SB 1117: Should You Wait Until January to Permit Your ADU?

Numbers below are computed from the site’s verified fee data at 800 sq ft, re-verified 2 November 2026. Flat-fee conversions are marked unknown wherever the city has not published them.

The rule, in one paragraph

SB 1117 (Chapter 809, Statutes of 2026, signed September 29, 2026) amends only Government Code §66311.5. From January 1, 2027 — the default effective date for a non-urgency chaptered bill — it changes how impact fees work for the first two ADUs on a lot: for an ADU over 750 square feet of interior livable space, the fee applies only to the square footage above 750, charged proportionately to the primary dwelling (§66311.5(c)(1)(B)). A third ADU on the same lot does not get the excess-only limit, though it is still charged proportionately under (c)(1)(C). The act states it applies to all cities, including charter cities, so a charter city cannot opt out. “Impact fee” as defined in (c)(2) does not include any connection fee or capacity charge, so those charges are outside the rule entirely. The question every ADU owner is asking right now — permit in 2026, or wait until January — comes down to one thing: how much of your city’s impact fee is per-square-foot, and how much is flat.

How the math works

Take Hemet. Its city development impact fee runs $8.647 per sq ft. For an 800 sq ft ADU under the 2026 rules, that is $8.647 × 800 = $6,918. From January 1, 2027, only the 50 sq ft above 750 is taxable, so the same line becomes $8.647 × 50 = $432. Waiting saves $6,485 on that one line.

That calculation only works for per-square-foot lines. Most cities do not charge that way.

The cities where we can give you a number

These are the jurisdictions where the savings at 800 sq ft can be computed from verified per-square-foot impact lines. Only impact fees are shown; school fees, permit fees, and utility charges do not change under SB 1117.

Method: verified impact-fee lines only, 800 sq ft detached ADU, per-square-foot lines scaled to the 50 sq ft above 750. The ”?” means the city’s flat impact fees are added on top once the city publishes its conversion — the savings figure excludes them. That is why the savings column does not equal the 2026 column minus the 2027 column for Napa and Pacifica: their savings figures count only the per-square-foot lines. Napa and Pacifica each carry flat lines whose January treatment is unknown, so their real savings could be higher.

Check your own city in the calculator — the comparison block now shows 2026 vs 2027 side by side:

• Hemet: /compare/?jurisdiction=HEMET&sqft=800
• Upland: /compare/?jurisdiction=UPLAND&sqft=800
• Redlands: /compare/?jurisdiction=REDLANDS&sqft=800
• Napa: /compare/?jurisdiction=NAPA&sqft=800

The cities where nobody can give you a number yet

Of the 103 verified impact-fee lines in our data, 84 are flat amounts — a single dollar figure per dwelling, not a per-square-foot rate. SB 1117 says the fee applies only to the area above 750, but it does not say how a flat fee converts. Until each city publishes its method, any January savings figure for these cities would be a guess, and we do not guess.

The flat amounts waiting on a conversion include the biggest cliffs in the state:

If your city is on this list, the January savings could be large — Ontario’s flat fee is $37,595 in the General City area schedule or $58,576 in Ontario Ranch, and a parcel pays one area’s schedule, not both, so either figure, in principle, is on the table — or the city could adopt a conversion that preserves most of it. Nobody knows yet. That uncertainty is itself the story: the cities with the most to lose from SB 1117 are the ones that have said the least about how they will implement it.

Waiting is not free

A fee comparison is not a recommendation to wait. Fee schedules adjust every fiscal year — several cities index to CPI — so the 2026 rates in this post may not be the rates in effect when you pull a permit. Delay costs money in other ways: financing, contractor scheduling, and months of rent or housing you do not have. With about 60 days to January 1, a permit applied for in December may still be in review when the rules change — and which schedule applies then is a question for your city, not something this post assumes. Run the numbers for your city, then weigh them against what waiting costs you. If the savings are $6,485 in Hemet, waiting might pay. If your city’s impact fees are already $0 at your size, waiting buys nothing.

What to ask your city

If your city charges a flat impact fee, the single most useful question you can ask its planning counter is: “How will you convert the flat ADU impact fee to the SB 1117 excess-area basis on January 1?” A second question matters just as much if you apply in December: “Is the impact fee set by the date I apply, or the date the permit is issued?” If your application is still in review on January 1, the answer decides which schedule you pay. When cities answer, we will update the calculator the same week. After January 1, we will publish a follow-up with what actually changed — city by city, with the same source links.

FAQs

Does SB 1117 change school fees? No. School district developer fees are levied under Education Code §17620, a separate regime that SB 1117 does not amend.

Does it apply to a third ADU? The excess-only limit covers the first two ADUs on a lot. A third ADU on the same lot does not get that limit, though it is still charged proportionately under §66311.5(c)(1)(C).

What about water and sewer connection charges? Excluded. The §66311.5(c)(2) definition of “impact fee” does not include any connection fee or capacity charge, so those charges are outside the rule.

My ADU is 750 sq ft or smaller. Does anything change? No. Impact fees are already $0 at 750 sq ft or less under current law, so SB 1117 changes nothing at that size.

Where does the calculator show this? On /compare/: pick your jurisdiction and size, and the SB 1117 block below the totals shows the 2026 vs 2027 comparison for that city, with flat lines marked where conversion is not published.

Sources

• SB 1117, Chapter 809, Statutes of 2026 (chaptered text), California Legislative Information, checked 2 November 2026: https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202520260SB1117
• Gov. Code §66311.5, California Legislative Information: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66311.5
• All fee figures: the site’s verified fee data (fees.json), re-verified 2 November 2026; source documents are linked from each jurisdiction’s fee page.