Quick answer: In the City of San Diego, most single-family lots can have one ADU of up to 1,200 sq ft plus a Junior ADU of up to 500 sq ft. Side and rear setbacks are usually 4 feet or less, no parking is needed outside the Coastal Overlay Zone, and owners don’t have to live on site unless there is a JADU.
Based on City of San Diego Information Bulletin 400, revised January 2026. Rules differ in the Coastal Overlay Zone and in other cities – check your address.
Thinking about adding an accessory dwelling unit to your property? Getting an ADU permit in San Diego is one of the most important steps in the process — and it’s easier than most homeowners expect, especially with California’s recent pro-ADU legislation. Whether you’re planning a detached guest house, a garage conversion, or an in-law suite, understanding the San Diego ADU permit process upfront will save you time, money, and headaches.
Want the permit handled for you? Our ADU builders in San Diego manage City and County ADU permits as part of every build.
California has made it significantly easier to permit and build ADUs over the last few years. San Diego has followed suit with streamlined approvals and pre-approved plans in some cases. But there are still requirements, fees, and steps you must follow to stay compliant.
In this guide, you’ll learn exactly how the ADU permit in San Diego process works — from eligibility checks to inspections — so you can move forward with confidence.
What Is an ADU and Why Do You Need a Permit?
An Accessory Dwelling Unit (ADU) is a secondary residential unit on the same lot as a primary residence. It can be detached, attached, or a conversion of existing space (like a garage or basement). In San Diego, any new ADU — whether you’re building from scratch or converting an existing structure — requires a building permit before any work begins.
Skipping the ADU permit in San Diego process is not an option if you want to sell your home, refinance, or rent the unit legally. Unpermitted structures can result in fines, forced removal, and complications with property insurance. The good news is that San Diego’s permit process is well-defined, and with the right preparation, it moves faster than you might think.
Types of ADUs That Require a Permit in San Diego
- Detached ADU San Diego — a fully separate structure in the backyard
- Attached ADU — shares a wall with the main home
- Garage conversion ADU — converting an existing garage into a living space
- Junior ADU (JADU) — up to 500 sq ft, typically within the main home
- Internal ADU — converting existing interior space
San Diego ADU Requirements: What You Need to Know Before You Apply
Coastal Overlay Zone: some recent City ADU rules (Housing Action Package 2.0, the 2024 code update and 2025 amendments) are not yet in effect there – check with Development Services if your property is near the coast.
Before you submit your ADU permit in San Diego application, your project must meet the city’s zoning and development standards. These rules govern how big your ADU can be, where it can be placed, and what utilities it must include.
San Diego ADU Size Limits
San Diego ADU size limits follow California state law. Here’s a quick breakdown:
- New detached or attached ADU: 150 to 1,200 sq ft
- Converted existing space (or an existing accessory structure): not held to the 1,200 sq ft cap
- Junior ADU (JADU): 150 to 500 sq ft, created within the home
Always confirm size limits with the San Diego Development Services Department, as specific lot conditions may affect what’s allowed.
San Diego ADU Setback Requirements
One of the most commonly misunderstood San Diego ADU requirements relates to setbacks — the minimum distance between your ADU and property lines. For ADUs over 16 feet tall next to a residential lot, interior side and rear setbacks are 4 feet (or the zone minimum if that is less). In a Very High Fire Hazard Severity Zone, 4 feet applies at any height. One ADU of 800 sq ft or less may sit in the front-yard setback. A JADU follows the main home’s setbacks.
Do I need parking for an ADU in San Diego?
Usually no. The City requires no parking for ADUs or JADUs outside the Coastal Overlay Zone, and you normally don’t have to replace a garage you convert. Near the beach (the Coastal Overlay Zone’s Beach Impact Area, outside transit priority areas) one space may be required, with exceptions such as ADUs of 500 sq ft or less.
Do I have to live on the property to build an ADU?
Not for an ADU – the City does not require owner occupancy. If you add a Junior ADU, the owner must live on site unless the JADU has its own bathroom facilities. ADUs can’t be rented for less than 31 days, and JADUs can’t be used as short-term rentals.
How many ADUs can I build on my lot?
On a single-family lot you can usually have one attached or detached ADU, one converted ADU and one JADU. The City’s ADU Home Density Bonus can allow more (a total of 4 on lots up to 8,000 sq ft, 5 up to 10,000 sq ft, 6 above that), with extra conditions such as deed-restricted affordable units, fire sprinklers and a Housing Commission agreement.
Are the rules different in unincorporated San Diego County?
Yes. Areas outside city limits follow County of San Diego rules, not the City’s. The County offers detached ADU plans that are about 85% complete, and its ADU fee waiver ended on January 9, 2024. Other cities in the county, such as Chula Vista and Carlsbad, each have their own ADU ordinance.
Step-by-Step: How to Get an ADU Permit in San Diego
Here is the complete ADU permit process, broken down into clear steps:
Step 1: Check Your Property’s Eligibility
Start by verifying that your lot allows an ADU. Most single-family residential lots in San Diego qualify under California state law. You can check your zoning by entering your address on the City of San Diego’s online zoning map or by contacting the Development Services Department.
Confirm utility capacity (water, sewer), confirm there are no deed restrictions, and identify whether your property is in a historic district or coastal zone, which can add review requirements.
Step 2: Develop Your Plans
You’ll need a complete set of construction drawings for your ADU permit in San Diego application. These typically include:
- Site plan showing the ADU location on the lot
- Floor plans with room dimensions and square footage
- Exterior elevations
- Foundation and structural plans
- Electrical, plumbing, and mechanical plans
Hiring a licensed architect or working with a design-build firm like NJ Design & Build ensures your drawings meet all San Diego ADU requirements from the start, reducing the chance of plan check corrections.
Step 3: Submit Your Application
You can submit your ADU permit in San Diego application online through the city’s Electronic Plan Review (ePlan) portal, or in person at the Development Services Department on Kettner Boulevard. Your submission package typically includes:
- Completed permit application form
- Two sets of construction drawings
- Title 24 energy compliance documentation
- Owner-builder form (if not using a licensed contractor)
- Applicable fees
The ADU building permit cost San Diego varies based on the size and type of ADU, but expect fees ranging from $1,000 to $5,000+ for plan check and issuance combined. Additional utility connection fees and school fees may apply.
Step 4: Plan Check Review
Once submitted, your plans go into the plan check review queue. The city will review your drawings for compliance with the San Diego ADU requirements, building codes, and zoning standards. During this phase, the plan checker may issue correction comments — questions or required changes you’ll need to address before approval.
Under state law, once your application is complete and there is already a home on the lot, the City must approve or deny it within 60 days – or it is deemed approved. Real-world timelines also depend on corrections and resubmittals. Applications using City pre-approved ADU plans get a 30-day review. Plan checkers may issue correction comments that you must address before the permit is issued.
Step 5: Permit Issuance
Once your plans are approved, you pay the remaining permit fees and receive your building permit. This is your green light to begin construction. Do not start work before this step — building without an ADU permit in San Diego is a code violation.
Step 6: Construction and Inspections
During construction, the city will require inspections at key milestones. Common inspection phases include:
- Foundation / grading inspection
- Framing inspection
- Rough electrical, plumbing, and mechanical inspection
- Insulation inspection
- Final building inspection
Once all inspections pass, the city issues a Certificate of Occupancy, and your ADU is officially legal to occupy or rent.
Read More: ADU Cost in San Diego: Complete Guide
How Long Does an ADU Permit Take in San Diego?
One of the most common questions we hear is: how long does the ADU permit take in San Diego? The honest answer: it depends on the complexity of your project and how well-prepared your application is.
- Complete application with an existing home on the lot: the City must approve or deny it within 60 days (state law)
- City pre-approved ADU plans: 30-day review
- Complex projects (historic zones, coastal, slope conditions): longer, depending on corrections and resubmittals
You can speed up the process by submitting complete, accurate plans the first time, responding quickly to plan check corrections, and working with a contractor experienced in the ADU permit process in California. Incomplete applications are the number one cause of permit delays.
ADU Permit Costs in San Diego: What to Budget
Understanding the ADU building permit cost in San Diego helps you plan your overall project budget. Fees are set by the city and depend on the ADU type, size, and scope of work.
Common ADU Permit Fee Categories
- Plan check fee: $500–$2,500
- Building permit issuance fee: $500–$2,500
- School impact fees: set by your school district – confirm the current rate before you budget
- Utility connection fees: $2,000–$10,000+ depending on meter size and service upgrades
- City Development Impact Fees: ADUs in the City pay Development Impact Fees; other fees may apply
These are typical ranges – your fees depend on size, location and utilities.
For a typical 600–800 sq ft detached ADU San Diego project, total permit and impact fees often land in the $5,000–$15,000 range before construction costs. Some homeowners are surprised by school fees and utility connection charges, so account for those early.
Note: Owner-builder ADU permit in San Diego applications are allowed, but the owner must certify they will occupy the property for at least one year after construction. Working with a licensed contractor typically streamlines the process.
Common Mistakes to Avoid During the ADU Permit Process
Even well-intentioned homeowners can run into trouble during the ADU permit in San Diego process. Here are the most common pitfalls — and how to avoid them:
- Starting construction before permit approval — this is a serious violation that can result in stop-work orders and fines.
- Underestimating setback requirements — especially for detached ADU San Diego projects where rear yard placement is common.
- Incomplete plan submissions — missing energy compliance docs or structural details cause plan check delays.
- Not accounting for utility upgrades — your existing water or sewer lateral may need upsizing to support the ADU.
- Ignoring HOA rules — even though California law limits HOA authority over ADUs, some restrictions still apply. Check your CC&Rs.
Working with an experienced team familiar with the San Diego ADU requirements from day one significantly reduces the risk of costly mistakes. NJ Design & Build offers ADU construction services and permitting assistance throughout San Diego County.
Pre-Approved ADU Plans in San Diego: A Faster Option
San Diego offers a pre-approved ADU plan program that lets homeowners skip much of the plan check process. The city has reviewed and approved a library of standard ADU designs — if your project matches one of these, your permit can be issued much faster.
This is ideal for homeowners who want a straightforward, code-compliant design without custom architectural work. Pre-approved plans are available through the City of San Diego’s Development Services website. While they don’t cover every situation (unusual lots, slope conditions, etc.), they’re a great starting point for many property owners pursuing the ADU permit process in California.
Final Thoughts
Getting an ADU permit in San Diego doesn’t have to be overwhelming. With the right preparation, a solid set of plans, and an understanding of the city’s requirements, most homeowners can navigate the process successfully. The key is starting early, doing your research, and working with professionals who know San Diego’s permitting system inside and out.
From confirming your lot’s eligibility to passing final inspections, every step of the ADU permit in San Diego process is manageable when you break it down. The result — a legal, rentable, value-adding unit on your property — is well worth the effort.
Ready to get started? Contact NJ Design & Build to speak with our team about your ADU project. We handle everything from design to permitting to construction — making the process as smooth as possible for San Diego homeowners.
Want an expert to check your lot first? Talk to our San Diego ADU builders.
FAQs
What are the ADU requirements in San Diego?
In the City of San Diego, new detached or attached ADUs can be 150 to 1,200 sq ft, a Junior ADU can be 150 to 500 sq ft, and interior side and rear setbacks are usually 4 feet or less. Every ADU needs a building permit. Confirm the details for your address with the Development Services Department.
Do I need a permit to build an ADU in San Diego?
Yes. Any ADU — detached, attached, converted, or junior — requires an ADU permit in San Diego before construction begins. Building without a permit is a code violation that can result in fines, stop-work orders, and complications when selling your home.
How long does an ADU permit take in San Diego?
Under state law, once your application is complete and there is already a home on the lot, the City must approve or deny it within 60 days – or it is deemed approved. Real-world timelines also depend on corrections and resubmittals. Applications using City pre-approved ADU plans get a 30-day review.
What are the San Diego ADU setback requirements?
For ADUs over 16 feet tall next to a residential lot, interior side and rear setbacks are 4 feet (or the zone minimum if that is less). In a Very High Fire Hazard Severity Zone, 4 feet applies at any height. One ADU of 800 sq ft or less may sit in the front-yard setback. A JADU follows the main home’s setbacks.
Can I use pre-approved ADU plans in San Diego to speed up the permit?
Yes. Applications using one of the City’s pre-approved ADU plans get a 30-day review. The plans are available through the City of San Diego’s Development Services website, but they may not fit unusual lots or slope conditions.
What is the maximum size for an ADU in San Diego?
New detached or attached ADUs can be 150 to 1,200 sq ft. Converting existing space (or an existing accessory structure) is not held to the 1,200 sq ft cap. A Junior ADU (JADU) is 150 to 500 sq ft and is created within the home.
Do I need parking for an ADU in San Diego?
Usually no. The City requires no parking for ADUs or JADUs outside the Coastal Overlay Zone, and you normally don’t have to replace a garage you convert. Near the beach (the Coastal Overlay Zone’s Beach Impact Area, outside transit priority areas) one space may be required, with exceptions such as ADUs of 500 sq ft or less.
Do I have to live on the property if I build an ADU in San Diego?
Not for an ADU – the City does not require owner occupancy. If you add a Junior ADU, the owner must live on site unless the JADU has its own bathroom facilities. ADUs can’t be rented for less than 31 days, and JADUs can’t be used as short-term rentals.
