Unincorporated only: This page covers the unincorporated area of San Diego County — parcels outside any city, regulated by the County Planning / Land Use Services Department. If your address is inside a city (San Diego, Chula Vista, Oceanside, Escondido, Carlsbad, El Cajon), use that city's ADU page instead.
These rules cover UNINCORPORATED San Diego County - Spring Valley, Lakeside, Ramona, Fallbrook, Alpine, Valley Center, Jamul, Julian and similar communities - not the City of San Diego or the county's 18 incorporated cities, which run their own ADU programs. Yes, you can build one: Zoning Ordinance Section 6156.x (rewritten by Ordinance No. 10986, effective April 4, 2026, and amended by Ordinance No. 11016, effective September 18, 2026) allows one new detached ADU of up to 1,200 sq ft and 25 ft in height with 4 ft side and rear setbacks, plus a conversion ADU and a 500 sq ft JADU, on any residential or mixed-use lot with a single-family home, approved ministerially by Planning & Development Services (PDS) with no hearing. Under the FY 2026-27 fee schedule (PDS-613) plan review and permit fees run about $4,400 for an 800 sq ft unit and $4,800 for 1,200 sq ft, and an ADU over 750 sq ft also pays the county park impact fee ($4,400-$6,620 depending on the community) plus parcel-based traffic and drainage fees. Six free county plan sets (600-1,200 sq ft) cut design cost, and the county is one of the first in the region to let a finished ADU be sold separately as a condominium (Sec. 6156.x.D) - now with a right of first refusal, a one-year owner-occupancy affidavit and a 30-day public listing period.
Zoning & Size Requirements [1][2][3][4]
Yes — unincorporated San Diego County allows ADUs. A detached ADU can typically be up to 1,200 sq ft under California state law and the County's zoning code.
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| Where ADUs Are Allowed | By right on any lot in a residential or mixed-use zone with an existing or proposed single-family home, and on multifamily lots, with ministerial approval under Zoning Ordinance Sec. 6156.x.B (Gov. Code 66323). A lot whose home is non-conforming, or whose zone no longer allows a house, still qualifies (Sec. 6156.x.A.23). Section rewritten by Ord. No. 10986 (N.S.), effective April 4, 2026, and amended by Ord. No. 11016 (N.S.), effective September 18, 2026. |
| Max Size (Detached) | 1,200 sq ft regardless of the main home's size (Sec. 6156.x.A.5); floor area is measured to the exterior dimensions of the outside walls (A.6). Converting an existing permitted accessory structure has no size cap as long as it stays within the existing envelope - the county's own example is a permitted 3,000 sq ft barn (A.11, PDS-611) - plus up to 150 sq ft added solely for entry and exit (B.1.a.i). |
| Max Size (Attached) | 50% of the main home's floor area, capped at 1,200 sq ft; the 50% limit does not apply to an attached ADU of up to 850 sq ft, or up to 1,000 sq ft with more than one bedroom (Sec. 6156.x.A.4). Part of the house may be converted with no size limit as long as part of it remains the main residence (PDS-611, Rev. 09/02/2026). |
| Max Size (JADU) | 500 sq ft, entirely inside the existing or proposed single-family home or its attached garage; efficiency kitchen with appliances and counter required, a separate entrance, and it may share a bathroom with the house (then an interior door to the house is required); no separate electric meter; a deed restriction is recorded (Sec. 6156.x.B.3). |
| Max Height | 25 ft for a detached ADU on a single-family lot (Sec. 6156.x.A.10) - well above the state 16-18 ft floor. The 800 sq ft state-exempt detached unit approved under 6156.x.B.1.b, and detached ADUs on a lot with an existing multifamily building, are limited to 18 ft (25 ft with a proposed multifamily building). Attached ADU: the height of the house or 16 ft, whichever is higher (ADU Handbook, p. 6). |
| Max Units | Single-family lot: one new detached ADU, plus one conversion ADU inside the house or an accessory structure, plus one JADU (Sec. 6156.x.B.1); the same allowance applies to a lot with several detached houses (A.22). Multifamily lot: conversions of non-livable space up to 25% of the existing units, plus detached ADUs - up to 8 on an existing complex (never more than the existing unit count) or 2 with a proposed complex (B.1.c-e, SB 1211). Guest living quarters cannot coexist with an ADU (6156.k). |
Setback & Parking Requirements [1][2][3][4]
Unincorporated San Diego County requires a rear setback of about 4 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | 4 ft minimum for any newly built detached or attached ADU (Sec. 6156.x.A.15); none when an existing permitted accessory structure is converted, except for fire safety, private wells and septic systems (A.13). Fire-district setbacks apply on top - much of the unincorporated county is in a high or very high fire hazard severity zone. |
| Side Setback | 4 ft minimum on the interior side; on a corner lot the exterior side must be at least 4 ft from the edge of the easement, street or property line (Sec. 6156.x.A.15-16). An ADU built above a permitted detached garage keeps the 4 ft rule only for the added space and may extend beyond the garage walls (A.14). |
| Front Setback | The zone's normal front setback applies, but an ADU may encroach into it if the setback would otherwise prevent building an ADU of 800 sq ft or smaller (Sec. 6156.x.A.17). An ADU in the front setback may not block the driveway or the home's two required parking spaces unless two replacement spaces are provided (A.18). |
| Parking Required | 1 space; tandem in the driveway and inside setbacks is fine (Sec. 6156.x.A.20). None within a half mile of public transit, in a historic district, for a conversion of the house or an accessory structure, where street permits are withheld from the ADU, with a car-share within a block, or when built with a new home (A.21). No replacement parking when a garage becomes an ADU; PDS-611 also waives the space for ADUs of 800 sq ft or less. JADU: no space, but replace converted garage spaces (B.3.h-i). |
| Owner Occupancy | Not required for ADUs (Sec. 6156.x has no requirement; AB 976 made the state ban permanent). JADUs: the county deed restriction and PDS-611 still require the owner to live in the house or the JADU (6156.x.B.3.a.iii), but Gov. Code 66333(b) as amended by AB 1154 (effective January 1, 2026) drops that where the JADU has its own bathroom, and the PDS Director's Determination of January 29, 2025 says state law prevails - raise it at the Zoning Counter. |
| Min Lot Size | None - Sec. 6156.x sets no minimum lot size for an ADU or JADU, and Gov. Code 66314(b)(1) bars one. On septic or a well, the Department of Environmental Health and Quality (DEHQ) must confirm the system can serve the house and the ADU before PDS can approve; an undersized system can be upgraded or the bedroom count reduced (Sec. 6156.x.B.2.d). |
Permit Process & Fees [5][6][7][8][9][10][11]
An ADU in unincorporated San Diego County is approved administratively — no public hearing. Review time: not published by the county (the ADU Handbook says plan review takes 'several weeks'); state law requires a completeness notice within 15 business days and a decision within 60 days of a complete application (Gov. Code 66317, as amended by SB 543). Permit fees: FY 2026-27 schedule (PDS-613, effective July 10, 2026): ADU plan review $1,940 + $0.410/sq ft and permit $1,677 + $0.564/sq ft - about $4,400 for 800 sq ft and $4,800 for 1,200 sq ft; over-the-counter ADU review is $1,128 + $0.316/sq ft. The 2019-2024 fee waiver has ended.
| Approval Process | Ministerial building permit through Planning & Development Services (PDS, 5510 Overland Ave, Suite 110) - no hearing, no discretionary review (Sec. 6156.x.B, Gov. Code 66323). Submittal follows PDS-658 (minimum plan items); the fire district signs off, and DEHQ clears the septic system or well, before approval. Unpermitted ADUs or JADUs built before January 1, 2020 use the AB 2533 path (6156.x.A.24-25): the permit cannot be denied except for health-and-safety or septic violations, no impact or connection fees apply, and PDS-738 (Substandard Structure Checklist, Rev. 6/6/2025) lists what must be fixed; a confidential third-party inspection first is optional. |
| Review Timeline | Not published by the county (the ADU Handbook says plan review takes 'several weeks'); state law requires a completeness notice within 15 business days and a decision within 60 days of a complete application (Gov. Code 66317, as amended by SB 543). |
| Permit Fees | FY 2026-27 schedule (PDS-613, effective July 10, 2026): ADU plan review $1,940 + $0.410/sq ft and permit $1,677 + $0.564/sq ft - about $4,400 for 800 sq ft and $4,800 for 1,200 sq ft; over-the-counter ADU review is $1,128 + $0.316/sq ft. The 2019-2024 fee waiver has ended. |
| Impact Fees | None for an ADU with 750 sq ft of interior livable space or less (Gov. Code 66311.5); above that, fees are charged in proportion to the main home. The county park (PLDO) impact fee for an ADU is $4,400-$6,620 by local park planning area in 2026 (Spring Valley $5,431, Lakeside $4,916, Fallbrook $5,017, Ramona $4,875, Alpine $4,896), collected at permit issuance; traffic (TIF) and drainage fees depend on the parcel (DPW estimator). School fees: an ADU under 500 sq ft adds no assessable space (66311.5(c)(3)). Pre-2020 unpermitted units legalized under AB 2533 pay no impact or connection fees (Sec. 6156.x.A.25). |
| Plan Check | Standard PDS plan check against PDS-658 (site plan with floor-area calculations for both units, fire-district and DEHQ approvals first). The six county plan sets are about 85% complete - owners fill in site-specific details using the Dwelling Unit Checklist and its Guidance; ask PDS whether a county plan set qualifies for the cheaper over-the-counter review tier. |
| Pre-Approved Plans | Yes - 6 free ADU plan sets offered since 2019 (Plans A-F: three 1,200 sq ft 2-3 bedroom models, a 1,000 sq ft 1BR/1.5BA, an 800 sq ft 1BR and a 600 sq ft 1BR), downloadable as PDF and CAD; Plans G-H (1,500-1,728 sq ft) are for single-family homes only. |
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Construction Costs [12][13][14][15]
Building an ADU in unincorporated San Diego County typically costs $250,000-$450,000 ($375-$600 per sq ft); a garage conversion runs $80,000-$200,000.
See what this means for your lot — ask San Diego County ADU builders for a quote →
Construction costs in unincorporated San Diego County track the surrounding metro market. Rural parcels can cost more because of septic, well, access and fire-hazard requirements, so treat these as planning ranges and get local bids.
| Average Build Cost | $250,000-$450,000 |
| Cost per Sq Ft | $375-$600 |
| Garage Conversion | $80,000-$200,000 |
| Prefab ADU (Installed) | $170,000-$325,000 |
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Rental Income Potential [16]
| Avg Rent (1 Bedroom) | $1,700-$2,450/mo |
| Avg Rent (2 Bedroom) | $2,050-$2,950/mo |
| Short-Term Rental | No - Sec. 6156.x.A.3 and B.3.k bar renting an ADU or JADU for a term of less than 31 days (the PDS-611 handout says 30 days; the code controls). |
| Est. Annual ROI | 5-9% gross annual yield (HUD FY 2027 Small Area FMR rents on a $250,000-$450,000 build; rural lots that need a septic upgrade or fire-access work land lower). |
Recent Law Changes
What's Changed Recently
- September 18, 2026: Ordinance No. 11016 (N.S.), adopted 5-0 on August 19, took effect - an ADU sold as a condominium now carries a right of first refusal for the tenant or co-owner on the lot (30 days to match an offer), a buyer affidavit to occupy the unit for at least one year, and a 30-day public listing on two MLS-fed websites, waivable by the PDS Director (Sec. 6156.x.D.10-12). The Board also ordered a 180-day report on enforcement, deed restrictions and raising the 1,200 sq ft size cap.
- September 2, 2026: PDS reissued handout PDS-611 (ADU & JADU Zoning Requirements) to match the reorganized Sec. 6156.x.
- July 10, 2026: the FY 2026-27 building fee schedule (PDS-613, Rev. 07/06/2026) took effect - ADU plan review $1,940 + $0.410/sq ft, permit $1,677 + $0.564/sq ft.
- April 4, 2026: Ordinance No. 10986 (N.S.), adopted unanimously March 4, took effect - Sec. 6156.x reorganized and aligned with SB 1211 (up to 8 detached ADUs on an existing multifamily lot), AB 2533 (pre-2020 amnesty with no impact fees) and AB 976 (no ADU owner-occupancy), and created the AB 1033 program allowing ADUs to be sold separately as condominiums (Sec. 6156.x.D).
- January 1, 2026: SB 543 (15-business-day completeness notice, 60-day decision, school-fee relief for units under 500 sq ft) and AB 1154 (no JADU owner-occupancy where the JADU has its own bathroom) took effect statewide; the county's JADU deed restriction has not yet been conformed.
- January 9, 2024: the county's five-year trial ADU fee waiver (plan check and impact fees, in effect since January 9, 2019) expired - full fees apply to permits issued after that date.
Tips for Building an ADU in Unincorporated San Diego County
- Spring Valley, Lakeside, Ramona, Fallbrook, Alpine, Valley Center, Jamul, Julian, Bonsall, Rainbow and the other unincorporated communities follow these County rules - not City of San Diego rules; check the PDS Property Summary Report by APN if you are unsure which side of a city line you are on
- Start with the free county plan sets (600-1,200 sq ft, PDF + CAD): they are about 85% complete, and the county has offered them since 2019 - among the earliest programs in California
- Fire sprinklers are not required in an ADU if the main house was not required to have them (Sec. 6156.x.B.2.b), but the fire protection district can impose access, hydrant and defensible-space requirements - in the backcountry talk to your fire district before you design
- On septic or a well, DEHQ must confirm capacity before PDS can approve the ADU; if the system is too small you can upgrade it or drop a bedroom (Sec. 6156.x.B.2.d) - budget for this early on rural lots
- The 25 ft height allowance (versus 16-18 ft in many cities) makes a two-story detached ADU feasible on a single-family lot; the 800 sq ft state-exempt unit is capped at 18 ft
- Built an ADU without permits before 2020? Under AB 2533 and Sec. 6156.x.A.24-25 the county cannot deny the permit for code violations unless health, safety or septic standards require the fix, and no impact or connection fees apply - use the PDS-738 checklist and consider a confidential third-party inspection first
- Selling the ADU separately takes a Tentative Parcel Map, lienholder and HOA consent, fire-district concurrence, utility notification and a condo plan recorded only after final inspection (Sec. 6156.x.D; county Condo Guidance & Checklist, Rev. 04/03/2026); JADUs cannot be sold separately
- Fee arithmetic (PDS-613, FY 2026-27): a 1,000 sq ft ADU pays $2,350 plan review + $2,241 permit = $4,591 to PDS, plus a $171 address assignment if the unit needs one, the park impact fee for your community (for example $5,431 in Spring Valley) and parcel-based TIF and drainage fees; a unit of 750 sq ft or less skips the impact fees entirely
- Cost basis: build and conversion ranges come from San Diego industry cost guides dated March-September 2026 (same basis as the San Diego, Chula Vista and Carlsbad pages); rents are HUD FY 2027 Small Area Fair Market Rents (effective October 1, 2026) for unincorporated ZIP codes - 1BR from $1,700 (Valley Center 92082) to $2,430 (Spring Valley 91978), 2BR from $2,050 to $2,940; Lakeside 92040 $2,050/$2,480, Ramona 92065 $2,080/$2,510, Alpine 91901 $2,160/$2,610
ADU Builders in San Diego County
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Cities Within San Diego County
If your property is inside one of these incorporated cities, follow that city's ADU code — not the County rules above:
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- San Diego County Zoning Ordinance Sec. 6156.x - Accessory Dwelling Unit and Junior Accessory Dwelling Unit (2026 S-141, amended by Ord. 10986 adopted 3-4-26 and Ord. 11016 adopted 8-19-26) Planning Department — Accessed 2026-09-20
- PDS-611 - ADU & JADU Zoning Requirements (Rev. 09/02/2026) Planning Department — Accessed 2026-09-20
- County ADU Zoning Ordinance Amendments and Local Criteria for the Separate Sale of ADUs (adopted 3/4/2026, eff. 4/4/2026; conditions eff. 9/18/2026) Government Data — Accessed 2026-09-20
- PDS Director's Determination - Implementing New Housing Laws Prior to Zoning Ordinance Amendments (January 29, 2025) Planning Department — Accessed 2026-09-20
- County of San Diego PDS - Accessory Dwelling Units Planning Department — Accessed 2026-09-20
- PDS-613 - Building Fee Schedule FY 26/27 (Rev. 07/06/2026, effective 07/10/2026) Planning Department — Accessed 2026-09-20
- County Dwelling Unit Building Plans (6 free ADU plan sets) Planning Department — Accessed 2026-09-20
- Separate Sale of ADUs as Condominiums - Qualifications Guidance (Rev. 04/03/2026) Planning Department — Accessed 2026-09-20
- PDS-738 - Substandard Structure Checklist (AB 2533 amnesty, Rev. 6/6/2025) Planning Department — Accessed 2026-09-20
- PDS-658 - Minimum Essential Plan Submittal Items for Single Family Dwellings and Accessory Structures Planning Department — Accessed 2026-09-20
- County Parks - Park Land Dedication Ordinance (PLDO) 2026 Accessory Dwelling Unit park impact fees Government Data — Accessed 2026-09-20
- Cost to Build an ADU in San Diego (2026), updated March 2026 | Snap ADU industry — Accessed 2026-09-19
- How Much Does an ADU Cost in San Diego? (2026 Guide), reviewed June 14, 2026 | ADUVerified industry — Accessed 2026-09-19
- ADU Cost San Diego 2026: Prices and Financing, updated September 6, 2026 | Lars Remodeling industry — Accessed 2026-09-19
- Garage Conversion Cost in San Diego (2026 Guide) | Lumina Builders industry — Accessed 2026-09-19
- HUD FY 2027 Small Area Fair Market Rent Schedule, San Diego-Chula Vista-Carlsbad MSA ZIP codes (effective October 1, 2026) Government Data — Accessed 2026-09-20
- County of San Diego ADU Handbook (April 2024) Planning Department — Accessed 2026-09-20
Frequently Asked Questions
What are the ADU rules in unincorporated San Diego County?
In unincorporated San Diego County, ADUs are regulated by the County (not a city) and follow California state ADU law. A detached ADU can be up to 1,200 sq ft regardless of the main home's size, attached ADUs up to 50% of the main home's floor area, capped at 1,200 sq ft; the 50% limit does not apply to an attached ADU of up to 850 sq ft, or up to 1,000 sq ft with more than one bedroom. Rear setbacks are 4 ft minimum for any newly built detached or attached ADU, and qualifying ADU applications are approved administratively, with no public hearing.
How much does an ADU permit cost in San Diego County?
In unincorporated San Diego County, building and plan-check fees scale with the size and valuation of the ADU, so there is no single flat fee — request the current fee schedule from the County. None for an ADU with 750 sq ft of interior livable space or less (Gov. Code 66311.5); above that, fees are charged in proportion to the main home. The county park (PLDO) impact fee for an ADU is $4,400-$6,620 by local park planning area in 2026 (Spring Valley $5,431, Lakeside $4,916, Fallbrook $5,017, Ramona $4,875, Alpine $4,896), collected at permit issuance; traffic (TIF) and drainage fees depend on the parcel (DPW estimator). School fees: an ADU under 500 sq ft adds no assessable space (66311.5(c)(3)). Pre-2020 unpermitted units legalized under AB 2533 pay no impact or connection fees (Sec. 6156.x.A.25).. Total construction typically runs $250,000-$450,000; a garage conversion is cheaper at $80,000-$200,000.
Do I need owner-occupancy for an ADU in San Diego County?
Not required for ADUs (Sec. 6156.x has no requirement; AB 976 made the state ban permanent). JADUs: the county deed restriction and PDS-611 still require the owner to live in the house or the JADU (6156.x.B.3.a.iii), but Gov. Code 66333(b) as amended by AB 1154 (effective January 1, 2026) drops that where the JADU has its own bathroom, and the PDS Director's Determination of January 29, 2025 says state law prevails - raise it at the Zoning Counter..
Is my property in unincorporated San Diego County or inside a city?
This matters a lot: if your parcel is inside an incorporated city (San Diego, Chula Vista, Oceanside, Escondido, Carlsbad, El Cajon), that city's ADU code applies instead of the County's. Only unincorporated parcels follow the County rules on this page. Confirm your jurisdiction with the County before designing.
How many ADUs can I build in unincorporated San Diego County?
Single-family lot: one new detached ADU, plus one conversion ADU inside the house or an accessory structure, plus one JADU (Sec. 6156.x.B.1); the same allowance applies to a lot with several detached houses (A.22). Multifamily lot: conversions of non-livable space up to 25% of the existing units, plus detached ADUs - up to 8 on an existing complex (never more than the existing unit count) or 2 with a proposed complex (B.1.c-e, SB 1211). Guest living quarters cannot coexist with an ADU (6156.k).
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