SAN DIEGO ADU COST
How much does an ADU cost in San Diego?
It depends on what you build and what your property needs. Here are three sets of numbers: what a San Diego builder charges, what owners declared on City permits, and what the City charges in fees.
THE SHORT ANSWER
One builder’s all-in price: $300,000 for 500 sq ft.
One San Diego builder publishes a typical all-in price of $300,000 for a 500 sq ft one-bedroom ADU and $350,000 for a 750 sq ft two-bedroom. On City permits, conversions declared a median $84,000 of construction work and new ADUs $185,000. City permit fees for a small ADU start at about $6,490.
Check my propertyWHAT BUILDERS CHARGE
A new detached ADU.
| ADU | Construction | All-in | All-in per sq ft |
|---|---|---|---|
| 500 sq ft, one bedroom | $220,000 | $300,000 | $600 |
| 750 sq ft, two bedrooms | $275,000 | $350,000 | $470 |
Published prices from a San Diego design-build firm, updated March 2026. All-in includes design, permits, site work, utilities, and construction with standard finishes and appliances. Your design and your property will change the price.
WHAT CITY PERMITS SHOW
What owners declared.
- Conversions
- $84,000 The median of 1,993 permits to convert a garage or other existing space. The middle half ran from $59,000 to $150,000.
- New ADUs
- $185,000 The median of 3,106 permits for new detached and attached ADUs. The middle half ran from $116,000 to $266,000.
The construction value declared on City of San Diego ADU permits, January 2024 to September 18, 2026. It is the value of the construction work only. It does not include design, fees, or the rest of the project. See the permit data by neighborhood.
WHAT THE CITY CHARGES
Permit fees.
| Fee | Detached up to 500 sq ft, or attached ADU or JADU up to 1,100 sq ft | Detached over 500 sq ft |
|---|---|---|
| Plan check | $3,512.92 | $8,085.26 |
| Inspection | $2,228.29 | $8,401.90 |
| General Plan maintenance | $737.00 | $737.00 |
| Mapping | $12.16 | $12.16 |
| Fees shown so far | $6,490.37 | $17,236.32 |
- An attached ADU or JADU over 500 sq ft adds a plan check and inspection charge for each square foot over 500.
- San Diego Unified charges a school fee of $5.38 per square foot when the new living space is more than 500 sq ft. For a 749 sq ft ADU, that is $4,029.62. Other school districts set their own rates.
- ADUs under 750 sq ft and all JADUs do not pay the City's development impact fees. ADUs of 750 sq ft or more may pay them.
- Water and sewer capacity fees can apply when the project adds a new water meter. Additional fees may apply.
For example, a 749 sq ft detached ADU in San Diego Unified comes to $21,265.94 in the fees shown here. City fees from Information Bulletin 501, August 2026.
THE ALL-IN BUDGET
Six parts of the total.
Path, size, layout, and finish level
Design, drafting, and triggered studies
Reviews, permits, and agency charges
Access, drainage, sewer, water, and power
Structure, systems, fixtures, and appliances
Coordination, financing, and contingency
ONE NUMBER
Construction quote
May cover only the work in the builder’s scope.
WHAT IT LEAVES OUT
Additional costs
Plans, fees, site work, utilities, financing, and a reserve, wherever the quote leaves them out.
THE FULL DECISION
Total project budget
Use the full budget when comparing options.
Check what the quote already includes before adding plans, fees, utilities, or other costs.
COMMON QUESTIONS
What homeowners ask next.
How much does a garage conversion cost in San Diego?
On City permits, conversions of a garage or other existing space declared a median $84,000 of construction work. That is construction only. Add design, fees, and any utility work to get the project total.
Is cost per square foot useful?
Only as a rough comparison. In the builder prices above, a 500 sq ft ADU costs $600 per square foot all-in and a 750 sq ft ADU $470, because some costs stay the same at any size.
Are permit fees the same for every ADU?
No. Plan check and inspection fees depend on the type and size of the ADU. School fees and impact fees depend on the size and the school district.
Should I include financing in the project budget?
Yes, if borrowing is part of the plan. Keep financing costs separate from design and construction so the decision remains clear.
How large should the contingency be?
That depends on design certainty, site conditions, existing structure, contract scope, and unresolved risks. Name the risks before setting the reserve.
YOUR PROPERTY IS THE NEXT QUESTION
Check your property for free.
Enter your address for a free Untapped Value Report. No account or phone number needed.
Check my property