1000 sq ft ADU cost in San Diego: price, fees and floor plans

1000 sq ft ADU cost in San Diego

Snap ADU's published San Diego prices (March 2026) put a detached 1,000 sq ft ADU at about $425,000, or about $425 per square foot. That base price includes design, permit management, about $35,000 of site work on a level lot and standard finishes. It leaves out city fees, demolition, retaining walls and a separate electric meter.

A second builder's range gives you a cross-check. Lars Remodel's October 2026 cost guide puts a detached ADU in San Diego at $250,000 to $450,000 or more, and an attached ADU at $200,000 to $350,000 or more. A 1,000 sq ft unit sits near the top of the detached range.

Site extras come from Snap ADU's guide to site-work costs. Treat all of these as one builder's published numbers, not quotes. A flat lot with short utility runs lands near the base price; a sloped lot with a new meter can add $20,000 to $35,000, and more with retaining walls. Run your own numbers in our ADU cost calculator, and see what an ADU costs in San Diego for every size and type.

Why 1,000 sq ft costs less per foot

Per square foot, a bigger ADU is cheaper. The same price list puts a 500 sq ft unit at about $300,000, or $600 per sq ft. Doubling the size adds about $125,000, not another $300,000, because design, permits, utility trenching and the kitchen and bathroom count are mostly fixed costs. The second bathroom and extra bedroom are what you pay for.

1000 sq ft ADU floor plans

At 1,000 sq ft you can fit two bedrooms and two full baths with a real living room, or squeeze in a third bedroom. The free plan sets that local governments publish show the range:

Plans come from the County of San Diego's plan listing and Escondido's pre-approved ADU program. Notice the County's Plan D spends its 1,000 sq ft on one large bedroom and a half bath. That's a good layout for an owner downsizing into the backyard; the Escondido plan is the better rental layout.

Free 1000 sq ft ADU plans in San Diego

The County's plans are free to download, but they're about 85% complete: you or a designer still add the site plan, stormwater documents, energy calculations and truss design. The City of San Diego accepts the County's plans, along with Chula Vista's and Encinitas's, for a 30-day review. Our guides to ADU floor plans by size and pre-approved ADU plans in San Diego cover each program.

One story or two

A single-story 1,000 sq ft unit takes a big piece of a typical backyard. If your yard can't spare it, San Diego's code allows an ADU of up to two stories in single-family zones, which halves the footprint. Stairs, a second floor system and taller walls add cost; see our two-story ADU guide.

Fees on a 1,000 sq ft ADU

Fees climb with size, but not evenly. In Snap ADU's February 2026 table of City of San Diego fees, a 999 sq ft ADU comes to about $26,430. That's only about $1,300 more than a 749 sq ft unit, while the jump from 499 to 749 sq ft is about $14,400. These are a builder's estimates, not an official city fee schedule.

Impact fees above 750 sq ft

Statewide, an ADU of 750 sq ft or less owes no impact fees. Above that, a city can charge them, but only in proportion to the size of the main house. A 1,000 sq ft ADU is over the line, so outside the City of San Diego expect some impact fees.

Two things soften that:

• San Diego's exemption. The City of San Diego's municipal code exempts the first two ADUs on a property from development impact fees, whatever their size. A 1,000 sq ft ADU there pays no development impact fee.
• SB 1117 from 2027. Starting January 1, 2027, SB 1117 limits impact fees on an ADU over 750 sq ft to the area above 750. On a 1,000 sq ft unit, that's 250 sq ft instead of 1,000. See California ADU laws for 2027.

School fees

School fees still apply at this size; only units under 500 sq ft skip them. San Diego Unified charges $5.38 per square foot, which works out to about $5,380 on a 1,000 sq ft unit. Other districts set their own rates.

Can you build a 1,000 sq ft ADU?

In most of California, yes. 1,000 sq ft is a number the state wrote into law. Government Code section 66321 says a city can't set its maximum ADU size below 850 sq ft, or below 1,000 sq ft for an ADU with more than one bedroom. So every city has to let you build a two-bedroom ADU of at least 1,000 sq ft, subject to its other standards.

The 800 sq ft figure is the no-questions-asked guarantee. Above it, a 1,000 sq ft unit has to meet your city's local rules for setbacks, lot coverage and floor area. In the City of San Diego, the municipal code allows new ADUs up to 1,200 sq ft, so 1,000 is comfortably inside the limit. Since 2026, state size limits are measured as interior livable space, so ask your designer how a plan's square footage is counted before comparing it to a cap. The full rulebook is in our guide to California ADU laws.

1,000 sq ft vs. a smaller ADU

Prices from Snap ADU; fees from its fee table; per-foot figures are our division. The table points to a few practical choices:

• If you're choosing between 750 and 1,000, the fee difference is small, so the decision is mostly about $75,000 of construction against a second bedroom or bath.
• If you're choosing between 1,000 and 1,200, the extra 200 sq ft costs about $25,000 more to build in this price list, plus about $4,700 in fees. See our 1200 square foot ADU guide.
• If you want the lowest total, stay at 800 sq ft or less to keep the state's setback guarantee, or under 500 to drop school fees.

Renting out a 1,000 sq ft ADU

A two-bedroom, two-bath unit opens up a wider rental market than a studio: roommates, a small family, or a parent with a caregiver. In the City of San Diego, ADU rentals must run at least 31 days, so plan on long-term tenants rather than vacation guests. Rents move too fast for a fixed number here; our guide to ADU rental income in San Diego shows how to price a unit and weigh it against the build cost. When you're ready, compare verified ADU builders in San Diego or start from our list of the best ADU builders in San Diego.

Common questions