ADU Costs in San Diego, California

Planning-level pricing guide by ADUWizard.com
Updated for 2026 budgeting

Most California cities did the minimum on ADUs and called it a day. San Diego did the opposite. It took the state baseline and built an aggressive incentive on top of it, and that one decision changes the whole conversation here. In most cities I help people plan one ADU. In San Diego, on the right lot, we are sometimes planning three or four.

I have watched that program turn an ordinary single-family lot into a small income property, and I have also watched people assume they qualify when they do not. So let me give you the honest version: what it actually costs to build here in 2026, how the Bonus Program math works, and why the same unit can swing six figures between the coast and the inland neighborhoods.

Quick disclaimer: This is a budgeting guide, not a quote or legal advice. San Diego bids move hard with coastal labor, slope, soils, and utility routing. Use these ranges to compare bids apples to apples, not as a fixed price.

The San Diego ADU Bonus Program (Why This City Is Different)

Here is the piece nobody explains in plain English. Under the San Diego ADU program, qualifying lots, usually inside transit priority areas, can build bonus ADUs beyond the state minimum. The trade is affordability: to unlock the bonus units, you deed-restrict some of them as affordable for a set period. On the right parcel, that has let owners put multiple units where the state would otherwise cap them.

I will tell you my honest read, because it matters for your timing. This is the most generous ADU density in the state, and generous density programs rarely stay untouched for long. If your lot qualifies and the numbers pencil, I would not sit on it for three years waiting to see what happens. Your designer will live inside the city’s permit bulletin 400, so get a feasibility read early.

For a standard single ADU, San Diego just follows California: no owner-occupancy, ministerial 60-day review once your application is complete, and detached units generally up to 1,200 sf.

San Diego ADU Cost in 2026 (by Type)

Type	Typical size	All-in cost	What usually drives it
Garage conversion	400–650 sf	$110k–$235k	slab moisture, panel upgrades, egress
Basement / interior	450–800 sf	$150k–$280k	headroom, moisture, plumbing reroutes
Attached ADU / addition	500–900 sf	$200k–$380k	structural tie-ins, roof and MEP
Detached new-build	500–1,200 sf	$260k–$500k	foundation, utilities, full envelope
Prefab / modular installed	500–900 sf	$220k–$440k	foundation, crane, hookups still apply

All-in cost per square foot runs roughly $260–$430 for conversions and $340–$560 for detached units.

San Diego ADU Cost by Size

Size	Conversion	Detached
400–500 sf (studio)	$110k–$220k	$260k–$380k
600–750 sf (1-bed)	$150k–$280k	$300k–$450k
900–1,200 sf (2-bed)	$200k–$300k	$360k–$500k

Coast vs Inland: The San Diego Detail That Moves Your Budget

This is the part most guides skip. San Diego is not one price. A detached ADU in a coastal neighborhood, La Jolla, Pacific Beach, Point Loma, prices very differently than the same unit in East County or the South Bay. Coastal jobs carry higher labor rates, tighter access, and sometimes coastal overlay review. Inland San Diego, El Cajon, La Mesa, parts of Chula Vista, tends to run 10 to 20 percent cheaper on the same scope.

If your budget is tight and your lot is flexible, that geography is a real lever. I have seen the exact same 750 sf plan come in $60k to $90k apart across town.

The San Diego Hidden Costs

Item	When it hits	Planning range
Slope / soils / retaining	canyon and hillside lots	$15k–$60k+
Utility trenching and upgrades	detached far from the house	$8k–$30k
Coastal overlay review	coastal-zone parcels	time plus consultant fees
Soft costs (design, plan check, fees)	every project	$15k–$45k
Panel / service upgrade	heat pumps, EV, older panels	$3k–$15k+

Example San Diego Budget: 700 sf Detached ADU

Category	Budget
Design + engineering	$16,000–$32,000
Permits + fees	$8,000–$22,000
Sitework + utilities	$25,000–$60,000
Foundation + framing + envelope	$95,000–$170,000
MEP (heat pump, plumbing, electrical)	$45,000–$80,000
Interior finishes	$40,000–$85,000
Contingency	$25,000–$50,000
Total all-in	$260,000–$500,000

San Diego ADU Permit Timeline

Phase	Typical duration
Feasibility + design	6–12 weeks
Plan review (standard)	4–8 weeks
Plan review (pre-approved plan)	1–3 weeks
Construction	16–30 weeks
Total, start to finish	8–14 months

The pre-approved standard plans are the quiet money-saver here. If a catalog plan fits your lot, you skip a big slice of design cost and cut review to a couple of weeks.

Where San Diego Ranks in California

By our own California cost data, San Diego sits in the pricier half of the state, but comfortably below the Bay Area. A detached San Diego ADU runs close to Long Beach, above value markets like Riverside and Fresno, and well under San Jose and San Francisco. Coastal labor is most of the reason it is not cheaper.

FAQs (San Diego)

How much does an ADU cost in San Diego in 2026?

Budget roughly $110k–$235k for a garage conversion and $260k–$500k for a detached ADU. Coastal neighborhoods run at the top of those ranges; inland East County and South Bay run 10 to 20 percent lower on the same scope.

What is the San Diego ADU Bonus Program, and do I qualify?

It lets qualifying lots, generally in transit priority areas, build extra ADUs beyond the state minimum in exchange for deed-restricting some units as affordable. Not every lot qualifies, so get a feasibility check against permit bulletin 400 before you design.

How fast can I get an ADU permit in San Diego?

Standard review is about 4 to 8 weeks. A pre-approved standard plan can drop that to 1 to 3 weeks. The state 60-day clock starts when the city deems your application complete.

Is it cheaper to convert a garage than build detached in San Diego?

Almost always. A garage conversion runs $110k–$235k versus $260k–$500k for a detached unit, as long as the existing slab, structure, and utility routes cooperate.

For the statewide picture, see our California ADU cost guide and compare Los Angeles. The Data Hub tracks these ranges as they move.