What an ADU really costs in San Diego (2026 permit data)

ADU cost by build type in San Diego (2026 permits)

The citywide median hides a wide spread. We sorted all 750 single-ADU building permits the City of San Diego issued from January 1 to October 15, 2026 by what the permit description says is being built. The cheapest common route, converting a garage, had a median declared value of $81,800. A new two-story detached ADU had a median of $198,600, more than double. That gap matters more than anything else when you set a budget, so start by deciding which kind of ADU your lot can take.

*Days from application to permit issue across all review tracks, so these differ from the standard-track figure in our permit timeline. Build types are sorted from words in each permit description. Download this table (CSV).

What each build type means for your budget

Garage conversion (226 permits, median $81,800). This is the most common ADU in San Diego and the least expensive. The slab, walls and roof already exist, so most of the money goes to insulation, windows, a kitchen, a bathroom, and bringing plumbing and electrical up to code. The middle half of permits ran $55,700 to $130,100. Costs climb when the slab needs work for new plumbing lines, when the garage sits too close to a property line for windows, or when the roof framing can't carry new loads.

Other conversions (79 permits, median $101,000). Converting a room, a basement, a workshop or another accessory building came in higher than a garage. These spaces often need more layout changes, new exits, or a separate entrance.

Prefab or manufactured detached ADUs (15 permits, median $59,800). Permits that name a prefab, modular or manufactured unit declared the lowest value of any new-build route. Read this one carefully: the sample is small, and declared value for a factory-built unit may not include the factory price, delivery, crane, foundation and site work in the same way a site-built job does. Ask any prefab seller for a full installed price.

Attached additions (92 permits, median $115,300). Building onto the main house shares a wall and sometimes utilities. The median sits close to the citywide figure, but the top quarter starts at $235,000, the widest high end of any type, because some attached jobs also remodel the main house on the same permit.

New one-story detached ADUs (151 permits, median $125,900). A backyard cottage needs a new foundation, framing, roof, and its own utility runs. That makes it the baseline for new construction. The middle half ran $87,700 to $195,200.

ADUs above a garage (58 permits, median $162,100). A second-story unit over a new or existing garage needs structural engineering, stairs and often a new foundation for the garage. These permits also took the longest to issue, with a median of 334 days.

New two-story detached ADUs (89 permits, median $198,600). The most expensive standalone option. Two stories mean more framing, stairs, and engineering, but also more living space on a small footprint. Note how tight the range is: the middle half ran $153,400 to $208,900.

ADUs built along with a new main house (18 permits, median $197,600). When a lot is cleared and rebuilt, the ADU is often permitted with the new home. These are a separate category of project, so we kept them out of the comparisons above.

Junior ADUs (83 permits, median $67,800). A JADU is a unit of up to 500 sq ft created inside the existing home, usually from a bedroom, with an efficiency kitchen. Permits that added only a JADU and no full ADU had a median value of $67,800 and issued fastest, at a median of 157 days. If you mainly want rental income or space for family and have a spare room, price a JADU first.

ADU cost by San Diego neighborhood

Neighborhood medians move a lot, and the main driver is usually the mix of projects, not land or labor prices. Areas where many owners convert garages show lower medians; areas where most permits are new detached or two-story units show higher ones. College Area had the highest median ($195,200) and North Park the lowest ($79,500). College Area had the most single-ADU permits of the neighborhoods we track (73). Click a neighborhood for its own page with local detail.

Permits are matched to the nearest neighborhood center within about 1.6 miles. Download (CSV).

Does a fire zone change ADU cost?

166 of the 2026 single-ADU permits mention a Very High Fire Hazard Severity Zone (VHFSZ) in their description. Their median declared value was $125,200, compared with $118,200 for permits that don't mention one. That is a modest difference, smaller than the gap between build types. Fire-zone rules (ignition-resistant siding, ember-resistant vents, tempered glass and similar requirements under the California building code's wildland-urban interface chapter) add cost to materials, but the permits in these areas also skew toward particular neighborhoods and project types. In this data the fire-zone permits issued faster, at a median of 192 days versus 278 for the rest; we don't know why, so don't plan around it. Check your parcel's fire zone on the City or CAL FIRE map before you design.

How many ADUs San Diego is permitting in 2026

The City issued 713 single-ADU building permits from January through September 2026, an average of about 79 a month. The busiest month was Mar (98) and the slowest was Aug (66). Steady volume means local builders and designers stay busy, so it pays to line up quotes early, especially if you want to start construction in spring.

ADU budget estimator (from real permits)

Pick a build type and, if you like, a neighborhood. The estimator shows the middle half and median of what similar 2026 permits declared. It does not guess at your design. Use the checklist under it to see what you still need to price separately.

How to budget an ADU in San Diego, step by step

1. Confirm what your lot allows. Check zoning, setbacks, fire zone, slope, and where the sewer line runs. The City's ADU guide, Information Bulletin 400, covers the rules.
2. Pick a build type. Use the table above. If you have a garage you don't need, a conversion usually costs the least. If you want the most space, compare two-story detached with above-garage.
3. Set a construction range from real permits. Use the low, median and high columns for your type. Plan near the median unless your site is simple.
4. Add the soft costs. Design, engineering, energy reports, surveys and fees sit on top of construction. Ask each designer to list them line by line.
5. Price utilities early. A new sewer lateral, water meter, or electrical panel upgrade often follows an ADU permit. Our what comes next page shows how soon those permits usually follow.
6. Get at least three comparable quotes. Give every builder the same plans and scope, then compare with our fair quote checklist and the quote checker below.
7. Plan for time. Permits took months in 2026. Carrying costs, rent you aren't collecting yet, and loan interest during that wait belong in the budget too.

Ways San Diego homeowners pay for an ADU

Most owners combine savings with one of a few common loan types. Each has trade-offs, so talk to a lender before you sign a build contract.

• Home equity line of credit (HELOC): draw money as the build progresses and pay interest only on what you use. Rates usually float.
• Cash-out refinance: replaces your current mortgage with a larger one. Worth comparing carefully if your current rate is low.
• Construction or renovation loan: some lenders lend against the property's value after the ADU is built, which can help owners without much equity yet.
• Builder or prefab financing: some companies offer their own programs. Read the terms closely and compare them with a bank offer.

We don't arrange loans and aren't paid by lenders. This is general information, not financial advice.

More ADU cost questions

How we calculated these numbers

We used the City of San Diego's public development permit data and kept building and combination building permits issued from January 1 to October 15, 2026 that were not cancelled and that add exactly one ADU (750 permits), plus permits that add only a JADU. Build types come from the permit description: "conversion" with "garage", other conversions, prefab or manufactured, above a garage, detached one-story or two-story, attached additions, and permits that also build a new main house. Values are the construction valuation the applicant declared, rounded to the nearest $100. "Days to issue" counts from application to issue. Full notes are on our methodology page.

Last updated October 16, 2026.

How much does an ADU cost in San Diego?

In 2026 City of San Diego building permits for a single ADU, the median declared construction value was $120,900 (middle half $76,000–$197,700, 750 permits). Garage and other conversions ran lower (median $89,600); new detached ADUs ran higher (median $154,300). Declared value excludes design, City fees, utility work and often finishes, so real budgets run higher.

How long does an ADU permit take in San Diego?

For 2026 ADU building permits on the standard track, the median was 293 days from application to issue; a quarter took 170 days or less and a quarter took 486 days or more. Most of that time is usually correction rounds between the City and your designer.

Are ADUs exempt from impact fees in San Diego?

The City says ADUs under 750 sq ft, and the first two ADUs on a property, are exempt from Development Impact Fees (SDMC §142.0640). School fees, the General Plan Maintenance Fee, plan check and permit fees, and possibly water/sewer capacity fees still apply.

What usually comes after an ADU permit?

On the same parcels in 2026 City permits, the median gap to a sewer or utility permit was about 38 days, an electrical panel upgrade about 68 days, a fence about 112 days, and solar about 115 days.

Are you an ADU builder?

No. This is a free guide and quote-matching service. With your consent we pass your request to up to 3 local licensed builders. You never have to hire anyone.