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State law

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.

At a glance

750 sq ft
or less of interior livable space: no impact fee1
500 sq ft
or less for a junior ADU: no impact fee1
850 sq ft
the lowest maximum size a city may set2

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

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

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.

Common 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 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.

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.

Keep reading

About this page

Written by
The Lotline Editorial Team. Editorial policy
Where it comes from
We wrote this from material published by California Legislative Information and City of Sacramento and City of Los Angeles. You'll find each document, and the part we used, under References below.
How it was checked
Before publishing, we checked each statement against the original wording of its source. How we work
Last reviewed
. Rules and city procedures change, so confirm current requirements with your permitting agency.
Corrections
Email support@lotlinepermits.com. We check every report against the document and fix what is wrong.

References

  1. 1California Government Code, Title 7, Division 1, Chapter 13, Article 1 (Sections 66310 to 66313.5)California Legislative Information. Read on November 10, 2026.Cited: § 66311.5(c)(1); § 66311.5(c)(2); § 66311.5, amendment note; § 66313(e); § 66311.7(e).
  2. 2California Government Code, Title 7, Division 1, Chapter 13, Article 2 (Sections 66314 to 66331)California Legislative Information. Read on November 10, 2026.Cited: § 66321(b)(2); § 66321(b)(3).
  3. 3CDD-0423: Accessory Dwelling Units (ADU) handoutCity of Sacramento, Community Development Department. Dated January 29, 2026. Read on November 10, 2026.Cited: page 2, Building Permit Fees and Impact Fees.
  4. 4ZA Memorandum No. 143: Implementation of 2019 Accessory Dwelling Unit (ADU) Ordinance and State ADU LawCity of Los Angeles, Department of City Planning and Department of Building and Safety. Dated December 30, 2024. Read on November 10, 2026.Cited: page 9, Impact Fees.

General information, not legal advice. Read the disclaimer.