Research study
What an ADU costs in fees — and the cliff at 750 square feet
The rules are unambiguous and fully sourced. The schedules that put numbers on them are, as far as a machine can reach, unpublished.
Written by HyreADU Research Desk Primary-source research and data analysis
Audited by HyreADU Research Desk Statutory citation and retrieval-date audit
The finding
Below 750 square feet, a California ADU pays no impact fee at all — to anybody. Government Code section 66311.5(c)(1) bars any impact fee on an ADU of 750 square feet of interior livable space or less, or a JADU of 500 square feet or less.
Not just the city is bound, but special districts and water corporations too.
One square foot over, and the whole fee arrives on a formula. The same paragraph requires fees on an ADU above 750 square feet to be “charged proportionately in relation to the square footage of the primary dwelling unit.” Against a 2,000 square foot house, a 751 square foot ADU is charged at roughly 38 per cent of the primary dwelling’s impact fee, and a 1,200 square foot ADU at 60 per cent.
That is a cliff, not a slope, and it is the single most consequential number in ADU project design. Utility connection charges are treated separately, and more favorably still. Section 66311.5(b) provides that an ADU is not “a new residential use for purposes of calculating connection fees or capacity charges for utilities,” unless built with a new single-family dwelling, and section 66311.5(d) separately bars requiring a new or separate utility connection in the same circumstances.
Everything else runs through the Mitigation Fee Act: section 66311.5(a) routes ADU fees to Chapter 5 and Chapter 7, the source of the reasonable-cost limit at section 66013 and the publication duties at section 66016.
What this page does not have is a priced table by city, and the reason is worth publishing. Every municipal site and code platform we attempted returned HTTP 403 to automated retrieval.
The agencies under a statutory duty to publish their cost data could not be read by machine on this date. The attempt log is published below rather than filled with numbers from commercial sources. Not legal or financial advice.
Read this first
- There is no priced per-city table on this page, and we are not pretending otherwise
The contract for this page called for two model ADUs priced against every published fee schedule in the sample, itemized with adoption dates. We could not retrieve a single municipal fee schedule.
Rather than substitute figures from ADU-marketing sites — which are undated, unsourced and frequently years stale — we have published the statutory architecture in full, the arithmetic that architecture forces, and a table of exactly what we attempted and what each attempt returned.
A fee figure you cannot trace to an adopted schedule with a date is worse than no figure.
- This is not legal or financial advice, and fees are jurisdiction-specific by design
Impact fees are set by individual agencies under the Mitigation Fee Act and vary enormously between neighboring cities. Nothing on this page tells you what your project will pay.
What it does tell you is which fees may lawfully be charged at all, which are barred, and what questions produce a documented answer at the counter.
- The proportionality percentages on this page depend on your house, not on your city
The statutory formula charges an over-750 ADU “proportionately in relation to the square footage of the primary dwelling unit”.
So the same 900 square foot ADU is charged at 45 per cent of the primary dwelling fee behind a 2,000 square foot house and 30 per cent behind a 3,000 square foot house.
Every percentage on this page uses an illustrative 2,000 square foot primary dwelling, stated every time. Substitute your own number before using any of them.
- “Impact fee” is a narrower term than “fees”
The 750 square foot bar is specifically about impact fees. It does not exempt a project from plan check fees, building permit fees charged as cost recovery for the review itself, school fees where the assessable space threshold is exceeded, or the utility work required to serve the unit.
A sub-750 ADU is not free. It is free of one specific and usually large category.
Why fees, and not construction cost, decide small ADU projects
Construction cost scales roughly with size. Fees do not. Under the Mitigation Fee Act, an impact fee is a contribution toward the public facilities a new dwelling is deemed to burden — parks, schools, roads, sewer capacity — and before 2019 the common practice was to charge an ADU as a dwelling unit, at or near the same rate as a house.
On a 500 square foot unit that could be a five-figure charge attached to a project whose whole construction budget was low six figures.
The Legislature’s answer was not to reduce the fee. It was to remove the category below a size threshold and prorate it above one. That is a blunt instrument, and blunt instruments produce cliffs.
HyreADU analysis: the cliff at 750 square feet is, in our view, the most under-discussed design constraint in California ADU work, and it is under-discussed because the fee schedules that would quantify it are so hard to obtain.
The decision between a 740 square foot two-bedroom and an 820 square foot two-bedroom is not a decision about eighty square feet of construction.
It is a decision about whether a proportional share of the full impact fee schedule attaches to the project at all. Everyone designing ADUs at that boundary should know the number, and almost nobody can look it up.
The fee architecture, by fee type
Which fees may be charged on an ADU, which may not, and under what authority. Every row is quoted from the statute as retrieved on 2026-09-05.
| Fee type | May it be charged on an ADU? | Authority and operative text | Currency |
|---|---|---|---|
| Impact fees — ADU of 750 sq ft or less | No. Prohibited outright. | “A local agency, special district, or water corporation shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less.” Gov. Code § 66311.5(c)(1). Note the three classes of body bound. | Added by renumbering § 66324 by Stats. 2025, Ch. 520, Sec. 7 (SB 543), effective 1 January 2026. |
| Impact fees — JADU of 500 sq ft or less | No. Prohibited outright. | Same sentence: “… or a junior accessory dwelling unit that has 500 square feet of interior livable space or less.” Since a JADU is by definition “no more than 500 square feet of interior livable space” (§ 66313(d)), every compliant JADU is inside the bar. | Same section. |
| Impact fees — ADU over 750 sq ft | Yes, but only proportionately. | “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.” Gov. Code § 66311.5(c)(1). | Same section. |
| Utility connection fees and capacity charges | Generally no — the unit is not a new residential use. | An ADU or JADU “shall not be considered by a local agency, special district, or water corporation to be a new residential use for purposes of calculating connection fees or capacity charges for utilities, including water and sewer service, unless the unit was constructed with a new single-family dwelling.” Gov. Code § 66311.5(b). | Same section. |
| A required new or separate utility connection | Generally may not be required. | The agency “shall not require the applicant to install a new or separate utility connection directly between the unit and the utility or impose a related connection fee or capacity charge, unless the unit was constructed with a new single-family dwelling.” Gov. Code § 66311.5(d). | Same section. |
| Connection fees and capacity charges where they are chargeable | Yes, but capped at cost. | “Fees or charges shall not exceed the estimated reasonable cost of providing the service”, absent two-thirds voter approval. A capacity charge covers existing or new public facilities providing proportional benefit; a connection fee covers the physical infrastructure — meters, boxes, pipelines — with costs bearing a fair relationship to the burdens or benefits. Gov. Code § 66013. | Amended by Stats. 2020, Ch. 370, Sec. 180 (SB 1371), effective 1 January 2021. |
| School facilities fees | Only above an assessable space threshold. | The levy applies to residential construction “only if the resulting increase in assessable space exceeds 500 square feet”. Ed. Code § 17620(a)(1)(C)(i). A JADU, capped at 500 square feet of interior livable space, does not exceed that threshold on its face. | Amended by Stats. 2010, Ch. 541, Sec. 1 (AB 2048), effective 1 January 2011. |
| Any fee, on legalizing a pre-2020 unpermitted unit | No impact fees, no connection or capacity charges. | The applicant “shall not be required to pay impact fees or connection or capacity charges except when utility infrastructure is required to comply with Section 17920.3 of the Health and Safety Code and when the fee is authorized by subdivision (e) of Section 66311.5.” Gov. Code § 66311.7(e). | Added by renumbering § 66332 by Stats. 2025, Ch. 520, Sec. 9 (SB 543), effective 1 January 2026. See our legalization study. |
| Plan check and building permit fees | Yes, as cost recovery. | Not addressed by the ADU-specific bar. Section 66311.5(a) routes ADU fees generally to Chapter 5 (commencing with § 66000) and Chapter 7 (commencing with § 66012) — the Mitigation Fee Act framework, under which such fees are cost-recovery rather than impact charges. | Gov. Code § 66311.5(a). |
Which fees may lawfully be charged on a California accessory dwelling unit. Source: California Government Code and Education Code, retrieved from leginfo.legislature.ca.gov on 2026-09-05.
HyreADU note on citation, and it matters here more than almost anywhere. The fee section is one of the two provisions SB 543 renumbered.
It was Gov. Code § 65852.2(f) until March 2024, then § 66324, and has been § 66311.5 since 1 January 2026.
Fee schedules, staff reports and permit software written against § 66324 are citing a number that no longer exists, and a great deal of published guidance still cites § 65852.2(f).
The 750 square foot cliff, drawn
The single most consequential piece of arithmetic in ADU project design, and one almost nobody can price because the schedules are not reachable.
What the statute actually says, and what it leaves open
Fact. The bar is absolute below the threshold and binds three classes of body: “A local agency, special district, or water corporation shall not impose any impact fee”. The word “any” is doing real work — it is not a reduction or a cap, it is a prohibition on the category.
What is left open: the statute says impact fees above the threshold “shall be charged proportionately in relation to the square footage of the primary dwelling unit”, and does not spell out the arithmetic beyond that phrase.
The natural reading, and the one every source we found uses, is the ratio of ADU square footage to primary dwelling square footage applied to the fee the primary dwelling would bear.
We have used that reading and labeled it. It is not a formula written out in the section.
Why the cliff is bigger than the numbers on the chart suggest
The chart shows the proportion, not the amount. The amount depends on the underlying impact fee schedule — parks, traffic, sewer capacity, school facilities and whatever else the agency has adopted — and those schedules in high-fee California jurisdictions run to tens of thousands of dollars per dwelling.
HyreADU analysis: which means the practical decision at the boundary is between zero and a share of a number that can be comparable to a substantial fraction of the ADU’s construction budget.
It is entirely rational, on those terms, for a designer to hold a unit at 750 square feet even where the client wants 850.
Whether that is good housing policy is a separate question; that it is the incentive the statute creates is arithmetic.
Interior livable space, not gross floor area
The threshold is expressed in “interior livable space”, and section 66313(e) defines livable space as “a space in a dwelling intended for human habitation, including living, sleeping, eating, cooking, or sanitation”.
That is not the same measure as gross floor area, and it is not the same measure a building department may use elsewhere on the same plan set.
HyreADU recommendation: at the boundary, get the measurement basis confirmed in writing before the plan set is finalized. A project designed to 748 square feet on one measure and assessed at 762 on another has lost the exemption on a drafting convention.
The proportionality formula, worked
HyreADU calculation on the statutory formula, against an illustrative 2,000 square foot primary dwelling. Substitute your own primary dwelling size: the ratio is the whole formula.
| ADU interior livable space | Impact fee permitted? | Proportion of the primary dwelling’s impact fee | Basis |
|---|---|---|---|
| 500 sq ft | No — prohibited | 0% | Gov. Code § 66311.5(c)(1): no impact fee on an ADU of 750 sq ft of interior livable space or less. |
| 750 sq ft | No — prohibited | 0% | Gov. Code § 66311.5(c)(1): no impact fee on an ADU of 750 sq ft of interior livable space or less. |
| 800 sq ft | Yes, proportionately | 40% | 800 ÷ 2,000 = 0.400. HyreADU calculation on the § 66311.5(c)(1) proportionality formula. |
| 900 sq ft | Yes, proportionately | 45% | 900 ÷ 2,000 = 0.450. HyreADU calculation on the § 66311.5(c)(1) proportionality formula. |
| 1,000 sq ft | Yes, proportionately | 50% | 1000 ÷ 2,000 = 0.500. HyreADU calculation on the § 66311.5(c)(1) proportionality formula. |
| 1,200 sq ft | Yes, proportionately | 60% | 1200 ÷ 2,000 = 0.600. HyreADU calculation on the § 66311.5(c)(1) proportionality formula. |
| 751 sq ft — the first taxable square foot | Yes, proportionately | 38% | 751 ÷ 2,000 = 0.376. The discontinuity: one square foot above the threshold moves the project from a statutory prohibition to roughly 38 per cent of the full fee. |
Impact fee proportion by ADU size, against a 2,000 square foot primary dwelling. HyreADU calculation applying the formula in Gov. Code § 66311.5(c)(1) as retrieved on 2026-09-05. Not a dollar figure and not a quotation from any fee schedule.
Two cautions. First, the proportion moves with your house: behind a 3,000 square foot primary dwelling the 900 square foot row is 30 per cent, not 45 per cent.
Second, the statute states the principle (“proportionately in relation to the square footage of the primary dwelling unit”) without writing out the arithmetic; the ratio used here is the natural reading and is labeled as our calculation, not as statutory text.
What we tried, and what came back
Published because it is the finding. Three of these bodies are under statutory duties to make fee cost data publicly available, and none of them could be read by machine on this date.
| What we attempted | Result on 2026-09-05 | What that blocks |
|---|---|---|
| City planning and building department fee pages (Los Angeles, San José among them) | HTTP 403 Forbidden. Automated retrieval refused; no response body returned. | Every per-jurisdiction fee figure. Plan check, building permit, park, traffic and utility connection schedules. |
| library.municode.com — the platform hosting most California municipal codes | HTTP 403 Forbidden on every attempt. Mirror hosts timed out across five attempts. | Codified fee provisions, ordinance numbers and adoption dates. |
| hcd.ca.gov — California Department of Housing and Community Development | HTTP 403 with a “scheduled maintenance” notice, for the whole retrieval session. | HCD technical assistance memoranda, ordinance review correspondence and any ADU Handbook edition later than January 2025. |
| Web search, to discover alternative URLs for fee schedules | Unavailable. The session budget was exhausted at 200 of 200 calls before this page was researched. | Discovery of any fee schedule whose URL we could not construct from first principles. This is why the sample is not merely small but effectively zero. |
| leginfo.legislature.ca.gov — the Legislative Counsel’s code service | Worked, on every request. | Nothing. This is why the statutory half of this page is complete and fully quoted, and the municipal half is empty. |
Retrieval attempts and outcomes for California ADU fee data, 2026-09-05. Recorded so that the absence of a priced table on this page is auditable rather than unexplained.
HyreADU analysis, and we want to state it carefully. A 403 to an automated client is not evidence of an agency concealing anything, and these documents are in most cases available to a person with a browser.
But Government Code section 66016 requires an agency, before adopting or increasing a fee, to make available “data indicating the amount of cost, or estimated cost, required to provide the service” at least ten days before the meeting, and section 66013 requires connection fee and capacity charge information to be made available within 180 days after each fiscal year.
Those are duties to publish. A publication regime that is functionally unreadable by automated retrieval, in 2026, is one that cannot be audited at scale — and the practical consequence is that the comparative fee analysis California ADU applicants most need does not exist anywhere, including here.
How to get your actual number
Since we cannot give it to you, here is the method that gets it, in the order that works. Steps two and three rest on statutory duties, so they are requests the agency is obliged to meet.
- 1 Fix the interior livable space figure first, and get the measurement basis agreed
Everything else follows from whether the unit is at or below 750 square feet of interior livable space.
Section 66313(e) defines livable space as “a space in a dwelling intended for human habitation, including living, sleeping, eating, cooking, or sanitation”.
Confirm in writing how the building department measures it against your plan set before you finalize the design.
- 2 Ask for the adopted fee schedule and the resolution number that adopted it
Not the handout, not the estimator — the adopted schedule, with the resolution or ordinance number and the adoption date.
That is the document that governs, and it is the only one worth putting in a project budget.
Section 66016 requires the underlying cost data to have been made publicly available before adoption, so ask for that too.
- 3 Ask the water and sewer providers separately, because they are separately bound
Section 66311.5 binds “a local agency, special district, or water corporation”. Your water and sewer service may come from a district that is not the city and that runs its own schedule.
Section 66311.5(b) says the ADU is not a new residential use for connection fee or capacity charge purposes unless built with a new single-family dwelling — quote that subdivision to the district in writing, by its current number.
- 4 Ask the school district whether the assessable space threshold is exceeded
Education Code section 17620(a)(1)(C)(i) applies the levy “only if the resulting increase in assessable space exceeds 500 square feet”. That threshold is separate from, and lower than, the 750 square foot impact fee threshold, so a 700 square foot ADU can be inside the impact fee bar and outside the school fee threshold at once.
- 5 Check the invoice against the statute, line by line, and cite the current number
This is the step that recovers money. Fee software and printed schedules do not always reflect the current statute, and the fee section has been renumbered twice since 2024.
If a line item is an impact fee on a sub-750 square foot unit, or a capacity charge on a unit not built with a new single-family dwelling, section 66311.5 is the answer — and cite it as § 66311.5, not § 66324 or § 65852.2(f).
- 6 If you are legalizing an existing unit, invoke § 66311.7(e) explicitly
A pre-2020 unpermitted unit carries its own waiver: no impact fees and no connection or capacity charges, with one narrow utility-infrastructure exception. It is a different provision from the one above and it is easy for a counter to miss.
Four terms that change the answer
- Impact fee
- A charge imposed on new development toward the cost of public facilities it is deemed to burden, adopted under the Mitigation Fee Act (Gov. Code § 66000 et seq.). It is the category the 750 square foot bar removes. It is not a plan check fee or a building permit fee, which are cost recovery for the review work itself and are not covered by the bar.
- Capacity charge
- Per Gov. Code § 66013, a charge for existing or planned public facilities providing a proportional benefit, including supply contracts and capital-related rights, and excluding commodity charges. Distinct from a connection fee, which covers the physical infrastructure — meters, boxes, pipelines — needed to connect. Section 66311.5(b) reaches both.
- Interior livable space
- The measure the 750 and 500 square foot thresholds are expressed in. Section 66313(e) defines livable space as “a space in a dwelling intended for human habitation, including living, sleeping, eating, cooking, or sanitation”. Not gross floor area, and worth confirming against your building department’s practice before the design is fixed.
- Assessable space
- The Education Code measure for school facilities fees. Section 17620(a)(1)(C)(i) applies the levy only where “the resulting increase in assessable space exceeds 500 square feet” — a different threshold, on a different measure, from the impact fee bar in the Government Code.
What we could not verify
Every municipal fee schedule. Named at the top, logged in a table, and named again here because it is the central limitation of this edition. No dollar figure for any jurisdiction appears anywhere on this page.
The exact arithmetic the proportionality formula requires. The statute states the principle — “charged proportionately in relation to the square footage of the primary dwelling unit” — and does not write out the calculation.
We have used the ratio reading, which is the natural one and the one every source we encountered uses, and labeled it as our calculation rather than as statutory text. An agency applying a different construction is not obviously wrong on the face of the section.
HCD’s technical assistance memoranda on fees. hcd.ca.gov returned HTTP 403 and a scheduled-maintenance notice for the whole retrieval. If HCD has issued guidance on the proportionality calculation, it would settle the previous paragraph, and it is the first thing to check in the next edition.
CPUC-filed utility tariff rules. The contract for this page anticipated pricing electric and water utility tariff rules on new service, capacity and connection charges.
We did not reach the CPUC tariff filings and no tariff figure appears here.
The statutory position under §§ 66311.5(b) and (d) and § 66013 is set out; the tariffs that would put numbers on the residual cases are not.
Whether any jurisdiction is charging an impact fee on a sub-750 square foot unit. The contract anticipated characterizing any such case against HCD guidance rather than declaring it unlawful ourselves.
We found no such case, because we could not read any fee schedule — an absence of evidence, not evidence of compliance. We name no jurisdiction on this page for anything.
Adoption dates for anything municipal. The E-E-A-T requirement for this page is a per-record source URL and retrieval date with adoption dates on the schedules. We can meet that standard for every statutory row and for none of the municipal ones, which is precisely why there are no municipal rows.
Questions
Do I have to pay impact fees on an ADU in California?
What happens at exactly 751 square feet?
Do I have to pay a water or sewer connection fee for an ADU?
Which Government Code section covers ADU fees?
Why does this page not list fees by city?
Are school fees charged on an ADU?
Do I pay fees to legalize an unpermitted ADU?
Is a sub-750 square foot ADU free of all fees?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of Government Code §§ 66311.5, 66013 and 66016, Education Code § 17620 and Government Code § 66311.7 retrieved from leginfo.legislature.ca.gov 2026-09-05; municipal fee schedule retrieval attempted and logged on the same date. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- California Government Code § 66311.5 — ADU fees, the 750 square foot impact fee bar, and utility connection treatment , The central provision on this page. Retrieved 2026-09-05. (a): fees “shall be determined in accordance with Chapter 5 (commencing with Section 66000) and Chapter 7 (commencing with Section 66012).” (b): an ADU or JADU “shall not be considered by a local agency, special district, or water corporation to be a new residential use for purposes of calculating connection fees or capacity charges for utilities, including water and sewer service, unless the unit was constructed with a new single-family dwelling.” (c)(1): “A local agency, special district, or water corporation shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less or a junior accessory dwelling unit that has 500 square feet of interior livable space or less”, and “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.” (d): the agency “shall not require the applicant to install a new or separate utility connection directly between the unit and the utility or impose a related connection fee or capacity charge, unless the unit was constructed with a new single-family dwelling.” Enactment line: “Added by renumbering Section 66324 by Stats. 2025, Ch. 520, Sec. 7. (SB 543) Effective January 1, 2026.” Retrieved 2026-09-05.
- California Government Code § 66013 — connection fees and capacity charges limited to reasonable cost , Retrieved 2026-09-05. “Fees or charges shall not exceed the estimated reasonable cost of providing the service” absent two-thirds voter approval. Defines a capacity charge as covering existing or new public facilities providing proportional benefit, including supply contracts and capital-related rights but excluding commodity charges; and a connection fee as covering the physical infrastructure — meters, boxes and pipelines — where labor and material costs bear a fair relationship to the payor’s burdens or benefits. Requires agencies to make available, within 180 days after each fiscal year, charge descriptions, fund balances, collection amounts, improvement expenditures, completed projects and interfund transfer details. Amended by Stats. 2020, Ch. 370, Sec. 180 (SB 1371), effective 1 January 2021. Retrieved 2026-09-05.
- California Government Code § 66016 — notice and cost data before adopting or increasing a fee , Retrieved 2026-09-05. Notice of the time and place of the meeting “shall be mailed at least 14 days prior to the meeting”; “[a]t least 10 days prior to the meeting, the local agency shall make available to the public data indicating the amount of cost, or estimated cost, required to provide the service”, together with “the revenue sources anticipated to provide the service, including General Fund revenues”; and the agency “shall hold at least one open and public meeting, at which oral or written presentations can be made, as part of a regularly scheduled meeting.” Amended by Stats. 2006, Ch. 643, Sec. 19, effective 1 January 2007. Cited on this page as the publication duty against which the retrieval log should be read. Retrieved 2026-09-05.
- California Education Code § 17620 — school facilities fees and the 500 square foot assessable space threshold , Retrieved 2026-09-05. Subdivision (a)(1)(B) authorizes the governing board to levy fees “To new residential construction”; (a)(1)(C)(i) applies fees to residential construction “only if the resulting increase in assessable space exceeds 500 square feet”; (a)(1)(C)(ii) cross-references the Revenue and Taxation Code § 74.3 exclusion, which on retrieval concerns accessibility modifications for a severely and permanently disabled person and is not an ADU provision. Amended by Stats. 2010, Ch. 541, Sec. 1 (AB 2048), effective 1 January 2011. Retrieved 2026-09-05.
- California Government Code § 66311.7 — no impact fees or connection charges when legalizing a pre-2020 unit , Retrieved 2026-09-05. Subdivision (e): the homeowner “shall not be required to pay impact fees or connection or capacity charges except when utility infrastructure is required to comply with Section 17920.3 of the Health and Safety Code and when the fee is authorized by subdivision (e) of Section 66311.5.” Enactment line: “Added by renumbering Section 66332 by Stats. 2025, Ch. 520, Sec. 9. (SB 543) Effective January 1, 2026.” Retrieved 2026-09-05.
- California Government Code § 66313 — definitions of livable space and junior accessory dwelling unit , Retrieved 2026-09-05. Subdivision (e): livable space is “a space in a dwelling intended for human habitation, including living, sleeping, eating, cooking, or sanitation” — the measure in which the 750 and 500 square foot thresholds are expressed. Subdivision (d): a JADU is “a unit that is no more than 500 square feet of interior livable space in size and contained entirely within a single-family residence.” Amended by Stats. 2025, Ch. 520, Sec. 2 (SB 543), effective 1 January 2026. Retrieved 2026-09-05.
- SB 543 (McNerney, 2025) — Accessory dwelling units. Stats. 2025, Ch. 520 , Chaptered 10 October 2025, operative 1 January 2026. Section 7 amends and renumbers § 66324 to § 66311.5 — the fee section this page is about. The reason any fee citation to § 66324 or to former § 65852.2(f) no longer resolves. Retrieved 2026-09-05.
Know which side of 750 square feet you are on
Below the line, no impact fee may be imposed by the city, a special district or a water corporation. Above it, a proportional share of the whole schedule attaches.
Fix the interior livable space figure and the measurement basis before the plan set is final — it is the cheapest decision in the project and the most expensive one to get wrong.
HyreADU does not design, permit or build accessory dwelling units, does not practice law and does not provide financial advice. This page is informational and is not legal or financial advice.
It describes California statutory text as retrieved on 5 September 2026 and contains no fee figure for any jurisdiction, because no municipal fee schedule could be retrieved on that date — the full attempt log is published on the page.
Percentages shown are HyreADU arithmetic applying the statutory proportionality principle against an illustrative primary dwelling size stated with every figure; they are not dollar amounts and not quotations from any adopted schedule.
The statute states the proportionality principle without writing out the calculation, and an agency may construe it differently. Fees are set by individual agencies and vary widely between neighboring jurisdictions.
The useful next step is the adopted fee schedule with its resolution number, requested in writing, from the city and from each water and sewer provider separately.