Fees are a part of ADU cost that surprises people. State law limits them. This guide explains the main limits and what to ask locally.
LA ADU Guide is an information site, not a law firm or a builder. Read the statute or ask your agency before relying on this page.
A recent renumbering
SB 543, effective January 1, 2026, amended and renumbered the fee rules. They used to sit in Gov. Code 66324 and are now in Gov. Code 66311.5, according to a law firm summary. Older city handouts may still cite the old number. HCD has flagged incorrect citations in local ordinances too. If you see an old number, search by the topic and check the current section.
Three kinds of charges
They are easy to mix up.
- Impact fees. One-time charges that fund things like parks, traffic and public facilities. They are set under the Mitigation Fee Act (Gov. Code 66000 and following).
- Utility connection fees and capacity charges. Charges from water, sewer or other utilities for connecting to the system.
- Permit and plan check fees. The city's cost to review plans and inspect work. These are not impact fees. See our permit process guide.
The statute treats the first two differently. Under 66311.5(c)(2), "impact fee" does not include "any connection fee or capacity charge."
The 750 square foot rule
Under Gov. Code 66311.5(c)(1):
- No impact fee may be imposed on an ADU of 750 square feet or less of interior livable space.
- No impact fee may be imposed on a junior ADU (JADU) of 500 square feet or less.
- For a larger ADU, the fee "shall be charged proportionately in relation to the square footage of the primary dwelling unit."
Example of the idea, not a quote: if the ADU is half the size of the main home, a proportional fee would be half of what a new home of that size would pay. Ask the agency for its worksheet.
Some sources describe the over-750 rule as charging only the area above 750 square feet. We could not confirm that wording in the statute text we read, so ask the agency which method it uses.
Fee rules by case
| Case | Impact fee | Source |
|---|---|---|
| ADU of 750 sq ft or less | None | Gov. Code 66311.5(c)(1) |
| JADU of 500 sq ft or less | None | Section 66311.5(c)(1) |
| Larger ADU | Proportionate to the square footage of the primary dwelling | Section 66311.5(c)(1) |
| Conversion or small unit under 66323(a)(1) | No new utility connection or related fee required | Section 66311.5(d) |
| New detached unit | Utility may charge a connection fee, not above reasonable cost | Section 66311.5(e) |
School fees
School district fees are a separate rule. Under 66311.5(c)(3), a unit under 500 square feet counts as construction that does not increase assessable space by 500 square feet for the school fee statute (Education Code 17620). Check with your school district.
Utility connections
Two cases matter.
Conversions and small units (units described in Gov. Code 66323(a)(1)). This covers, for example, converting existing space inside a home or accessory structure. Under 66311.5(d), the utility cannot require a new or separate connection directly to the unit or charge a related connection fee or capacity charge. There are exceptions if the ADU is built with a new single-family home, or if it is sold separately under Gov. Code 66342.
New detached or other units. Under 66311.5(e), the utility may require a separate connection and charge a fee. The charge must be proportionate to the unit's burden, based on square footage or drainage fixture unit (DFU) values. It "shall not exceed the reasonable cost of providing this service."
Also, under 66311.5(b), a utility may not treat an ADU or JADU as a new residential use for connection fees or capacity charges, unless it was built with a new single-family home.
In plain terms: a garage conversion should not trigger a new sewer or water connection fee, and a new detached ADU may.
Who charges what in Los Angeles
- City of Los Angeles. Building permits come from LADBS. Water and power come from the Department of Water and Power. Sewer charges come from the city's sanitation bureau.
- Unincorporated LA County. Fees come from county departments and special districts.
- Other cities. Each city sets its own fee schedule, and water may come from a separate district.
Ask each office for a written fee estimate for your lot and unit size. Ask which charges are impact fees and which are connection fees. Under the law, they follow different rules.
Steps to take
- Measure the interior livable space of the planned ADU.
- Ask the building department for its ADU fee schedule.
- Ask whether the unit is under 750 square feet and therefore exempt from impact fees.
- Ask your water and sewer providers whether a new connection or meter is required.
- Get the answers in writing.
- Add the totals to your budget. See ADU cost in Los Angeles.
If a fee looks wrong
- Ask the agency to cite the code section it uses for the fee.
- Compare it to Gov. Code 66311.5.
- Ask for the fee basis, such as square footage or fixture counts.
- Contact the HCD ADU team through its ADU page if you think a local rule conflicts with state law.
Quick checklist
- [ ] Unit size in interior livable square feet
- [ ] Conversion or new construction
- [ ] Impact fee estimate, in writing
- [ ] Water and sewer connection requirements
- [ ] School district fee, if any
- [ ] Permit and plan check fees
State rules change often. The last major reform noted here came with SB 543, effective January 1, 2026. See the ADU costs hub and ADU rules in California.