San Diego County · cost guide
ADU construction prices in San Diego County: 2026 ranges
An ADU construction in San Diego County costs $305–$510 per sq ft, with a typical mid-size ADU running $92k–$184k at the county average. Small projects start around $61k; large or high-end work can reach $459k or more.
As of 2026, San Diego County runs about 2% above the LA County baseline due to coastal-zone review, hillside lots in North County, and a tight trade-labor market.
Updated
ADU Construction Cost by Size — SD County Average
County-average ranges (1.02× LA County baseline). Individual cities vary — see the table below.
| Size | Type | Range | Low | High |
|---|---|---|---|---|
| Small | JADU / studio | 150–400 sq ft | $61k | $133k |
| Medium | 1-bed garage conversion | 400–600 sq ft | $92k | $184k |
| Large | Detached 2-bed | 800–1,200 sq ft | $255k | $459k |
ADU Construction Cost by City in San Diego County
Every city in San Diego County, sorted alphabetically. Totals reflect each city's local cost multiplier. Cities in color have full project-specific pages.
| City | Small | Medium | Large |
|---|---|---|---|
| Alpine | $58k–$126k | $88k–$175k | $243k–$437k |
| Borrego Springs | $53k–$115k | $79k–$159k | $220k–$396k |
| Campo | $52k–$112k | $78k–$155k | $215k–$387k |
| Carlsbad | $72k–$156k | $108k–$216k | $300k–$540k |
| Chula Vista | $57k–$124k | $86k–$171k | $238k–$428k |
| Coronado | $87k–$189k | $131k–$261k | $363k–$653k |
| Del Mar | $90k–$195k | $135k–$270k | $375k–$675k |
| El Cajon | $54k–$117k | $81k–$162k | $225k–$405k |
| Encinitas | $75k–$163k | $113k–$225k | $313k–$563k |
| Escondido | $56k–$121k | $84k–$168k | $233k–$419k |
| Fallbrook | $57k–$124k | $86k–$171k | $238k–$428k |
| Imperial Beach | $57k–$124k | $86k–$171k | $238k–$428k |
| Julian | $57k–$124k | $86k–$171k | $238k–$428k |
| La Jolla | $87k–$189k | $131k–$261k | $363k–$653k |
| La Mesa | $58k–$126k | $88k–$175k | $243k–$437k |
| Lemon Grove | $54k–$117k | $81k–$162k | $225k–$405k |
| Mission Valley | $60k–$130k | $90k–$180k | $250k–$450k |
| National City | $53k–$115k | $79k–$159k | $220k–$396k |
| Oceanside | $60k–$130k | $90k–$180k | $250k–$450k |
| Poway | $63k–$137k | $95k–$189k | $263k–$473k |
| Ramona | $55k–$120k | $83k–$166k | $230k–$414k |
| San Diego | $63k–$137k | $95k–$189k | $263k–$473k |
| San Marcos | $59k–$128k | $88k–$177k | $245k–$441k |
| Santee | $57k–$124k | $86k–$171k | $238k–$428k |
| Solana Beach | $81k–$176k | $122k–$243k | $338k–$608k |
| Valley Center | $57k–$124k | $86k–$171k | $238k–$428k |
| Vista | $57k–$124k | $86k–$171k | $238k–$428k |
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What Affects ADU Construction Cost in San Diego County?
- ADU type (JADU vs attached vs detached).
- Site prep and grading.
- Utility connections.
- CA Title 24 energy compliance.
- City ADU permit timeline.
- SD County market dynamics: coastal-zone review, hillside lots in North County, and a tight trade-labor market, which shifts ADU construction totals about 2% above the LA County baseline.
- City variation within SD County: coastal and hillside cities can run 15–30% above the county mid-point, while inland labor markets price 10–20% below.
ADU Construction Sub-Type Comparisons
Garage Conversion ADU vs Detached ADU
Garage conversions reuse the existing slab and shell; a detached new-build ADU costs more but unlocks larger floor plans and higher rent.
Junior ADU (JADU) vs Attached ADU
A JADU (≤500 sq ft, within the home) shares utilities; an attached ADU is a true second unit with its own entrance and meter.
How to Get the Best Price on a ADU Construction in San Diego County
- Get line-itemized bids from two or three builders on the same scope; SD County ADU construction pricing commonly varies 10–25% between contractors.
- Compare bids from contractors based in multiple SD County cities; inland-based crews servicing coastal jobs often beat coastal-based pricing.
- Bid in shoulder seasons (Jan–Mar or Sep–Oct) when SD County contractor schedules are open and rush premiums disappear.
- Verify CSLB license, insurance, and bond before paying any deposit. California caps deposits at $1,000 or 10% of contract, whichever is less.
What is an ADU construction?
An accessory dwelling unit (ADU) is a second, self-contained home on a single-family lot, with its own kitchen, bathroom and entrance. It can be detached, attached to the main house, a converted garage, or a junior ADU of up to 500 sq ft inside the existing home.
How to get an accurate price
- 1.Write down the scope: size, any layout changes, the finish level, and who supplies fixtures and materials.
- 2.Get bids from two or three licensed builders who work in San Diego County, all pricing that same ADU construction scope.
- 3.Line the bids up item by item. Check allowances, permits, exclusions, and whether overhead and profit are shown.
- 4.Before any deposit, check each builder's CSLB license and insurance. As of 2026, California caps a home improvement down payment at $1,000 or 10% of the contract, whichever is less, according to the Contractors State License Board.
Already have a bid? Grade it in two minutes or read how to compare quotes.
Questions about ADU Construction in San Diego County
How much does an ADU construction cost in San Diego County?
An ADU construction in San Diego County costs $61k–$459k, with a typical mid-size ADU running $92k–$184k at the county average.
Where is ADU construction cheapest in SD County?
Within San Diego County, inland and value-tier cities price ADU construction jobs 10–25% below the county average, while coastal and luxury-tier cities can run 20–35% above. See the city-by-city table below for exact totals.
Do I need a permit for an ADU construction in San Diego County?
Yes for most scopes — the city building department (San Diego DSD, Chula Vista, Oceanside, etc.) or County of San Diego Planning & Development Services for unincorporated parcels requires permits any time you move plumbing, gas, electrical, or change structure. Like-for-like cosmetic refreshes generally don't.
Keep exploring
Compare ADU construction costs across San Diego County, or browse other projects and guides.
More SD County cost guides
ADU Construction by city
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