Building an ADU in San Diego in 2026: Rules, Permits, Sizes & Costs
Last updated: October 2026
Maintained by IL Total Design & Build
CSLB #1058676
California sets the ADU baseline, but your real answer depends on the property. San Diego homeowners still need to check the local jurisdiction, lot, existing structures, utilities, fire conditions, Coastal Zone status, and the kind of ADU they want to build.
Quick Answer: Can You Build an ADU in San Diego?
Many residential properties can. State law gives homeowners strong ADU rights, but it does not make every lot or every ADU design identical.
- Qualifying single-family properties can receive multiple State-protected ADU/JADU unit types.
- Size rules now use interior livable space for key State-law limits and fee thresholds.
- New ADU applications now receive a 15-business-day completeness determination, which is different from full permit approval.
- City of San Diego, unincorporated County, and incorporated cities each have their own implementation details.
- Coastal, fire, hillside, utility, access, and existing-structure conditions can change the practical design.
What Types of ADUs Can You Build?
You do not need to choose a type before the property is reviewed, but these are the main paths homeowners compare.
Detached ADU
A separate backyard or side-yard home. It gives the most independence but needs its own building footprint, utilities, access, and site work.
Attached ADU
New living space connected to the primary home. It can work well where the lot has limited detached building area.
Garage Conversion
Uses an existing garage or accessory structure. The footprint already exists, but structure, moisture, ceiling height, fire, and utility conditions still matter.
JADU
A Junior ADU is no more than 500 sq ft of interior livable space and stays within a qualifying single-family residence.
Second-Story / Above-Garage ADU
Builds up instead of using more yard. It can preserve outdoor space, but structural engineering and stair access become major design questions.
Conversion ADU
Creates an ADU from qualifying existing space. State law treats conversions differently from a new detached building in several size and setback rules.
What Changed for ADUs in 2026?
SB 543
Key ADU size and fee rules now use interior livable space. It also created the 15-business-day completeness check for ADU/JADU applications.
AB 462
For qualifying coastal ADU/JADU projects, a complete Coastal Development Permit application has a 60-day action deadline. It did not remove the Coastal Act.
AB 1332
Qualifying detached-ADU applications using preapproved or identical previously approved plans have a separate 30-day approve-or-deny rule.
AB 2533
Creates added protection for permits to legalize certain unpermitted ADUs/JADUs built before 2020, subject to health and safety findings.
City of San Diego 2025 amendments
Outside the Coastal Overlay Zone, current City rules now align more closely with State unit combinations and include updated bonus, fire, and separate-sale provisions.
Separate-sale programs
AB 1033 is local-option law. The City of San Diego and unincorporated County have adopted separate-sale programs, but their local rules are not the same.
San Diego ADU Size Rules
One of the easiest mistakes is treating 800, 850, 1,000, and 1,200 sq ft as if they all mean the same thing. They do not.
| Rule | 2026 State baseline | Why it matters |
|---|---|---|
| 800 sq ft protected ADU | State law protects the ability to create at least an 800 sq ft ADU in qualifying situations, including relief from some local development standards where necessary. | This is a State-protected floor, not the universal local maximum. |
| 850 sq ft studio / 1-bedroom | A local maximum cannot be set so low that it prevents at least 850 sq ft of interior livable space. | This limits how restrictive a local unit-size cap can be. |
| 1,000 sq ft, more than 1 bedroom | A local maximum cannot prevent at least 1,000 sq ft of interior livable space. | Bedroom count can change the minimum size a local ordinance must allow. |
| 1,200 sq ft | Many local ordinances, including the City of San Diego, allow detached ADUs up to 1,200 sq ft. | It is a common local maximum, not a universal State maximum for every ADU type. |
| JADU | No more than 500 sq ft of interior livable space. | JADUs follow a separate set of rules and stay within a qualifying single-family residence. |
One square-foot number does not control every ADU rule or fee.
California HCD says interior livable space includes bedrooms, bathrooms, kitchens, laundry rooms, closets, and interior stairs. The City of San Diego's building-permit fee schedule uses a different area concept that can include exterior wall thickness and some projections. That means the regulated ADU size and the square footage used for a permit-fee calculation may not be identical.
For the detailed 2026 measurement changes, see SB 543 and San Diego ADUs.
Setbacks and Height
For many new ADUs, State law limits required side and rear setbacks to 4 feet. A qualifying ADU created inside an existing structure, or a replacement in the same location and dimensions, can receive different setback treatment. A front-yard rule cannot be used to block an otherwise State-protected 800 sq ft ADU when that relief is required by State law.
Height is also not one number. State law protects at least 16 feet for a detached ADU, with higher minimum allowances in specified transit and multifamily situations. Attached ADUs follow a separate rule. Coastal, fire, building-code, and local zoning requirements still matter.
How Many ADUs Can You Build?
On a qualifying single-family lot, State law requires local agencies to allow combinations that can include one converted ADU, one JADU, and one newly constructed detached ADU. The exact project still has to meet the conditions for those unit types.
On an existing multifamily site, State law can allow conversion ADUs from qualifying non-livable space and up to 8 detached ADUs, capped by the number of existing multifamily units. Local rules can add implementation details but cannot erase the State-protected categories.
City of San Diego bonus units are a separate program.
The Home Density Bonus Program has its own current eligibility, affordability, fire-access, and location rules. Do not use an old fixed “4, 5, or 6 ADUs by lot size” chart as the current 2026 rule.
Parking
When parking may be required, State law caps it at one space per ADU. Several exemptions apply, including qualifying transit locations. Replacement parking is not required when existing parking is converted or removed for an ADU under State law.
Parking is only one part of feasibility. Access, utility routing, fire apparatus needs, grading, and the position of the existing home can matter more on a tight lot.
ADU Design and Permitting
A good permit package starts before drafting. Our ADU design and permitting work starts by confirming the property conditions that control the design.
Feasibility and site reviewConfirm jurisdiction, zoning, overlays, existing buildings, access, utilities, fire conditions, and the ADU type that fits the property.
DesignLay out the unit around the State size rules and the local site's real buildable area.
Engineering and energy documentationStructural, civil, energy, fire, and utility work are added as the project requires them.
Permit packagePrepare plans, calculations, forms, and supporting documents for the local agency's completeness review.
Agency review and correctionsRespond to review comments, coordinate outside agencies where needed, and obtain permit issuance.
Construction and inspectionsBuild the approved scope, complete required inspections, and obtain final approval / occupancy documentation.
For newly constructed detached ADUs, California Energy Code solar requirements generally apply. Conversions and ADUs built as additions to existing buildings do not always follow the same solar requirement, so project type matters.
How Long Does an ADU Take?
The legal review clocks are only one part of the total project. Feasibility and design happen before the permit review, corrections can add cycles, and construction comes after permit issuance.
15 business days
State-law deadline for the permitting agency to determine whether an ADU/JADU application is complete and give written notice.
Separate approval clock
A completed qualifying application has a separate approve-or-deny timeline. This is not the same as the 15-day completeness check.
30-day preapproved-plan rule
Qualifying detached ADU applications using a valid preapproved or identical previously approved plan have a separate 30-day rule.
The City of San Diego also publishes estimated first-review service targets for building permits by project complexity. Those are operating targets, not guarantees, and they should not be confused with the State legal deadlines.
City of San Diego vs. Unincorporated San Diego County
| Topic | City of San Diego | Unincorporated San Diego County |
|---|---|---|
| Permitting agency | City of San Diego Development Services | County Planning & Development Services |
| Single-family State unit combinations | Outside the Coastal Overlay Zone, current City rules allow a JADU, a converted ADU, and a detached or attached ADU when the project qualifies. | County guidance applies the State-protected ADU/JADU framework to qualifying residential sites. |
| Multifamily | Current City rules allow up to 8 detached ADUs on qualifying existing multifamily sites, capped by the number of existing units, plus qualifying conversions. | County PDS-611 also allows up to 8 detached ADUs on qualifying existing multifamily sites, capped by existing units, plus qualifying conversions. |
| Additional bonus program | Yes. The City has a separate Home Density Bonus Program with affordability and location requirements. | No City-style Home Density Bonus Program. |
| Utilities | Project review can include water/sewer and other utility coordination. | PDS-611 specifically tells applicants to check separate connection, service, and metering requirements with the serving utility. |
| Separate sale | City has adopted an ADU condominium-sale program, with Coastal Overlay Zone status requiring a separate check. | County has adopted a separate-sale program and added local sale requirements effective Sept. 18, 2026. |
Coastal Zone ADUs
The Coastal Zone follows mapped legal boundaries, not a simple “west of I-5” rule. Coastal projects can involve a Local Coastal Program, Coastal Development Permit path, bluff or flooding issues, public-access rules, habitat conditions, and other site-specific review.
AB 462 sets a 60-day action deadline for a complete qualifying Coastal Development Permit application. It does not mean the entire ADU project will be designed, permitted, and construction-ready in 60 days.
See the dedicated guide to Coastal ADU permits in San Diego for the City/Coastal Commission distinction and 2026 guidance.
What Does an ADU Cost in San Diego?
There is no honest single average that fits a garage conversion, a ground-up detached ADU, and a second-story ADU. The major cost drivers are unit type, size, existing conditions, utilities, grading, access, structural work, finishes, coastal/fire requirements, and permitting.
| City fee category | Plan check | Inspection | Derived base total |
|---|---|---|---|
| Detached Group R-3 ADU over 500 sq ft, SDU/Duplex category | $8,085.26 | $8,401.90 | $16,487.16 |
| Attached ADU/JADU up to 1,100 sq ft or detached ADU up to 500 sq ft, Add/Remodel category | $3,512.92 | $2,228.29 | $5,741.21 |
These are fee-schedule categories, not all-in permit quotes. Water/sewer, school, fire, impact, General Plan Maintenance, addressing, mapping, hourly review, and other charges can apply. Source: City of San Diego Information Bulletin 501.
For construction budgeting, see the separate 2026 San Diego ADU cost guide.
What San Diego ADU Data Tells Homeowners
The local numbers show why parcel-level feasibility matters more than a generic “ADUs are allowed” answer.
2,285
ADU homes permitted by the City of San Diego in 2024, the highest single-year total reported.
26%
Share of all City homes permitted in 2024 that were ADUs, up from 7% in 2018.
98%
Share of City ADU projects permitted in 2021–2024 that contained only one to three ADU homes.
Sources: City of San Diego 2024 Annual Report on Homes and City ADU Regulations Amendment Planning Commission presentation.
Legal eligibility is not the same as practical buildability.
From 2021–2024, the City's RS-1-7 zone produced 84% of the State-required ADUs reported in RS zones while representing 42% of RS-zoned acreage. RS-1-8 represented 22.2% of RS acreage but only 0.1% of those ADUs. Zoning alone does not explain every project, but the contrast shows why lot pattern, existing development, access, and other site conditions matter.
Can You Sell an ADU Separately?
Sometimes. AB 1033 lets local jurisdictions opt into separate condominium sale. The City of San Diego and unincorporated County have adopted local programs, but their implementation differs. City Coastal Overlay Zone status and the rules of other incorporated cities must be checked separately.
See selling an ADU separately in San Diego under AB 1033 for the mapping, lender-consent, County sale-rule, and homeowner-occupancy details.
Financing and Property Taxes
Financing choices can affect cash flow, lender requirements, and future separate-sale plans. See how to finance an ADU in San Diego for the main loan paths.
New ADU construction can also change the property's assessed value without automatically meaning the entire existing home is reassessed. See San Diego ADU property taxes for the separate tax explanation.
Choosing the Right ADU Type
| ADU type | Yard impact | Independence | Structural complexity | Common homeowner fit |
|---|---|---|---|---|
| Detached | Uses new yard footprint | High | New foundation + full new structure | Rental, family housing, long-term independent unit |
| Attached | Uses expansion area next to home | High | Addition + connection to existing structure | Lots with limited detached area |
| Garage conversion | Usually no new building footprint | Medium to high | Existing-shell conversion | Owners who can give up or replace garage use |
| JADU | No separate building footprint | Lower | Interior conversion / reconfiguration | Compact family or rental space inside the home |
| Second-story / above garage | Preserves more ground-level yard | High | Highest structural coordination of the common types | Land-constrained lots where building up makes sense |
ADU Rules by City & Neighborhood
Use these cards as a fast starting point, not as a parcel determination. State law sets the floor, but local ordinances, Coastal Zone status, fire rules, overlays, and private restrictions can change the project.
City of San Diego
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | 150–500 sq ft of interior livable space; owner-occupancy generally applies. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | Outside the Coastal Overlay Zone, current City rules allow 1 JADU, 1 converted ADU, and 1 detached or attached ADU on a qualifying single-family site. Bonus ADUs use separate program rules. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Coastal Overlay Zone rules differ. The City's 2025 ADU amendments are not yet fully effective there. |
Local notes: City rules changed in 2025. The Home Density Bonus Program can allow additional ADUs when current location, affordability, fire-access, and program requirements are met. Use Information Bulletin 400 and the current City regulatory page before fixing a unit count.
La Jolla
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | 150–500 sq ft of interior livable space; owner-occupancy generally applies. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | City of San Diego rules apply, but current Coastal Overlay Zone implementation must be checked separately. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Check the exact parcel and project. Coastal Overlay Zone rules apply, and some newer City ADU amendments are not yet effective there. |
Local notes: La Jolla is within the City of San Diego, but Coastal Overlay Zone rules can change the permitting path, setbacks, hazards review, and which newer City ADU amendments apply.
Carmel Valley
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | 150–500 sq ft of interior livable space; owner-occupancy generally applies. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: A City of San Diego neighborhood under the Carmel Valley Precise Plan . City ADU rules apply, but HOA / planned-community design review is common here and can govern materials, color and placement. Check your CC&Rs early.
Scripps Ranch
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | 150–500 sq ft of interior livable space; owner-occupancy generally applies. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: City of San Diego ADU rules apply. Many Scripps Ranch communities have active HOAs with architectural review and larger lots, both shape what you can build. Confirm CC&Rs alongside city rules.
Unincorporated County
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | Qualifying single-family sites may add an ADU and JADU. Existing multifamily sites can qualify for up to 8 detached ADUs, capped by the number of existing units. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Only relevant to parcels within the mapped Coastal Zone; verify the exact property. |
Local notes: County PDS-611 is the current starting point. It also directs applicants to the serving utility for separate connection, service, or metering requirements rather than treating separate meters as universal.
Rancho Santa Fe
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | Unincorporated County rules apply, plus private Rancho Santa Fe Covenant review where applicable. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Much of Rancho Santa Fe is unincorporated County. Where the Covenant applies, private Art Jury / design review can affect appearance and siting even when the ADU is allowed under public zoning rules.
Del Mar
| Max detached ADU | 850 sq ft (1-bed) / 1,000 sq ft (2+ beds) |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Parcel- and project-specific. Coastal Act, Local Coastal Program, and permitting-authority rules must be checked. |
Local notes: Allowed in all residential zones except RM-South . Smaller size caps and tight height limits in sensitive areas make design expertise essential here. ADU square footage counts toward the lot's floor-area ratio (FAR).
Solana Beach
| Max detached ADU | 850 sq ft (studio/1-bed) / 1,000 sq ft (2+ beds) |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Confirm the current permitting authority. Coastal Commission 2026 guidance identifies Solana Beach as an uncertified LCP jurisdiction. |
Local notes: Coastal rules are central here. Because Solana Beach does not have a fully certified Local Coastal Program, confirm whether the City or Coastal Commission is the permitting authority for the specific project.
Encinitas
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Parcel- and project-specific. Coastal Act, Local Coastal Program, and permitting-authority rules must be checked. |
Local notes: Encinitas offers permit-ready ADU resources. Coastal-zone parcels still require a separate coastal-rule check, and current plan, fee, and permit treatment should be confirmed before design.
Oceanside
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Parcel- and project-specific. Coastal Act, Local Coastal Program, and permitting-authority rules must be checked. |
Local notes: Detached units up to 1,200 sq ft; JADUs up to 500 sq ft. 60-day building-permit review; rentals must be 30+ days (no short-term rentals).
Carlsbad
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Parcel- and project-specific. Coastal Act, Local Coastal Program, and permitting-authority rules must be checked. |
Local notes: Carlsbad updated its ADU ordinance (size, parking and unit limits) to match recent state law including SB 1211 and AB 2533. Sizes and heights follow the state baseline; large coastal areas require a CDP.
Coronado
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Parcel- and project-specific. Coastal Act, Local Coastal Program, and permitting-authority rules must be checked. |
Local notes: Coastal requirements and historic / design context can affect individual properties. Confirm the mapped Coastal Zone status and the permit path for the exact parcel.
Imperial Beach
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Parcel- and project-specific. Coastal Act, Local Coastal Program, and permitting-authority rules must be checked. |
Local notes: Coastal rules can apply to ADUs in Imperial Beach. Verify the parcel, current Local Coastal Program requirements, and project-specific permit path before design.
Chula Vista
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: County's second-largest city. State baseline applies; many eastern master-planned communities have HOAs and design review that add requirements. Confirm CC&Rs in addition to city rules.
Escondido
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Inland city following the state baseline. Larger and semi-rural lots can support bigger detached ADUs where lot coverage and FAR allow.
El Cajon
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Inland East County city; state baseline applies. Confirm El Cajon's local size/height specifics for your zone.
La Mesa
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: State baseline applies. Hillside lots and older neighborhoods can affect siting and access, worth a feasibility check.
Lemon Grove
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Small East County city; state baseline applies. Confirm current local specifics for your parcel.
Santee
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Inland city following the state baseline. Some areas have HOAs and floodplain considerations, confirm before design.
San Marcos
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: North County inland city; state baseline applies. Hillside and planned-community areas may add design review.
Vista
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: North County inland city following the state baseline. Confirm Vista's local specifics for your zone.
Poway
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Known as "the City in the Country." State baseline applies, but large semi-rural lots and the Rancho/RR zones can allow bigger detached ADUs, and may carry additional rural design and access standards.
National City
| Max detached ADU | Up to 1,200 sq ft |
|---|---|
| Max attached ADU | Local percentage limits may apply; State law still protects the minimum ADU size that must be allowed. |
| Junior ADU (JADU) | Up to 500 sq ft of interior livable space; local and building-code requirements still apply. |
| Height | State minimum height protections start at 16 ft, with higher allowances in specified transit, multifamily, and attached-ADU situations. |
| Setbacks | New ADUs generally use no more than 4 ft side/rear setbacks under State law; conversion/replacement and site-specific exceptions apply. |
| Parking | At most 1 space per ADU when parking may be required; State exemptions apply, and qualifying garage conversions do not require replacement parking. |
| ADUs allowed | State law can require a converted ADU, a JADU, and a new detached ADU on a qualifying single-family lot; local rules may allow more. |
| Owner-occupancy | Not required for standard ADUs; JADU owner-occupancy generally applies, subject to statutory exceptions. |
| Coastal permit | Usually not a coastal issue, but confirm the parcel and any special overlays. |
Local notes: Compact, transit-rich South Bay city, meaning parking is frequently waived (½-mile transit rule). State baseline otherwise applies.
Real San Diego ADU Projects
These completed San Diego ADU projects show how different properties can support very different solutions, from a ground-up detached ADU to an over-garage unit and a garage conversion.
Poway · 980 Sq Ft Detached ADU
North Park · 780 Sq Ft Over-Garage ADU
Convoy · 425 Sq Ft Garage Conversion ADU
See our San Diego ADU projects.
How IL Total Design & Build Handles an ADU
Feasibility
Confirm what the property can realistically support before full plans.
Design
Develop the layout, exterior, access, and site plan around the verified constraints.
Engineering coordination
Bring in the structural, civil, energy, and other technical work the project needs.
Permitting
Prepare the application, manage review comments, and coordinate required agency responses.
Construction
Build the approved scope with the design and permit set as the controlling documents.
Inspections and final
Coordinate required inspections and closeout through the final approval stage.
Not Sure What Your Property Can Support?
Tell us the address and what you want the ADU to do. We can review the jurisdiction, site constraints, likely ADU type, and next steps before you commit to full plans.
Get Your Free Feasibility CheckFrequently Asked Questions
Can I build an ADU on my San Diego property?
Many residential properties can add an ADU, but the answer depends on the jurisdiction, zoning, existing buildings, utilities, fire requirements, Coastal Zone status, and other site conditions. Start with a parcel-specific feasibility review before paying for full plans.
How large can my ADU be?
State law protects the ability to build at least an 800 sq ft ADU in qualifying situations and limits how small a local maximum can be. A local maximum cannot prevent at least 850 sq ft for a studio or one-bedroom ADU or 1,000 sq ft for an ADU with more than one bedroom. Many San Diego jurisdictions allow up to 1,200 sq ft, but local rules still matter.
What counts toward ADU square footage in 2026?
SB 543 uses interior livable space for key State ADU size rules. California HCD says interior livable space includes bedrooms, bathrooms, kitchens, laundry rooms, closets, and interior stairs. That is different from some permit-fee area calculations.
What are the setback requirements?
State law generally limits side and rear setbacks for a new ADU to 4 feet. No setback is required for a qualifying ADU created within an existing structure or a replacement built in the same location and to the same dimensions. Front setbacks, fire rules, coastal rules, and building-code separation can still affect the site.
How tall can an ADU be?
State law protects at least 16 feet for a detached ADU, with higher minimum allowances in specified transit and multifamily situations. Attached ADUs have a separate height rule. Local zoning, Coastal Zone rules, fire requirements, and the proposed ADU type still need to be checked.
Do I need parking for an ADU?
Parking is capped at one space per ADU when it may be required, and State law provides several exemptions, including qualifying transit locations. Replacement parking is not required when qualifying existing parking is converted or removed for an ADU.
Can I convert my garage into an ADU?
Often, yes. A garage conversion uses existing space and follows different size and setback rules from a new detached ADU. Building-code, fire, utility, ceiling-height, foundation, moisture, and parking conditions still need to be reviewed.
Can I build an ADU above my house or garage?
Potentially. A second-story or above-garage ADU can preserve yard space, but it adds structural engineering, stair access, height, fire, and construction-sequencing questions. The existing structure must be evaluated before design is finalized.
How long does ADU permitting take?
The State now requires a completeness determination within 15 business days. A separate approval or denial timeline applies to a completed qualifying application, and qualifying preapproved detached-ADU plans have a separate 30-day rule. Feasibility, design, corrections, outside-agency work, and construction are separate from those review clocks.
How much does an ADU cost in San Diego?
There is no reliable single average for every ADU. Cost changes with size, type, site access, grading, utilities, structural work, finishes, coastal or fire conditions, and permit fees. A garage conversion, detached ADU, and second-story ADU can have very different budgets.
Can I sell an ADU separately from the main house?
Separate sale is possible only where the local jurisdiction has implemented the State condominium-sale option and the property meets the local requirements. The City of San Diego and unincorporated County have adopted programs, but their rules differ, and Coastal Overlay Zone or other city rules can change the answer.
Are Coastal Zone ADU rules different?
Yes. The California Coastal Act still applies. Coastal permitting depends on the mapped parcel, the Local Coastal Program, the permitting authority, coastal hazards, and the project. AB 462 creates a 60-day action deadline for a complete qualifying Coastal Development Permit application, not a 60-day total project guarantee.
What is a JADU?
A Junior ADU is no more than 500 sq ft of interior livable space and is contained within a qualifying single-family residence. It can share sanitation facilities with the main home, and owner-occupancy generally applies.
What should I do before paying for full plans?
Confirm the jurisdiction, zoning, Coastal Zone status, fire constraints, utilities, existing structure, access, likely ADU type, and basic size envelope. That early feasibility work can prevent paying for a design that does not fit the property.
Official Sources & Research
Primary and institutional sources used for this October 2026 update:
- California HCD, Accessory Dwelling Unit Handbook, March 2026
- City of San Diego, Information Bulletin 400, ADU/JADU
- City of San Diego, Regulatory Updates
- City of San Diego, Information Bulletin 501, construction permit fee schedule
- City of San Diego, 2024 Annual Report on Homes
- City of San Diego, ADU Regulations Amendment Planning Commission presentation
- County of San Diego PDS-611, Accessory & Junior Accessory Dwelling Unit
- County of San Diego, ADU Zoning Ordinance Amendment / separate sale
- California Coastal Commission
SB 543 and ADUsInterior livable space, completeness review, and 2026 fee thresholds.
Coastal ADU PermitsAB 462, Coastal Development Permits, and San Diego coastal rules.
Selling an ADU SeparatelyAB 1033, condominium conversion, and local separate-sale rules.
Not legal advice. ADU rules change, local implementation varies, and site-specific conditions matter. This page is general information for San Diego homeowners, not a parcel-specific approval or legal determination. Final requirements should be confirmed for the property with the governing jurisdiction and applicable agencies. IL Total Design & Build, CSLB #1058676. Last updated October 2026.