Garage conversion · checked Oct 18, 2026
Garage conversion ADU fees in Santa Clara: $3,646–$4,140 for a 400 sq ft garage
That’s $747 less than building the same 400 sq ft as a new detached ADU in Santa Clara. Both sizes are under 750 sq ft, so there are no impact fees either way.
What changes
Why a conversion costs less in Santa Clara
- Wastewater treatment plant capacity fee (per ADU): $747 for a new detached unit at 550 sq ft, $0 for a conversion. State law bars a new utility connection fee or capacity charge for an ADU inside an existing structure (Gov. Code §66311.5(d)).
Line by line: converted garage vs new detached ADU
2,000 sq ft main home (example assumption), law in force today. Garage sizes are examples: 400 sq ft is a typical two-car garage; 550 sq ft adds the 150 sq ft expansion.
| Fee | Garage, 400 sq ft | New detached, 400 sq ft | Garage + 150, 550 sq ft | New detached, 550 sq ft |
|---|---|---|---|---|
| Planning & zoning | ||||
| Architectural review: ADU / JADU (Planning) | $306 | $306 | $306 | $306 |
| General Plan / Advanced Planning surcharge | $326 | $326 | $393 | $393 |
| Building permit & plan check | ||||
| Building plan review (scaled by size) | $1,318 | $1,318 | $1,610 | $1,610 |
| Building permit (scaled by size) | $1,311 | $1,311 | $1,560 | $1,560 |
| Permit issuance fee | $101 | $101 | $101 | $101 |
| Electrical permit (residential, per sq ft) | $96 | $96 | $132 | $132 |
| Mechanical permit (new residential, per sq ft) | $40 | $40 | $55 | $55 |
| Plumbing permit (new residential, per sq ft) | $40 | $40 | $55 | $55 |
| Technology fee | $108 | $108 | $129 | $129 |
| Public works & encroachment | ||||
| Cost Analysis for Development, minor (Public Works) | May apply$494 | May apply$494 | May apply$494 | May apply$494 |
| School district fee | ||||
| School fee (district; statewide cap shown) | Exempt | Exempt | Up to$2,959 | Up to$2,959 |
| Utility connections | ||||
| Sanitary sewer conveyance fee (ADU 750 sq ft and larger) | n/a | n/a | n/a | n/a |
| Wastewater treatment plant capacity fee (per ADU) | Exempt | $747 | Exempt | $747 |
| Modeled total | $3,646–$4,140 | $4,393–$4,887 | $4,342–$7,794 | $5,088–$8,542 |
State law
What California guarantees for a garage conversion
A city must approve one ADU inside an existing accessory structure such as a garage, can’t require a setback for it, and can’t make you replace the parking you lose.
Gov. Code §66323(a)(1)
One accessory dwelling unit and one junior accessory dwelling unit per lot with a proposed or existing single-family dwelling if all of the following apply:
Gov. Code §66323(a)(1)(A)
may include an expansion of not more than 150 square feet beyond the same physical dimensions as the existing accessory structure
Gov. Code §66314(d)(7)
No setback shall be required for an existing living area or accessory structure or a structure constructed in the same location and to the same dimensions as an existing structure that is converted to an accessory dwelling unit or to a portion of an accessory dwelling unit
Gov. Code §66314(d)(11)
When a garage, carport, covered parking structure, or uncovered parking space is demolished in conjunction with the construction of an accessory dwelling unit or converted to an accessory dwelling unit, the local agency shall not require that those offstreet parking spaces be replaced.
Quoted from Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab), checked Oct 18, 2026.
FAQ
Questions about garage conversion in Santa Clara
How much are the fees to convert a garage into an ADU in Santa Clara?
Our model of Santa Clara’s official fee schedules comes to $3,646–$4,140 for a 400 sq ft garage conversion and $4,342–$7,794 at 550 sq ft, with a 2,000 sq ft main home. A new detached ADU of the same size would be $4,393–$4,887 and $5,088–$8,542.
Is a garage conversion cheaper than a new ADU in Santa Clara?
In fees, yes: $747 less at 400 sq ft and $747 less at 550 sq ft. Wastewater treatment plant capacity fee (per ADU) is lower for a conversion.
Do I have to replace the garage parking?
No. When a garage is converted to an ADU, state law bars the city from requiring replacement off-street parking (Gov. Code §66314(d)(11)).
Does a garage conversion pay impact or school fees?
No impact fees: the unit is under 750 sq ft. School fees apply only above 500 sq ft; at 550 sq ft the statewide cap would be up to $2,959, and the district may charge less.
Not modeled yet
What these totals leave out
- The schedule doesn’t say whether park in-lieu or traffic impact fees apply to ADUs. State law makes any such fee $0 at 750 sq ft or less and proportional to the main home above.
- Building Conformance Fee (valuation × $0.00032), Silicon Valley Power service fees and the sanitary sewer outlet charge per lot aren’t included.
- Fees are rounded down to the nearest nickel under the July 7, 2026 amendment (Resolution 26-9584); we use the amounts printed in the schedule.
More
Keep going
Sources
Official sources
Every figure comes from these documents; each line’s quoted text is on the Santa Clara page.
- City of Santa ClaraFY 2026/27 Municipal Fee Schedule (adopted April 21, 2026; Building Division amended July 7, 2026) (opens in new tab)
- California State Allocation Board (Department of General Services, OPSC)State Allocation Board item: 2026 adjustment to the Level I developer fee (meeting of January 28, 2026) (opens in new tab)
- California Legislative Information (leginfo.legislature.ca.gov)Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab)
- HCD via data.ca.govHousing Element Annual Progress Report (APR) data, Table A2: ADU building permits by year (opens in new tab)