Senate Bill 1117 (Cervantes, Chapter 809 of 2026) was signed on September 29, 2026 and takes effect on January 1, 2027. For up to two ADUs on a lot, it removes the fee cliff at 750 square feet: an ADU larger than 750 square feet is charged impact fees only on the area above that line, not on the whole unit. This page sets out what the chaptered text says and what it leaves alone.
Impact fees are the one-off charges a city, special district or water corporation levies on new development for parks, roads and other public facilities. Government Code section 66311.5 already bars any impact fee on an ADU with 750 square feet of interior livable space or less, and on a junior ADU of 500 square feet or less.
Above 750 square feet the old rule charged the whole unit, in proportion to the size of the primary dwelling. One extra square foot could make the entire ADU chargeable.
SB 1117 rewrites that sentence. From January 1, 2027: "For up to two accessory dwelling units on a lot, any impact fees charged for an accessory dwelling unit that has more than 750 square feet of interior livable space shall be charged proportionately in relation to the square footage of the primary dwelling unit, and only on the area in excess of 750 square feet of interior livable space."
The statute does not prescribe the arithmetic, and agencies apply "proportionately" in different ways. The figures below are made up to show the size of the change under one common method, where the ADU is charged the share of a single-family fee that matches its size relative to the house.
Take a 2,000 square foot house in a city whose impact fees for a new house total $20,000, and a 1,000 square foot ADU. Charged on the whole unit, the ADU is half the size of the house, so the fee is $10,000. Charged only on the 250 square feet above the line, it is one-eighth the size of the house, so the fee is $2,500.
Your city's fee schedule and method will differ. Ask for the calculation in writing before you settle on a size.
The section defines "impact fee" as a fee under the Mitigation Fee Act, Government Code section 66000, plus park fees under section 66477. It then says what is left out: "Impact fee does not include any connection fee or capacity charge charged by a local agency, special district, or water corporation."
Utility connections have their own rules in the same section. For an ADU or junior ADU described in Government Code section 66323(a)(1), meaning one within the existing or proposed space of a single-family home or within an existing accessory structure, an agency cannot require a new or separate utility connection or charge a related connection fee, unless the unit was constructed with a new single-family dwelling or upon separate conveyance of the ADU under Section 66342. For other ADUs an agency may require a separate connection, with a fee proportionate to the burden of the unit, based on its square footage or its plumbing fixtures, and no more than the reasonable cost of the service.
School fees follow a different line. An ADU or junior ADU with less than 500 square feet of interior livable space is treated, for Education Code section 17620 purposes, as not increasing assessable space by 500 square feet. SB 1117 does not change that.
The new method covers "up to two accessory dwelling units on a lot". For a property with more than two, the statute keeps the old approach: fees on an ADU larger than 750 square feet are charged proportionately to the primary dwelling, without the above-750 limit.
The bill caps how impact fees are calculated. It does not require any agency to charge them, and it does not limit building-permit or plan-check fees, which are separate.
The text does not say which date fixes the fee for a project already under way on January 1, 2027. Ask your city whether it applies the new method by application date, permit issuance or another milestone.
It mainly helps owners planning an ADU larger than 750 square feet on a lot with no more than two ADUs, where the agency charges impact fees. Under the old rule the difference between 750 and 800 square feet could be thousands of dollars in fees. From 2027, on a lot with no more than two ADUs, the extra 50 square feet is the only ADU area used for the impact-fee calculation.
It also fits with AB 956, which from the same date requires cities to approve two detached ADUs on a single-family lot. Both units fall within "up to two accessory dwelling units on a lot".
This page summarises the statute. It is not legal advice, and a city's reading of a new law can differ in the first months. Ask your planning or building department for its position in writing before you spend money on plans.
January 1, 2027. The Governor signed it on September 29, 2026 as Chapter 809 of the Statutes of 2026. It is an ordinary, non-urgency statute.
From January 1, 2027, for up to two ADUs on a lot, any impact fees may be charged only on the area above 750 square feet of interior livable space, and in proportion to the size of the primary dwelling. An ADU of 750 square feet or less remains exempt from impact fees.
No. Connection fees and capacity charges are excluded from the definition of impact fee and have their own rules in Government Code section 66311.5.
No. School fees are governed by Education Code section 17620. An ADU or junior ADU with less than 500 square feet of interior livable space is treated as not increasing assessable space by 500 square feet.
The above-750 limit applies to up to two ADUs on a lot. For a property with more than two, impact fees on an ADU larger than 750 square feet are charged proportionately to the primary dwelling under the older method.