Garage conversion · checked Oct 18, 2026
Garage conversion ADU fees in Hayward: $5,286–$5,684 for a 400 sq ft garage
That’s $5,825 less than building the same 400 sq ft as a new detached ADU in Hayward. Both sizes are under 750 sq ft, so there are no impact fees either way.
What changes
Why a conversion costs less in Hayward
- Sewer connection fee (ADU, where applicable): $5,825 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 | ||||
| Zoning conformance permit (ADU) | $498 | $498 | $498 | $498 |
| Building permit & plan check | ||||
| Building inspection fee (valuation table) | Est.$1,300 | Est.$1,300 | Est.$1,590 | Est.$1,590 |
| Building plan check (100% of inspection fee) | $1,300 | $1,300 | $1,590 | $1,590 |
| Planning review (35% of inspection fee) | $455 | $455 | $556 | $556 |
| Fire review (35% of inspection fee) | $455 | $455 | $556 | $556 |
| Technology fee (9% of inspection fee) | $117 | $117 | $143 | $143 |
| Policy planning fee (16% of inspection fee) | $208 | $208 | $254 | $254 |
| Permit issuance fee (35% of inspection fee) | $455 | $455 | $556 | $556 |
| Housing review fee (ADU) | $158 | $158 | $158 | $158 |
| Fire inspection fee | May apply$398 | May apply$398 | May apply$398 | May apply$398 |
| Address assignment | $340 | $340 | $340 | $340 |
| Impact fees | ||||
| Park impact fee (ADU 750+ sq ft) | Exempt | Exempt | Exempt | Exempt |
| School district fee | ||||
| School fee (Hayward Unified; statewide cap shown) | Exempt | Exempt | Up to$2,959 | Up to$2,959 |
| Utility connections | ||||
| Sewer connection fee (ADU, where applicable) | Exempt | May apply$5,825 | Exempt | May apply$5,825 |
| Modeled total | $5,286–$5,684 | $5,286–$11,509 | $6,243–$9,600 | $6,243–$15,425 |
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 Hayward
How much are the fees to convert a garage into an ADU in Hayward?
Our model of Hayward’s official fee schedules comes to $5,286–$5,684 for a 400 sq ft garage conversion and $6,243–$9,600 at 550 sq ft, with a 2,000 sq ft main home. A new detached ADU of the same size would be $5,286–$11,509 and $6,243–$15,425.
Is a garage conversion cheaper than a new ADU in Hayward?
In fees, yes: $5,825 less at 400 sq ft and $5,825 less at 550 sq ft. Sewer connection fee (ADU, where applicable) 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
- We assume type VB (wood-frame) construction for the valuation; type VA's minimum is $211.39/sq ft, and Hayward uses your stated valuation if it's higher.
- State SMIP and building standards fees, solid waste review and landscape inspection aren't included.
- School district rate not captured; shown at the statewide cap.
- Local size, height and parking rules not captured yet; the state minimums apply.
More
Keep going
Sources
Official sources
Every figure comes from these documents; each line’s quoted text is on the Hayward page.
- City of HaywardAdopted Master Fee Schedule, Fiscal Year 2026-2027 (effective July 1, 2026) (opens in new tab)
- City of HaywardThe Accessory Dwelling Unit (ADU) Process (handout) (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)