Junior ADU (JADU) · checked Oct 18, 2026
Junior ADU fees in San Diego: $6,117–$6,282 for a 500 sq ft JADU
A junior ADU of up to 500 sq ft inside the house pays no impact fees, no school fees and no new utility connection charge under state law. What’s left in San Diego is permit and review work: building permit & plan check $5,380–$5,545, planning & zoning $737.
San Diego’s schedule
What San Diego’s documents say about junior ADUs
- General Plan Maintenance Fee — Collected once per project at application. The City’s ADU bulletin says it applies to all ADUs and JADUs.
General Plan Maintenance Fee $737.00
- Building plan check (Table 501A) — Detached ADU up to 500 sq ft: the Add/Remodel row ($3,275.45). Detached ADU over 500 sq ft: the single-dwelling row ($7,538.70). Attached ADUs and conversions up to 1,100 sq ft: $3,275.45 plus $6.51 per sq ft over 500. A converted detached accessory structure over 500 sq ft may be charged the single-dwelling row instead.
Res-SDU/DUP 1 $7,538.70 - $7,833.94 - (Single Dwelling Unit /Duplex/detached Group R-3 ADU over 500 or addition/remodel, including attached 3,000 $7,538.70 $3.82 $7,833.94 $3.93 ADU/JADU over 1,100 SF)
Res-SDU/DUP Add/Remodel 1 $3,275.45 - $2,077.66 - (Residential-Single Dwelling Unit/Duplex Addition/Remodel, including attached ADU/JADU to 1,100 SF 500 $3,275.45 $6.51 $2,077.66 $4.16 and detached ADU up to 500 SF)
- Building inspection (Table 501A) — Collected at permit issuance, from the same rows as plan check.
Res-SDU/DUP 1 $7,538.70 - $7,833.94 - (Single Dwelling Unit /Duplex/detached Group R-3 ADU over 500 or addition/remodel, including attached 3,000 $7,538.70 $3.82 $7,833.94 $3.93 ADU/JADU over 1,100 SF)
Res-SDU/DUP Add/Remodel 1 $3,275.45 - $2,077.66 - (Residential-Single Dwelling Unit/Duplex Addition/Remodel, including attached ADU/JADU to 1,100 SF 500 $3,275.45 $6.51 $2,077.66 $4.16 and detached ADU up to 500 SF)
We model a junior ADU as a conversion of space inside the home, using the same schedule lines as an ADU. Where the City charges a JADU less, that’s noted above.
Line by line: junior ADU vs new detached ADU at 500 sq ft
Law in force today. The detached column is for comparison only.
| Fee | Junior ADU, 500 sq ft | New detached ADU, 500 sq ft |
|---|---|---|
| Planning & zoning | ||
| General Plan Maintenance Fee | $737 | $737 |
| Building permit & plan check | ||
| Mapping Fee | $11 | $11 |
| Building plan check (Table 501A) | $3,275 | $3,275 |
| Building inspection (Table 501A) | $2,078 | $2,078 |
| Water/sewer plan check (no meter change) | May apply$165 | May apply$165 |
| Fee collection (other agencies) | $16 | $16 |
| Impact fees | ||
| Development Impact Fees (DIF) | $0 | $0 |
| School district fee | ||
| School fee (district; statewide cap shown) | Exempt | Exempt |
| Modeled total | $6,117–$6,282 | $6,117–$6,282 |
State law
The rules for a junior ADU
One per single-family lot, inside the house (an attached garage counts), up to 500 sq ft with an efficiency kitchen. No extra parking; owner occupancy only if it shares a bathroom.
Gov. Code §66313(d)
“Junior accessory dwelling unit” means a unit that is no more than 500 square feet of interior livable space in size and contained entirely within a single-family residence.
Gov. Code §66333(a)
Limit the number of junior accessory dwelling units to one per residential lot zoned for single-family residences with a single-family residence built, or proposed to be built, on the lot.
Gov. Code §66333(d)
For purposes of this subdivision, enclosed uses within the residence, such as attached garages, are considered a part of the proposed or existing single-family residence.
Gov. Code §66333(f)
Require the permitted junior accessory dwelling unit to include an efficiency kitchen
Gov. Code §66334(a)
A junior accessory dwelling unit ordinance adopted pursuant to Section 66333 shall not require additional parking as a condition to grant a permit.
Gov. Code §66333(b)
Owner-occupancy shall not be required if the junior accessory dwelling unit has separate sanitation facilities, or if the owner is another governmental agency, land trust, or housing organization.
Quoted from Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab), checked Oct 18, 2026.
FAQ
Questions about junior ADUs in San Diego
How much are junior ADU fees in San Diego?
Our model of San Diego’s official schedules comes to $6,117–$6,282 for a 500 sq ft junior ADU, compared with $6,117–$6,282 for a new detached ADU of the same size.
Do junior ADUs pay impact or school fees?
No. State law bars impact fees on a junior ADU of 500 sq ft or less (Gov. Code §66311.5(c)(1)), and school fees apply only when a project adds more than 500 sq ft of assessable space (Ed. Code §17620; Gov. Code §66311.5(c)(3)).
Can I build a junior ADU and an ADU on the same lot?
Yes. On a single-family lot, state law requires cities to approve one ADU and one junior ADU, plus a detached ADU of up to 800 sq ft (Gov. Code §66323(a)).
Do I have to live on the property?
Only if the junior ADU shares a bathroom with the main house. With its own bathroom, no owner-occupancy rule applies (Gov. Code §66333(b)).
Not modeled yet
What these totals leave out
- Water and sewer capacity fees (per EDU, Public Utilities) and County Water Authority meter fees aren’t modeled.
- State strong-motion (SMIP) and building standards fees are small valuation-based state fees and aren’t shown.
- The 2.5-hour DIF assessment review, lead hazard fee (pre-1978 homes only), storm water and express fees aren’t included.
- Projects with more than one ADU also pay the Regional Transportation Congestion Improvement Program fee.
More
Keep going
Sources
Official sources
Every figure comes from these documents; each line’s quoted text is on the San Diego page.
- City of San Diego Development ServicesInformation Bulletin 501: Fee Schedule for Construction Permits – Structures (opens in new tab)
- City of San Diego Development ServicesInformation Bulletin 400: Accessory Dwelling Unit / Junior Accessory Dwelling Unit (opens in new tab)
- City of San Diego City PlanningPublic Spaces: Development Impact Fee FAQ (opens in new tab)
- California State Allocation Board (Department of General Services, OPSC)State Allocation Board item: 2026 adjustment to the Level I developer fee (meeting of January 28, 2026) (opens in new tab)
- California Legislative Information (leginfo.legislature.ca.gov)Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab)
- HCD via data.ca.govHousing Element Annual Progress Report (APR) data, Table A2: ADU building permits by year (opens in new tab)