined" is not the same as "no rules." Knowing the requirements before you design saves months.
Accessory dwelling units are one of the smartest ways San Diego homeowners add living space, house family, or generate rental income. The state has made them far easier to build than they were a decade ago. Still, the permit stage is where unprepared projects stall, usually because the design didn't account for a requirement that was knowable from day one.
This guide explains what ADU permits involve in San Diego, roughly how long they take, and how to keep your project moving.
Do You Need a Permit to Build an ADU in San Diego?
Yes. Every ADU requires a building permit, and the plans must show compliance with building code, zoning, and California's ADU regulations. What's changed in recent years is how the process works, not whether you need it:
- State law now requires cities to approve or deny a complete ADU application within 60 days.
- Many jurisdictions offer pre-approved or standard ADU plans that move faster.
- Certain owner-occupancy and parking requirements have been relaxed statewide.
The takeaway: the path is more predictable than it used to be, but you still need complete, code-compliant plans, and that's where a design-build contractor earns their keep. See our ADU regulations overview for the rules that shape what you can build.
Types of ADUs and How Permitting Differs
Not all ADUs permit the same way. The main categories:
- Detached ADU. A standalone unit in the yard. Full building permit; setback, height, and lot-coverage rules apply.
- Attached ADU. Added onto the existing home. Building permit plus structural review for the connection.
- Garage conversion. Converting an existing garage into living space. Often faster and cheaper, but must meet habitability, egress, and sometimes parking replacement rules.
- Junior ADU (JADU). A unit up to 500 sq ft carved out within the existing home, with its own entrance. Has its own streamlined path and owner-occupancy rule.
The type you choose affects timeline, cost, and which rules apply. Our ADU types page breaks down the options, and the San Diego ADU cost guide covers the budget side.
The ADU Permit Process, Step by Step
Here's the typical path from idea to approved permit:
- Feasibility & design. Confirm your lot qualifies (zoning, setbacks, lot size) and design a compliant unit. This is where problems get solved on paper instead of at the counter.
- Plan preparation. Architectural, structural, and Title 24 energy plans, plus a site plan showing setbacks and utilities.
- Application submittal. Plans go to the city (or county for unincorporated areas). The clock starts on the review window once the application is complete.
- Plan check & corrections. The city reviews and may return comments; your team responds and resubmits. Complete first submittals mean fewer rounds.
- Permit issuance. Once approved, permits are issued and construction can begin.
- Inspections. The city inspects at key stages (foundation, framing, rough-ins, final) through completion.
A design-build contractor manages this end to end, the same team designs the compliant plans and shepherds them through plan check. See our full ADU process for how we handle it.
How Long Do ADU Permits Take in San Diego?
Plan for 2 to 6 months for design and permitting before construction, though it varies:
- Design & plan prep: 4 to 8 weeks
- City review: up to 60 days for a complete application (state-mandated), plus time for any correction rounds
- Standard/pre-approved plans: can shave weeks off the review
The most common delay isn't the city, it's incomplete plans that trigger extra correction rounds. A thorough, code-compliant first submittal is the single best way to hit the 60-day window.
Requirements & Fees to Budget For
Beyond the plans themselves, San Diego ADU projects commonly involve:
- Utility connections. Water, sewer, and electrical, sometimes a separate meter, sometimes a shared connection.
- Impact and capacity fees. ADUs under 750 sq ft are often exempt from development impact fees; larger units may owe them.
- School fees. May apply above certain square footage thresholds.
- Setback, height, and lot-coverage limits. These shape size and placement.
- Fire safety and egress. Sprinklers may or may not be required depending on the situation and jurisdiction.
Your contractor should identify which of these apply to your specific property during the feasibility phase, so there are no surprise line items later.
Frequently Asked Questions
Do I need a permit to build an ADU in San Diego?
Yes. Every ADU requires a building permit with plans showing compliance with building code, zoning, and California's ADU laws. Cities must approve or deny a complete application within 60 days, but you still need complete, code-compliant plans to start that clock.
How long does it take to get an ADU permit in San Diego?
Design and permitting typically take 2 to 6 months before construction begins. State law caps the city's review of a complete application at 60 days, but incomplete plans that require correction rounds are the most common cause of delay.
Can I convert my garage into an ADU?
Yes, garage conversions are a popular and often lower-cost ADU path. The space must meet habitability, egress, insulation, and ceiling-height requirements, and some situations require replacing the lost parking. A contractor will assess your garage before recommending it.
Are ADUs exempt from impact fees?
ADUs under 750 square feet are generally exempt from development impact fees in California, while larger units may owe them. School fees and utility connection costs can still apply. Your contractor should confirm which fees apply to your property during feasibility.
Thinking About Building an ADU in San Diego?
The permit stage isn't the scary part, it's the predictable part, as long as your plans are complete and compliant from the first submittal. The homeowners whose ADU projects go smoothly are the ones who designed to the rules from day one instead of discovering them at plan check.
BNC Builders designs and builds ADUs across San Diego and Escondido, handling feasibility, compliant plans, permitting, and construction as one accountable team, with 30+ years of experience and in-house 3D design. If you're considering an ADU, request a free consultation and we'll tell you what your lot allows and map out the permit path.
