SB 1117 Explained: ADU Impact Fees Above 750 Sq Ft (2027)

SB 1117 in One Paragraph

SB 1117 is Senate Bill 1117 of the 2025-2026 session, by Senator Cervantes. The Governor approved it on September 29, 2026, and it was chaptered that day as Chapter 809, Statutes of 2026. It amends one section, Government Code 66311.5, and takes effect January 1, 2027. Before SB 1117, an ADU of 750 square feet or less paid no impact fees, and a bigger one paid on its whole floor area. After SB 1117, a bigger ADU pays only on the square feet above 750, for up to two ADUs on a lot. The bill says it applies to charter cities too.

What SB 1117 Changes in the Impact Fee Formula

Here is the rule, in the statute’s words, Section 66311.5(c)(1)(B): for up to two ADUs on a lot, impact fees on an ADU over 750 square feet “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.”

Rule	Through December 31, 2026	From January 1, 2027	Section
ADU of 750 sq ft or less	No impact fee	No impact fee	66311.5(c)(1)(A)
JADU of 500 sq ft or less	No impact fee	No impact fee	66311.5(c)(1)(A)
ADU over 750 sq ft, one or two ADUs on the lot	Proportionate to the main house, on the whole ADU	Proportionate to the main house, only on the area above 750 sq ft	66311.5(c)(1)(B)
ADU over 750 sq ft, three or more ADUs on the lot	Proportionate, whole ADU	Unchanged: proportionate, whole ADU	66311.5(c)(1)(C)

The statute does not write out the arithmetic. The common way cities read “proportionately” is the ADU’s square footage divided by the main house’s, applied to what the city charges a new single-family home. Under SB 1117, that reading becomes:

Fee = city’s single-family impact fee x (ADU interior livable sq ft minus 750) / main house sq ft

Treat that formula as our illustration of the statutory wording, not a rule your city must use. Interior livable space is the measure SB 543 defined in Section 66313(e), so exterior walls do not count.

ADU Impact Fees Before and After SB 1117 (Worked Examples)

These examples use an 1,800 square foot main house and three common ADU sizes. Because cities publish different fee bases, the table shows the share of a city’s single-family impact fee the ADU pays, plus a dollar column for every $10,000 of single-family fee so you can scale it to your city. Every number is computed by the same helper the test suite checks.

The 800 square foot row is the one to look at. Under 2026 rules, going from 750 to 800 square feet flipped you from no fee to a fee on all 800 square feet. Under SB 1117 you pay on 50. Campbell is the clearest local example of the old cliff: its FY 2026-27 schedule charges a $9,328 park in-lieu fee on an ADU of 750 square feet or more and $0 below that. Campbell has not published a revised schedule for 2027 as of October 22, 2026, so we are not computing a new Campbell figure.

Which Fees SB 1117 Does and Does Not Cover

SB 1117 only changes “impact fees,” and the section defines that term narrowly. Here is what the text supports.

Charge	Does SB 1117 change it?	Why	Section
Impact fees (Mitigation Fee Act), including park fees under Section 66477	Yes: charged only on the area above 750 sq ft, for up to two ADUs	”Impact fee” means a Section 66000(b) fee, plus Section 66477 fees	66311.5(c)(1)(B), (c)(2)
Water and sewer connection fees and capacity charges	No	Expressly excluded from “impact fee.” Separate rules apply: a converted ADU generally cannot be charged a new connection fee, and other ADUs may be, proportionate to square feet or plumbing fixture units	66311.5(c)(2), (d), (e)
School fees	SB 1117 is silent	The section’s school paragraph ties school fees to Education Code 17620 and a 500 sq ft threshold, which SB 1117 did not describe changing	66311.5(c)(3)
Plan check and permit processing fees	No	Section 66000(b) excludes “fees for processing applications for governmental regulatory actions or approvals”	66000(b)
Taxes, such as a construction tax	No	Section 66000(b) covers monetary exactions “other than a tax”	66000(b)

So SB 1117 will not lower your building permit or plan check bill. For those, see our ADU permit cost guide.

Does SB 1117 Apply to Your ADU?

• Is the ADU more than 750 square feet of interior livable space? If not, you already pay no impact fees, and SB 1117 changes nothing for you.
• How many ADUs are on the lot? One or two: SB 1117 applies. Three or more: the old whole-unit rule still applies to any ADU over 750 square feet.
• Is it a JADU? A JADU of 500 square feet or less pays no impact fees, before or after.
• Is your city a charter city? It is covered. The bill includes a statewide-concern finding that applies it to charter cities.
• When is your fee assessed? This is the open question. SB 1117 does not say whether the 2027 rule turns on your application date, your permit issuance or when the city assesses the fee. If you are applying in late 2026 for an ADU over 750 square feet, ask your city in writing which date it uses.

How California Cities Charge ADU Impact Fees Today

This table pulls the published fee lines we already hold for each city, from each city’s own fee schedule, and sorts them by whether SB 1117 reaches them. We checked for SB 1117 guidance or a revised ADU fee schedule on October 22, 2026 and found none.

City / County	Status	Published fee line	Is it an impact fee SB 1117 changes?	Fee or timeline if published	Source	Our guide
Campbell	No revised schedule as of Oct 22, 2026	Park in-lieu fee, $0 under 750 sq ft, $9,328 at 750 sq ft or larger	Yes, the one impact-type fee in this list	FY 2026-27, effective July 1, 2026	Campbell Master Fee Schedule	Campbell ADU permits
Los Angeles	No SB 1117 guidance found as of Oct 22, 2026	Park fee (LAMC 12.33) and Affordable Housing Linkage Fee, $0 at any size	Already $0, so no change	Not applicable	Our Los Angeles permit page (LADBS and LAMC)	Los Angeles ADU permits
San Jose	No SB 1117 guidance found as of Oct 22, 2026	Building Division fee, $3,323 (0 to 750 sq ft) or $5,151 (751 to 1,200 sq ft)	No: a permit fee tier, not an impact fee	FY 2024-25 schedule, latest we could confirm	San Jose fee schedule	San Jose ADU permits
Los Altos	No SB 1117 guidance found as of Oct 22, 2026	$0 building permit and plan check; $0.42 per sq ft construction tax (LAMC Chapter 3.24)	No: a tax, outside the definition	FY 2025-26 schedule	Our Los Altos permit page	Los Altos ADU permits
Sunnyvale	No SB 1117 guidance found as of Oct 22, 2026	Plan check at 70% of the building permit fee; $268 Miscellaneous Plan Permit over 800 sq ft	No: processing fees	FY 2026-27 schedule	Sunnyvale Master Fee Schedule	Sunnyvale ADU permits
Santa Clara	No SB 1117 guidance found as of Oct 22, 2026	$306 flat Architectural Review / ADU fee	No: processing fee	Effective July 1, 2026	Our Santa Clara permit page	Santa Clara ADU permits
Berkeley	No SB 1117 guidance found as of Oct 22, 2026	$500 neighbor notification; $250 address assignment	No: processing fees	Not stated	Our Berkeley permit page	Berkeley ADU permits
Long Beach	No SB 1117 guidance found as of Oct 22, 2026	$115 processing fee; 6% technology and General Plan surcharges	No: processing fees	Not stated	Our Long Beach permit page	Long Beach ADU permits
Los Gatos	No SB 1117 guidance found as of Oct 22, 2026	$0 use and occupancy clearance	No: processing	Effective July 1, 2026	Our Los Gatos permit page	Los Gatos ADU permits
San Diego	No SB 1117 guidance found as of Oct 22, 2026	None held	Not published	Not published	Web search, Oct 22, 2026	San Diego ADU costs
Orange County (unincorporated)	No SB 1117 guidance found as of Oct 22, 2026	None held	Not published	Not published	Web search, Oct 22, 2026	Not covered yet

The pattern is the interesting part. Most of the dollar lines cities publish for ADUs are processing fees and permit tiers, which SB 1117 does not touch. The fees it does reach, park, traffic and facilities impact fees, are often buried in a separate development impact fee schedule, so check that schedule, not just the building permit page.

Cities did not love this bill. The City of La Verne’s April 2, 2026 opposition letter argued it further limits a city’s ability to recover the cost of new demand on local infrastructure and services.

Should You Size Your ADU Differently in 2027?

For years the rule of thumb was simple: stay at 750 square feet or under and skip impact fees entirely. SB 1117 turns that cliff into a slope. From January 1, 2027, going from 750 to 800 square feet adds a fee on 50 square feet, not 800.

That said, it is still a slope that points one way. At 1,000 or 1,200 square feet you still pay on 250 or 450 square feet, so the worked table above is worth running against your own main house. My honest take: design to the bedroom count you need and let the fee follow. If 800 square feet is what makes a real two-bedroom work, the fee penalty for that extra 50 is now small. Two things SB 1117 does not change are the 800 square foot size a city must allow for a detached ADU and the 850 or 1,000 square foot floors; see California ADU size limits.

How SB 1117 Fits With AB 956 and SB 543

• AB 956, also effective January 1, 2027, lets a single-family lot have two detached ADUs by right, each up to 800 square feet. That is exactly the “up to two ADUs on a lot” SB 1117 covers. Add a third ADU, say a garage conversion, and SB 1117’s lower formula stops applying to any unit over 750.
• SB 543 (2025) defined interior livable space at Section 66313(e) and moved the ADU fee rules to Section 66311.5. SB 1117 builds on both. Our California ADU law tracker covers SB 543 and every 2026 bill.
• SB 1211 lets a multifamily lot add up to eight detached ADUs. On a lot with more than two ADUs, the whole-unit fee rule in Section 66311.5(c)(1)(C) applies.
• For what an ADU costs to build at these sizes, see the 800 sq ft ADU cost guide, the 1,000 sq ft ADU cost guide and the California ADU cost page. For the full statewide rules, see the California ADU law and permits pillar.

Frequently Asked Questions

What is SB 1117 in California?

SB 1117 is a 2026 California law, Chapter 809, Statutes of 2026, that amends Government Code Section 66311.5. For up to two ADUs on a lot, it limits impact fees on an ADU over 750 square feet to the interior livable space above 750.

When does SB 1117 take effect?

January 1, 2027. The Governor approved SB 1117 on September 29, 2026, and it has no urgency clause. The statute does not say whether the date that matters is your application or when the fee is assessed, so ask your city.

Are ADUs under 750 square feet exempt from impact fees in California?

Yes. An ADU of 750 square feet or less of interior livable space, or a JADU of 500 square feet or less, pays no impact fees under Government Code Section 66311.5(c)(1)(A). That was true before SB 1117 and stays true after.

How do you calculate impact fees on an ADU?

An ADU over 750 square feet is charged in proportion to the main house’s square footage. From 2027, with one or two ADUs on the lot, only the square feet above 750 count. A common reading is the single-family fee times (ADU size minus 750) divided by the main house size.

What are the fees for an ADU permit in California?

Permit and plan check fees vary by city and are separate from impact fees. Our ADU permit cost guide lists published city fee lines. SB 1117 does not change permit processing fees.

Does SB 1117 reduce school fees or utility connection fees?

No. Connection fees and capacity charges are expressly excluded from the impact fees SB 1117 changes, and SB 1117 is silent on school fees, which follow Education Code 17620 and a 500 square foot threshold.

Does SB 1117 apply to a third ADU on my lot?

No. With more than two ADUs on a lot, any ADU over 750 square feet is still charged in proportion to the main house on its whole floor area, under Section 66311.5(c)(1)(C).

Sources

1. California Legislature, SB 1117 (2025-2026), chaptered bill text: https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202520260SB1117
2. California Legislature, SB 1117 (2025-2026), status (Chapter 809, Statutes of 2026): https://leginfo.legislature.ca.gov/faces/billStatusClient.xhtml?bill_id=202520260SB1117
3. California Government Code, Section 66311.5: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=66311.5.&lawCode=GOV
4. California Government Code, Section 66000 (definition of “fee”): https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=66000.&lawCode=GOV
5. City of Campbell, FY 2026-27 Master Fee Schedule: https://www.campbellca.gov/DocumentCenter/View/29705
6. City of La Verne, Opposition to SB 1117 (April 2, 2026): https://laverneca.gov/DocumentCenter/View/4888/Opposition-SB-1117

Disclaimer

This page is general information, not legal advice. SB 1117 takes effect January 1, 2027, and each city applies it through its own fee schedules. Confirm your fees, and the date your city uses, with your local planning department before you finalize a design.