How much does an ADU cost in San Diego?
Written from Escondido
There is no honest single number.
A junior ADU carved out of a bedroom and a new two-story unit in the backyard are not the same job. This page is what changes the price, written by a design-build contractor in Escondido that prices the lot, not a national average.
BNC Builders. License #1050284. 101 State Pl Suite N, Escondido, CA 92029. Free in-home consult.
What search results hide
Why a page-2 average is useless.
Search for “adu cost san diego” and you get a range wide enough to hide the lot. This page used to do that too. The dollar bands are off until they are BNC's numbers from real bids, not market copy.
Type matters more than a citywide average
A garage conversion reuses a shell. A detached ADU adds foundation, roof, and a full utility run. Those are different jobs, not points on one countywide range.
City vs county vs Escondido is a different permit desk
Fees and review time move with the address. City of San Diego, the City of Escondido, and unincorporated county lots are not the same desk.
Utilities and slope show up after the pretty floor plan
Trenching, sewer, and a tight side yard are where bids jump. Site work is not a line you can guess from a stock layout.
Size is not a straight line
A 400 sq ft studio and a 1,200 sq ft two-bedroom do not scale by the square foot. Wet rooms, finish, and access change the number more than raw area.
Per-foot shortcuts
ADU price per square foot.
A per-foot number is a shortcut and lies when you mix types. A garage conversion looks cheap per foot because the walls exist. A new detached unit looks expensive because you pay for structure and wet rooms. Finish level swings the same square footage.
We give a per-square-foot range in the estimate, tied to type and finish. We do not publish a countywide dollars-per-square-foot figure.
The estimate line items
What you are paying for.
Names only. Share of budget changes with the lot, so we do not invent percents.
01
Design and engineering
Plans, structure, Title 24, and soil when the lot needs it.
02
Permits and city or county fees
The desk on the address sets the fee line. See San Diego ADU regulations for the permit path.
ADU regulations03
Site and utilities
Demo, grade, trench, and foundation.
04
The building
Frame, roof, electrical, plumbing, HVAC, insulation, and drywall.
05
Finish
Cabinets, counters, flooring, fixtures, and paint.
Four types, no fake bands
Cost by type, without published ranges.
BNC builds all four types on /adus and /adus/types. Relative order, cheapest to most: JADU, garage conversion, attached, detached. That order can flip if the garage is a mess or the yard is an easy pad.
Junior ADU (JADU)
Inside the existing house, under 500 sq ft. Fastest permit path. You are converting space you already heat and plumb.
Garage conversion
The shell is there. You still add a kitchen, bath, insulation, and a legal exit. You lose the parking.
Attached ADU
Shares a wall. Less yard lost. New roof line and a separate entrance.
Detached ADU
A new building. Highest cost, most privacy. Two-story only happens here.
Artisan ADU, Fallbrook — a finished unit on a real lot, not a stock floor plan.
The address sets the desk
City of San Diego vs Escondido vs the county.
City of San Diego Development Services reviews city lots. California law: cities act on a complete ADU application in 60 days. That clock is the city's, not a BNC promise of a finished building.
Escondido is its own city. BNC is based there. Unincorporated county lots use the county desk. We put the jurisdiction in the estimate. We do not quote a school-fee dollar on this page.
Full path, not a week count
How long an ADU actually takes.
The ADU page FAQ says the full path — design, permits, and build — runs 8 to 14 months. We manage plans, engineering, and city submissions. Financing help is listed as available.
The process already on the site is feasibility, then design and permits, then build. Free consult. One team. See the ADU construction process.
Work already on the site
A San Diego ADU, not a stock photo.
These are the ADU jobs already named on the live site. No extra projects, no invented photos.
“BNC turned our unused backyard space into a beautiful rental unit. The permit process seemed daunting, but they handled everything. Now we have monthly income covering our mortgage.”
Learn more about ADUs in San Diego.
Frequently asked questions
ADU cost questions, answered.
How much does an ADU cost in San Diego?
It depends on type, size, finish, and the lot. There is no honest single number, and we do not publish a countywide band. The estimate after we see the property is the number.
What is the cost per square foot?
It changes with type. A garage conversion and a new detached ADU should not share a per-square-foot figure. We give a per-square-foot range in the estimate, tied to type and finish.
How much does an ADU permit cost in San Diego?
Permit fees sit on top of construction. City of San Diego, Escondido, and county desks differ. The real fee line is in the estimate for that address.
Is a garage conversion cheaper than a new detached ADU?
Usually, because the shell exists. You still pay for wet rooms and legalization, and you lose the garage. A rough garage or an easy backyard pad can flip that order.
How much does a 2-story ADU cost?
A two-story ADU only happens as a detached unit. Extra framing and stairs. We price it after setbacks and height limits on the lot.
Can I get a free estimate?
Yes. Free in-home consult. Call (760) 658-6238. 101 State Pl Suite N, Escondido, CA 92029.
Get an ADU estimate
We visit, measure, and write the estimate. Design, permits, and build stay on one team. (760) 658-6238 · 101 State Pl Suite N, Escondido, CA 92029 · License #1050284