# ADU impact fees and the 750 square foot line

> A few square feet can decide whether an ADU owes impact fees at all. The line is drawn at 750, and it is measured in a specific way.

Source: https://www.lotlinepermits.com/california/laws/adu-impact-fees/
Publisher: Lotline
Last reviewed: 2026-11-10

## Key points

- No impact fee on an ADU with 750 sq ft of interior livable space or less. [1]
- Above that, the fee is proportionate to the size of the main house. [1]
- Connection fees and capacity charges are a separate category. [1]

## The rule

A local agency, special district or water corporation may not impose any impact fee on an ADU that has 750 square feet of interior livable space or less. The same protection covers a junior ADU of 500 square feet or less. [1]

Since 2026 this rule has lived in Section 66311.5. Before that it was Section 66324, and many fee schedules still cite the old number. [1]

## How the 750 is measured

The threshold is expressed as *interior livable space*. The code defines livable space as space in a dwelling intended for human habitation, including living, sleeping, eating, cooking or sanitation. [1]

> **Tip:** That wording matters for a design sitting near the line. A plan labeled 760 square feet on the cover sheet may be measured to the outside of the walls. Ask your designer to state the interior livable area on the plans, and ask the city which figure its fee calculation uses, before you assume the fee applies.

## Units over 750 square feet

Go over the line and impact fees can be charged, but not at the full rate for a new house. They must be charged proportionately in relation to the square footage of the primary dwelling. [1]

> **Example:** Using made-up numbers: if a city's impact fee for a new home were $20,000 and your ADU is 900 square feet behind an 1,800 square foot house, a proportionate charge would be half, or $10,000. Cities apply the proportion in different ways, so treat this only as a way to sanity-check a quote.

## What isn't an impact fee

Don't expect a zero on every line of the fee estimate. Connection fees and capacity charges are carved out of the definition. [1] Plan check fees, permit fees and school fees are different charges again and are set by each agency.

## Why 800 and 850 also come up

Three similar numbers appear in ADU conversations and they do different jobs:

- **750** is the impact fee line described here. [1]
- **800** is the size a city's lot coverage, floor area ratio, open space and front setback rules must still allow, with four-foot side and rear setbacks. [2]
- **850** is the lowest maximum size a city may set, rising to 1,000 for a unit with more than one bedroom. [2]

Many owners settle on a plan just under 750 for the fee saving. Whether that trade is worth a smaller unit depends on the fee schedule where you live.

## Frequently asked questions

### Is an ADU of exactly 750 square feet exempt from impact fees?

Under the statute, yes: the bar applies to 750 square feet of interior livable space or less. [1] Some city handouts word it as less than 750, Sacramento's among them. [3] See [Sacramento's fees](https://www.lotlinepermits.com/california/sacramento/#fees) for how to handle that.

### Do I still pay school fees on a small ADU?

School fees are a separate charge from impact fees and are set locally. In the City of Los Angeles, for example, school district fees are required for ADUs larger than 500 square feet. [4] More on [Los Angeles fees](https://www.lotlinepermits.com/california/los-angeles/#fees).

### Are utility connection fees waived as well?

No. Connection fees and capacity charges fall outside the definition of an impact fee. [1] The position is different for unpermitted units built before 2020, where most of those charges are waived. [1] See [fees for unpermitted units](https://www.lotlinepermits.com/california/laws/unpermitted-adu-rules/#fees).

## References

1. California Government Code, Title 7, Division 1, Chapter 13, Article 1 (Sections 66310 to 66313.5). California Legislative Information. https://leginfo.legislature.ca.gov/faces/codes_displayText.xhtml?lawCode=GOV&division=1.&title=7.&part=&chapter=13.&article=1. (read 2026-11-10)
2. California Government Code, Title 7, Division 1, Chapter 13, Article 2 (Sections 66314 to 66331). California Legislative Information. https://leginfo.legislature.ca.gov/faces/codes_displayText.xhtml?lawCode=GOV&division=1.&title=7.&part=&chapter=13.&article=2. (read 2026-11-10)
3. CDD-0423: Accessory Dwelling Units (ADU) handout. City of Sacramento, Community Development Department. https://www.cityofsacramento.gov/content/dam/portal/cdd/Building/Forms/CDD-0423_Accessory-Dwelling-Units-(ADU)-Handout.pdf (read 2026-11-10)
4. ZA Memorandum No. 143: Implementation of 2019 Accessory Dwelling Unit (ADU) Ordinance and State ADU Law. City of Los Angeles, Department of City Planning and Department of Building and Safety. https://planning.lacity.gov/odocument/184600d8-71d7-4d74-baf1-1f9cd2603320/ZA_Memo_No_143.pdf (read 2026-11-10)

General information only, not legal advice. See https://www.lotlinepermits.com/disclaimer/