Research
What an ADU actually costs to build in California
A range, and what moves you along it. Bid, survey average, declared permit valuation and a blog $/sf are four different numbers. This page keeps them apart.
Written by HyreADU Research Desk Primary-source research and data analysis
The finding
There is no sticker price for a California accessory dwelling unit, and a page that ships one is guessing.
The only statewide owner survey with a method — Chapple, Ganetsos and Lopez, UC Berkeley Center for Community Innovation, April 2021, of homeowners who permitted or completed an ADU in 2018 or 2019 — found a median construction cost of $150,000, or $250 per square foot, inclusive of design, labor, materials and permits.
Regional medians ran from $100,000 in Los Angeles County to $177,500 in the San Francisco Bay Area. Those are 2018–19 dollars, from owners who succeeded, and not a 2026 bid.
The Terner Center published a different statistic on a different basis, an average of $167,000. Average is not median, 2020 is not 2021, and both are set out below as theirs.
A construction-cost index can move a 2019 dollar; it cannot replace a survey. Indexing the survey median by the California Construction Cost Index gives about $230,351 in August 2026 dollars, or about 384 per square foot.
That is a HyreADU indexation of a 2018–19 owner survey, not a 2026 survey and not your invoice. Declared permit valuation is a third number and a lower one: contractor-named ADU permits in the City of Los Angeles carry a median declared valuation of $40,000, San Francisco’s $150,000.
Valuation is what the applicant wrote on the permit, not construction cost. Fees are a fourth, scaling with valuation or with floor area and turning on a 750-square-foot interior-livable-space threshold for impact fees under Government Code § 66311.5.
The five published schedules read here are a sample, not a census of California’s roughly 480 cities and counties. Nothing here is a quote, a bid, or a reason to build. HyreADU does not design, permit or build ADUs.
Read this first
- Bid ≠ survey average ≠ declared valuation ≠ blog $/sf
A contractor’s bid is a price to do named work on a named lot. The CCI 2021 median is what 2018–19 owners said they spent, inclusive of design, labor, materials and permits.
Declared permit valuation is the number on the application, often a city table or an applicant’s guess, used to compute a fee. A blog “ADUs start at $X” is marketing. This page does not collapse the four.
- There is no sticker price, and we will not invent one
Two 800-square-foot detached units on two California lots can differ by a sewer run, a slope, a school-fee threshold, a crane that will not fit, and a finish package.
A statewide average that pretends they do not is the thing we exist not to publish. The cost calculator asks you to type the lines. It ships no national ADU price as a quote.
- This is not a 480-city fee census
A city-by-city fee study of California’s roughly 480 jurisdictions is not on this site. The fee tables below are a sample of published schedules — Los Angeles, San Francisco, San José, Sacramento and Oakland — retrieved on 5 September 2026. They are labeled as a sample. They are not statewide rates.
- Not a quote, and not construction advice
HyreADU does not design, permit or build accessory dwelling units. Nothing here is a bid, an estimate for a specific lot, or legal, tax or financial advice.
Zoning, fee schedules and utility rules are local and they move. The useful next step on a named parcel is the planning counter, a licensed designer, and written bids.
Four numbers that are not the same
Cost pages on the open web treat a survey median, a permit valuation, a city fee table and a contractor’s bid as interchangeable. They are not. Collapsing them is how a $27,000 declared garage conversion becomes a “$250,000 ADU” in a brochure, or the other way around.
- Construction cost (what you spend)
- The cash outlay to a permitted, occupiable unit: design and engineering, site work, foundation, the building, utilities, fees, contingency. Chapple, Ganetsos and Lopez (2021) asked owners for this number and defined it as “the total cost that the homeowner spent on their ADU, and is inclusive of all costs for design, labor, materials, and permits.” It is the only statewide owner-reported construction-cost figure with a method that we retrieved. It is still a 2018–19 survey of people who finished.
- Declared permit valuation
- The dollar amount on the building-permit application. Cities use it to compute plan-check and permit fees; some substitute a published valuation table (Sacramento’s residential new-living-area rate on CDD-0245 is $170.80 per square foot; San José points applicants to ICC construction-tax valuation rates). Applicants under-declare; tables flatten. The five-city distributions below are this number. They are not bids.
- Indexed 2019 dollar (a HyreADU calculation)
- What a published construction-cost index does to a 2019 figure. The California Construction Cost Index is the ENR Building Cost Index averaged for Los Angeles and San Francisco, republished monthly by the Department of General Services. DGS’s own page says it “does not reflect current market bidding environment.” Multiplying the CCI median by the CCCI factor produces an indexed dollar, not a new survey.
- Blog $/sf
- A round number with no vintage, no geography, no sample and no method. “ADUs start at $X” and “California ADUs run $300–$500/sf” circulate without a table we can open. We record that they circulate. We do not ship them as a fact.
The question everybody asks first
“How much does an ADU cost in California?” is the first search, and the category has answered it with a sticker. Builder landers publish a starting price. Realtor roundups publish a per-square-foot band. Calculators pre-fill a rate and call the total “your estimate.”
We went looking for a current, statewide, method-bearing construction-cost survey of California ADU owners. We did not find one dated after April 2021.
What we found is the CCI owner survey of 2018–19 permits and certificates of occupancy, the Terner Center’s 2020 financing brief (which cites a 2020 professional report for an average, not a median), a pair of published construction-cost indexes that can move a 2019 dollar, municipal fee schedules that itemize plan check and impact fees, and five cities’ declared permit valuations.
That is a range with named movers. It is not a price.
HyreADU analysis: a starting price without a vintage, a unit type, a fee regime and a site is a lead magnet. The honest literature is older than the blogs, and older is the finding.
What can be assembled from primary sources is the survey that exists, the index that has moved since then, the valuation that cities actually record, and the fee lines a sample of schedules publish.
A homeowner who needs a number for a specific lot still needs bids.
What Terner and CCI actually published
The Terner Center for Housing Innovation at UC Berkeley, with the Center for Community Innovation, owns the homeowner-facing construction-cost evidence for California ADUs. This page cites that work as theirs. It does not restate it as ours.
Karen Chapple, David Garcia, Eric Valchuis and Julian Tucker, Reaching California’s ADU Potential: Progress to Date and the Need for ADU Finance (Terner Center and Center for Community Innovation, August 2020): “An analysis of ADU construction data suggests that the average ADU cost in California is $167,000, though the cost varies by region and the size/quality of the ADU. In Los Angeles, the average cost estimate is $148,000 while the average cost in the Bay Area is $237,000, a gap that is driven largely by differences in labor costs between the two regions. In fact, ADU construction costs in the Bay Area can exceed $800 per square foot, equaling $400,000 for a 500 square foot ADU.” Footnote 6 of that brief is Eric Valchuis, “HomeOn: Providing Loans to Homeowners to Construct Accessory Dwelling Units,” Master of City Planning professional report, UC Berkeley, 2020.
We retrieved the brief. We did not retrieve the professional report’s underlying table, and we do not invent it.
Karen Chapple, Dori Ganetsos and Emmanuel Lopez, Implementing the Backyard Revolution: Perspectives of California’s ADU Owners (Center for Community Innovation, 22 April 2021) is the survey.
David Garcia and Ben Metcalf of the Terner Center reviewed it; it is CCI’s survey, cited as CCI’s, with Terner in the acknowledgements.
Postcards went in late summer and fall 2020 to 15,745 HCD Annual Progress Report addresses for 2018 or 2019 permits or certificates of occupancy, plus a Bay Area supplement. 823 responses; 4.8 percent after dropping non-owners.
Construction cost “refers to the total cost that the homeowner spent on their ADU, and is inclusive of all costs for design, labor, materials, and permits.”
The survey’s own limitations are the finding’s limitations. Respondents are more affluent than California homeowners (70 percent at $100,000 or more, against 40 percent of Californians in 2019 ACS).
The Bay Area is over-represented (52 percent of respondents); Los Angeles County is under-represented (24 percent of respondents, 54 percent of the postcard population). The sample is people who succeeded. It is not people who got a bid and stopped. It is not 2026.
HyreADU analysis: $150,000 median and $167,000 average are different statistics from different documents.
The regional spread inside the survey — Los Angeles County at $100,000, Bay Area at $177,500 — is larger than the gap between the two statewide headlines.
Type does as much work as region: detached $180,000, garage $90,000. A page that ships one California number has already thrown away the table.
The 2021 owner survey, as published
| Cut | Median total | Median $/sf | What that cut is |
|---|---|---|---|
| Statewide | $150,000 | $250 | n of cost respondents is in Appendix B of the report. Inclusive of design, labor, materials, permits. |
| San Francisco Bay Area | $177,500 | $329.17 | Most expensive region in the survey. 52% of respondents lived here — an over-sample relative to production. |
| Central Coast | $140,000 | $223.04 | Region as defined by the authors. |
| Orange and San Diego Counties | $130,000 | $200.00 | Combined in the report because of sample size. |
| Los Angeles County | $100,000 | $197.22 | Cheapest region in the survey. Authors flag garage conversions as 39% of LA County ADUs in the sample, against 11–14% elsewhere. |
| Detached (new) | $180,000 | $300.00 | 53% of the sample. Most expensive type. |
| Addition to the main residence | $150,000 | $250.00 | 13% of the sample. |
| Garage (conversion or expansion) | $90,000 | $189.19 | 23% of the sample. Cheapest type. May include legalizations of already-converted space; the survey did not ask. |
| Conversion of the main residence | $100,000 | $173.04 | 9% of the sample. Lowest $/sf. |
| Studio | $100,000 | $241.27 | 18% of units were studios. |
| 1-bedroom | $150,000 | $266.67 | 61% of units. |
| 2-bedroom | $212,500 | $250.00 | Most expensive by total. 17% of units. |
| 3 or more bedrooms | $200,000 | $129.17 | 3% of units. Lowest $/sf — kitchens and bathrooms are sunk across more floor area. |
| Owner income under $50,000 | $95,000 | $176.17 | Owners who spent less, not a cheaper market. |
| Owner income $100,000 or more | $170,000 | $306.12 | 70% of respondents. |
Chapple, Ganetsos and Lopez, Implementing the Backyard Revolution, Table 2 and related text, 22 April 2021. Retrieved 2026-09-05. Average ADU in the sample: 615 square feet.
37% of ADUs cost less than $100,000; 71% cost less than $200,000. Those shares are of the 2018–19 survey, not of 2026 production. Financing types in the same table are not mutually exclusive.
What an index does to a 2019 dollar — and what it does not
Construction got more expensive after those owners built. That is not in dispute. How much, for an ADU, is not a number a website is entitled to invent. Two published indexes can be retrieved. Neither is an ADU survey.
California Construction Cost Index (CCCI). The Department of General Services republishes a monthly index “developed based upon Building Cost Index (BCI) cost indices average for San Francisco and Los Angeles ONLY as produced by Engineering News Record (ENR) and reported in the second issue each month.” DGS’s own qualifier, retrieved 2026-09-05: “The ENR BCI reports cost trends for specific construction trade labor and materials in the California market and does not reflect current market bidding environment.” December 2019: 6,924.
August 2026: 10,633. Factor: 1.536. Annual CCCI changes along the way included +13.4% in 2021 and +9.3% in 2022 (December to December), then +2.3% in 2024 and +3.9% in 2025.
Census/HUD constant-quality price index of new single-family houses under construction (Laspeyres, 2005 = 100), from the Survey of Construction. Annual 2019: 134.4. July 2026, preliminary: 199.8. Factor: 1.487. This is a national index of new single-family houses, not of California backyard ADUs.
It is here so a reader can see that the national house-under-construction series moved less, over the same window, than the California ENR-based CCCI — and so that nobody mistakes a national house index for a California ADU price.
ENR 20-city indexes, 17 August 2026 economics tables: Construction Cost Index 14,350.29 (+0.3% month, +3.1% year); Building Cost Index 9,005.51 (+0.5% month, +4.7% year). The 20-city average is not California. CCCI is the California derivative we use for the arithmetic below.
RSMeans city cost books were not accessible on this retrieval (subscription). We do not invent an RSMeans ADU line.
HyreADU calculation — indexation, not a survey. Multiply Chapple et al.’s 2021 medians by the CCCI factor 1.536 (August 2026 / December 2019). Statewide median $150,000 becomes about $230,351 (384/sf). Bay Area $177,500 becomes about $272,582 (505/sf).
Los Angeles County $100,000 becomes about $153,567 (303/sf). Detached $180,000 becomes about $276,421 (461/sf). Garage $90,000 becomes about $138,211 (291/sf). The same exercise on the Census Laspeyres factor 1.487 would put the statewide median at about $222,991.
Two indexes, two indexed dollars, one 2018–19 survey underneath. Neither indexed dollar is a bid, and DGS has already said CCCI is not a bidding environment.
Indexed 2018–19 medians, labeled as indexation
CCCI August 2026 ÷ CCCI December 2019, applied to Chapple, Ganetsos and Lopez Table 2. HyreADU arithmetic. Not a 2026 owner survey.
An index moves every cell by the same factor. It does not know that garage conversions became a smaller share of Los Angeles production, or that a 750-square-foot impact-fee cliff changed the size mix, or that a particular lot needs a new sewer.
Treating the indexed statewide median as “what an ADU costs in 2026” would be the same sin as the sticker. It is a 2018–19 owner median, aged by a labor-and-materials index that DGS itself says is not a bid.
What moves you along the range
The survey already told us type and region do real work. So do the lines a sticker price hides. None of the movers below is a multiplier we will ship as a national index. They are the reasons two lots do not share a price.
Type — the shell you do or do not already have
CCI 2021: detached new construction median $180,000 ($300/sf); garage $90,000 ($189/sf); conversion of the main residence $100,000 ($173/sf); addition $150,000 ($250/sf).
A conversion reuses a roof, walls and a slab; it still pays for insulation, egress, a wet room, electrical and the parking the garage no longer provides.
A detached unit pays for all of those and for a foundation, a new envelope, and a utility run. Prefab moves the factory invoice; it does not erase site work, foundation, crane, or local inspection. The pre-approved-plans directory is about drawings, not about the build.
Region — labor, not a vibe
The 2020 Terner brief attributed the Los Angeles / Bay Area gap “largely” to labor costs.
The 2021 survey found an even larger ADU gap than Terner’s multifamily hard-cost work: Bay Area ADUs $106/sf above the next most expensive region, while Terner’s apartment hard costs in Los Angeles ran $35/sf above the state.
Coastal labor markets and inland labor markets are not one market. CCCI, built from Los Angeles and San Francisco ENR only, cannot speak for Sacramento or Bakersfield.
Declared-valuation medians in the harvests below run from $40,000 in the City of Los Angeles to $156,800 in unincorporated Marin — different cities, different vintages, different valuation practices, not a labor index.
Site and utilities — the lines that do not scale with floor area
A short sewer tie-in and a septic upgrade are not the same project. A flat pad and a hillside retaining wall are not the same project.
A panel with spare capacity and a service upgrade plus a transformer wait are not the same project.
Fourteen percent of CCI 2021 respondents put utility connections among their top challenges; 14 percent put setbacks or height. These lines are why a single $/sf is a lie about the budget.
The cost calculator keeps site work and utilities as their own fields for that reason.
Fees — a cliff at 750 square feet of interior livable space, and a different cliff at 500
Government Code § 66311.5, the current numbering after SB 477 recodified ADU law out of § 65852.2 and SB 543 moved the fee section from § 66324, bars impact fees on an ADU of 750 square feet of interior livable space or less (and on a JADU of 500 or less).
Above 750, impact fees must be proportional to the primary dwelling. School developer fees under Education Code § 17620 are a different statute: § 66311.5(c)(3) treats an ADU or JADU under 500 square feet of interior livable space as not increasing assessable space by 500 square feet.
Connection and capacity charges are not impact fees. A unit at 749 square feet and a unit at 751 square feet can differ by five figures of park, traffic and school charges before anyone lifts a hammer.
Sacramento’s own worksheet, below, shows that cliff in a published municipal estimate.
Who builds it — owner-builder is not a contractor price
Los Angeles’s legacy permit extract is majority owner-builder: 8,312 of 12,627 matched rows, excluded from the contractor harvest under Business and Professions Code § 7044. San Francisco excluded 671 owner-builder permits of 2,005.
An owner-builder’s declared valuation is not a general contractor’s bid, and a contractor-named harvest is not the full market. The valuations below are contractor-named unless noted. They are already the wrong number for a homeowner who intends to be the builder of record.
Finish, wet rooms, and the second bathroom
CCI found two-bedroom units the most expensive by total ($212,500) and three-or-more the cheapest per square foot ($129). Kitchens and bathrooms are sunk costs; a second bath does not scale linearly with floor area.
High-income owners in the survey spent more ($170,000 median) than owners under $50,000 ($95,000). That is finish and size, not a different statute. We have no 2026 finish-tier index and will not invent one.
Declared permit valuation is not construction cost
The distributions in the next table are HyreADU calculations from the five municipal ADU-permit harvests (Los Angeles, San Francisco, Sacramento, San José, unincorporated Marin).
Each nested permit’s valuation field is the city’s recorded declared valuation. Owner-builder-named contractor records are excluded. Zero valuations are dropped.
Per-permit figures are one issued building-permit row; per-site figures sum rows at a distinct site address.
Applicants declare a number to generate a fee. Some cities substitute a published dollar-per-square-foot table. Under-declaration is a known practice; a $20,000 garage-conversion valuation in Los Angeles is not a $20,000 project.
San José’s harvest tops out at $234,848, a tight ceiling that is consistent with a valuation table, not with a market of bids. We publish the distribution because it is what the cities recorded. We do not call it cost.
Declared permit valuation in five harvests
| Jurisdiction | Window (issued) | n (permits > $0) | p25 / median / p75 | Garage median | Non-garage median | What the feed is |
|---|---|---|---|---|---|---|
| City of Los Angeles | 2017-02-28 → 2023-05-19 | 3809 | $20,000 / $40,000 / $81,000 | $27,000 | $80,000 | Legacy LADBS extract (xnhu-aczu). Contractor columns end 19 May 2023; newer LADBS feeds dropped them and are not used. Owner-builder majority excluded. One $17.5 million row remains; it does not move the median. |
| City and County of San Francisco | 2015-06-26 → 2026-08-28 | 1314 | $83,625 / $150,000 / $250,000 | $185,000 | $145,300 | DBI adu = Y, issued only. Contractor license number on the permit. Owner-builder excluded. |
| City of Sacramento | 2018-10-29 → 2026-07-24 | 749 | $85,000 / $133,105 / $195,313 | $80,000 | $150,000 | Building-work activity codes only. City publishes a $170.80/sf new-living-area valuation table (CDD-0245, 12 July 2026). No license number on the permit. |
| City of San José | 2008-02-11 → 2026-08-27 | 459 | $71,819 / $98,971 / $131,648 | $73,800 | $107,023 | City subtype “ADU Accessory Dwelling Unit.” Max in the harvest $234,848. ICC construction-tax valuation rates are on page 25 of the 10 August 2026 fee schedule. No license number on the permit. |
| Marin County (unincorporated) | 2014-04-10 → 2026-07-20 | 277 | $55,000 / $156,800 / $350,000 | $122,500 | $168,000 | Unincorporated county land only — not the ten towns. 145 owner-builder-named permits excluded from this row. Small n; the right tail is long (p90 $659,760). |
HyreADU calculation from harvests generated 29–30 August 2026. Declared permit valuation, not construction cost. Retrieved with the harvests; this page assembled 2026-09-05.
Los Angeles contractor evidence ends 19 May 2023 by construction of the feed, not by choice.
A 2024–26 Los Angeles valuation distribution is not computed here because the current extracts cannot supply the contractor filter this desk uses.
Means are omitted from the headline columns because a single $17.5 million Los Angeles row, and Marin’s long tail, pull them; medians and quartiles are the statistic.
How to read those medians without laundering them into cost
Los Angeles’s contractor-named median of $40,000 sits next to a garage-conversion median of $27,000 (n = 1990) and a non-garage median of $80,000 (n = 1819).
The citywide median is a garage-conversion city showing through the harvest, plus whatever applicants typed to land in a cheap fee bracket.
Chapple et al. already flagged garage conversions as 39 percent of their Los Angeles County sample. CCI’s LA County construction-cost median was $100,000 — two and a half times this harvest’s declared median. That gap is the point. Valuation is not cost.
San Francisco’s median declared valuation of $150,000 (p25 $83,625, p75 $250,000) happens to match the CCI statewide construction-cost median in dollars and not in meaning. SF’s interquartile range runs $83,625 to $250,000.
DBI’s own fee tables (below) charge plan review and issuance on that declared number, which is one reason applicants and departments fight over it.
Sacramento’s median of $133,105 sits close to the city’s published new-living-area valuation rate of $170.80 per square foot times a ~750-square-foot unit ($127,929 on CDD-0419’s own worked example).
When a city publishes the table it will use, declared valuation clusters on the table. San José’s even tighter band (p25 $71,819, median $98,971, p75 $131,648, max $234,848) is the same phenomenon.
Unincorporated Marin’s contractor-named median of $156,800 (n = 277 after dropping 145 owner-builder-named permits) is a small coastal-county sample with a long right tail. It is not “the North Bay.” It is not the ten incorporated towns. It is not a bid.
HyreADU analysis: if declared valuation were construction cost, Los Angeles contractor-named ADUs would be a $40,000 product and San Francisco a $150,000 product, and both would contradict the owner survey, the Terner average, and anyone who has paid a carpenter in either city.
They are fee bases. We report them so a reader who has been shown a permit valuation as “what ADUs cost” can see the distribution and the label.
Fees: a sample of published schedules, not a statewide census
A city-by-city fee study of California’s roughly 480 jurisdictions is not published on this site. Anyone circulating a statewide ADU fee average without a 480-row table is guessing.
What follows is a sample of five published municipal schedules retrieved on 5 September 2026: Los Angeles, San Francisco, San José, Sacramento and Oakland. Where a schedule itemizes plan check, building permit, school, park, traffic or utility, those lines are named. Where it does not, we do not invent them.
Impact fees and school developer fees are different statutes. Connection charges are a third.
Government Code § 66311.5 (added by renumbering § 66324; SB 543, effective 1 January 2026) is the current fee section of State ADU Law.
ADU provisions were recodified out of Government Code § 65852.2 by SB 477 (effective 25 March 2024) into Chapter 13, §§ 66310–66342. We cite the current numbering.
Five published schedules, itemized as far as they go
| City (schedule retrieved) | Plan check / building permit | School | Park / traffic / other impact | Utility connection / capacity | A worked figure the schedule actually publishes |
|---|---|---|---|---|---|
| City of Los Angeles — LAMC Table 1-A (Housing Element Appendix 2.4, table effective 16 July 2018); plan check LAMC 91.107.3.1.1; ZA Memo 143 Rev. 1 (1 August 2025) | Building permit is a sliding valuation table (Table 1-A). Plan check equals 90% of the building-permit fee. LADBS CPI-adjusts; the 2018 table is the published structure, not a 2026 dollar quote. | School developer fees are LAUSD’s, not LADBS’s. ADUs under 500 sf of interior livable space are treated, under Gov. Code § 66311.5(c)(3), as not increasing assessable space by 500 sf for Education Code § 17620. Above that, the district’s residential rate applies. We did not retrieve a 5 September 2026 LAUSD board sheet; Sacramento’s 1 September 2026 district roster lists the State Allocation Board Level 1 residential rate at $5.38/sf for several districts. | ZA Memo 143: ADUs and JADUs are exempt from Park Fees (LAMC 12.33) and the Affordable Housing Linkage Fee (LAMC 19.18). Residential Development Fee (LAMC 21.13.3) and Dwelling Unit Construction Tax (LAMC 21.10.3) are named as impact-fee-affected. Units ≤ 750 sf interior livable are barred from impact fees by § 66311.5. | Connection and capacity charges are not impact fees. DWP water and power, and Bureau of Sanitation sewer capacity, are separate bills. § 66311.5(b): an ADU is not a new residential use for connection-fee purposes unless built with a new single-family dwelling. | No current LADBS ADU fee worksheet comparable to Sacramento’s CDD-0419 was retrieved. We will not invent a “typical LA ADU permit total.” |
| San Francisco — DBI Table 1A-A, fees on and after 12 July 2026 (Ord. 112-26) | Two charges: plan review and permit issuance, both from total valuation. $50,001–$200,000 band: plan review $1,617 for the first $50,000 plus $15.60 per additional $1,000; issuance $677 plus $4.83 per additional $1,000. Note 1: these fees do not include Public Works, Planning, Fire, Public Health, or plumbing/electrical/mechanical permit fees. | SFUSD school facility fees are calculated by DBI staff, not printed as a single ADU line on Table 1A-A. Under 500 sf interior livable, § 66311.5(c)(3) applies. | Impact fees on ADUs ≤ 750 sf interior livable are barred statewide. San Francisco’s remaining impact-fee treatment of larger ADUs is not itemized on Table 1A-A. | SFPUC water/sewer and Public Works right-of-way permits sit outside Table 1A-A. Separate plumbing (Table 1A-C) and electrical (Table 1A-E) permits apply. | HyreADU arithmetic on Table 1A-A, not a DBI quote: a $150,000 declared valuation (the SF harvest median) lands in the $50k–$200k band. Plan review $1,617 + ($15.60 × 100) = $3,177. Issuance $677 + ($4.83 × 100) = $1,160. Building-permit subtotal $4,337, before Planning, trades, school or utilities. |
| San José — Building Division fee schedule effective 10 August 2026; ADU fees page | ADU-specific, by floor area, not by valuation. 0–750 sf: permit issuance $422, plan review $1,137, inspection $1,732 (issuance includes addressing; inspection includes meter release). 751–1,200 sf: $633 / $1,950 / $2,520. Modular: 10% lower plan review, 20% lower inspection. Hourly floors: plan review $325/hr, inspection $315/hr, if greater. | School impact fees “do not apply to ADUs less than 750 sq. ft.” (city ADU fees page, retrieved 5 September 2026). At 750 sf or greater, contact the school district. The city’s 750 sf phrasing is the impact-fee threshold; school fees also have the 500 sf Education Code test in state law. | Parkland impact fees: same city page, “do not apply to ADUs less than 750 sq. ft.” At 750 or greater, parkland fees vary by MLS location (Park Impact In-Lieu Fee schedule). | Public Works and utility-permit schedules are separate (PW fees effective 10 August 2026; utility permits 1 September 2026). Not folded into the Building Division ADU line. | Building Division only, HyreADU addition of the published cells: 0–750 sf ADU = $422 + $1,137 + $1,732 = $3,291. 751–1,200 sf = $633 + $1,950 + $2,520 = $5,103. School and parkland extra at the 750 sf threshold; not in those totals. |
| Sacramento — CDD-0419 ADU Fee Estimate (new construction), revised 12 July 2026; CDD-0245 residential fee table; CDD-0226 school districts, revised 1 September 2026 | Valuation-based. City valuation table (CDD-0245): new living area $170.80/sf; garage conversion $101.16/sf. Building permit and plan review from the valuation table (plan review 42% of permit above $100,000). Fire admin $176; fire inspection $0.11/sf (min $294); fire plan review $260; planning inspection $526; planning review $263. | Paid at the school district, proof required before issuance. CDD-0226 (1 September 2026): Sacramento City Unified $5.38/sf residential; San Juan Unified $5.38; Elk Grove Unified $7.23. Not in the CDD-0419 total. | Park Development Impact Fee, SAFCA DIF, and Sacramento Transportation Authority mitigation (plus 2% admin) are $0 on the 749 sf column and live on the 750 sf and 1,200 sf columns. That is the 750 sf cliff in a city worksheet. | Utilities fee $205 deposit + hourly. Regional sanitation and city sewer development: “Check with County.” ADUs “generally connect to existing sewer lines or tie into the line of the main dwelling unit.” Water development may be waived in designated infill; ADUs generally do not require a separate meter. | CDD-0419’s own columns, excluding school: 749 sf (valuation $127,929.20) total about $5,271.90. 750 sf (valuation $128,100) about $10,624.40. 1,200 sf (valuation $204,960) about $14,842.50. One square foot more than 749 adds park $2,617.50 + SAFCA $1,575 + STA $1,154.64, which is why the 750 sf total roughly doubles. |
| Oakland — Impact Fee Amounts page; Impact Fee Assessment and Appeal Information (Ord. 13853, effective 13 September 2025); Master Fee Schedule FY 2026–27 | Building permit fees: the city’s own Impact Fees page says they are “usually 4–6% of project value,” with details at the Building Permit Counter. That is the city’s description, not a HyreADU calculation, and not an ADU-specific table. | School fees collected by Planning and Building on behalf of OUSD. The Impact Fee Amounts page retrieved 5 September 2026 still lists residential $5.17/sf (commercial $0.84/sf). Several other California districts on Sacramento’s 1 September roster have moved to the $5.38 Level 1 rate. We report what Oakland’s page said on retrieval, and we do not silently update it. | ADUs are listed as exempt from Affordable Housing, Transportation, and Capital Improvements impact fees under the 13 September 2025 rules. The exemption is the city’s, in addition to the statewide 750 sf bar. | EBMUD water service and private sewer lateral rules sit outside the city impact-fee manual. Not priced here. | No Oakland ADU fee worksheet with a bottom-line total was retrieved. The finding from this schedule is the exemption, not a dollar. |
Sample of published municipal schedules, not a statewide fee census. Retrieved 2026-09-05.
A sixth, seventh or 480th city would change a statewide average. There is no statewide average on this page because there is no 480-row table. Worked figures that are HyreADU arithmetic from a published cell are labeled as such. CDD-0419’s column totals are the city’s.
The 750-square-foot cliff, in the current statute
State ADU Law no longer lives at Government Code § 65852.2. SB 477 (Stats. 2024, Ch. 7, effective 25 March 2024) recodified it into Chapter 13 of Division 1 of Title 7, §§ 66310–66342.
The fee rules that used to sit in former § 65852.2, and then at § 66324, were renumbered to § 66311.5 by SB 543 (Stats. 2025, Ch. 520, effective 1 January 2026). The current text, retrieved 5 September 2026:
“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. 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.” “Impact fee” takes the Mitigation Fee Act definition in § 66000(b) and also includes park fees under § 66477. It “does not include any connection fee or capacity charge.”
Interior livable space is the measurement SB 543 wrote in. A page that still cites § 65852.2 for this rule is citing a repealed numbering. A page that treats school fees, park fees and sewer capacity as one “impact fee” is collapsing three statutes.
Sacramento CDD-0419 is the rare schedule that prints the cliff as three columns. At 749 square feet the city estimates about $5,272, with park, SAFCA and STA at zero.
At 750 square feet the same worksheet estimates about $10,624, before school. That is not a HyreADU finding about every California city. It is one city’s published illustration of the statute it has to administer.
HyreADU analysis: size is a cost decision and a fee decision, and they part at 750 square feet of interior livable space (and, for school fees, at 500).
A unit drawn at 749 to stay under the impact-fee bar is a documented pattern, not a trick we will moralise about.
A unit drawn at 800 because a household needs two bedrooms is a different project with a different fee stack. The range moves when you cross the line. The calculator will not cross it for you.
The lines a sticker price hides
Usually in the “building” number
Foundation, framing, envelope, windows, insulation, drywall, finish, kitchen, bathroom, electrical, plumbing, mechanical, Title 24, solar on new construction. This is the line people mean by $/sf.
CCI’s $250/sf and $300/sf detached are this line plus design and permits, in 2018–19 dollars, from owners who finished. A bid that is “$280/sf, allowances to be determined” has not priced this line. It has priced a hope.
Usually not
Survey, soils, design revisions, plan-check resubmittals, school and park at the 750 sf line, sewer capacity, water meter or lateral, electrical service upgrade, tree protection, demolition, haul-off, temporary power, crane, driveway replacement, landscaping the city now requires, and the contingency the owner holds.
CCI respondents who cited “$45,000 just for permits” and dropped out are in the 2022 Terner/CCI focus groups, not in the 2021 cost median — because the median is people who built.
What a homeowner can actually do with this
Type the lines you have into the ADU cost calculator. Leave the building rate at $0 until a designer or a bid gives you one. A $0 building line is more honest than a fake $300/sf. Site work and utilities stay separate because they do not scale with floor area.
Ask planning for the fee schedule that applies to a new dwelling unit on this parcel, and ask whether the unit as drawn is at, under, or over 750 square feet of interior livable space. Sacramento’s worksheet is a model of the question. A verbal “permits are about ten thousand” is not.
Do not take a declared permit valuation, from this page or from a neighbor’s job card, as the construction budget. Los Angeles contractor-named medians in the harvest are $40,000. CCI’s Los Angeles County owners reported $100,000. Both can be true.
Do not take the indexed $150,000 — about $230,351 in August 2026 CCCI dollars — as a quote. It is a 2018–19 owner median aged by a labor-and-materials index that is not a bid. If the project only works at a blog starting price, it does not work on the evidence this page could find.
If the question is how the money is raised, that is the financing-landscape study.
If the question is what the unit is worth on resale, that is the appraisal study — and cost is not value.
If the question is rent, that is the rental-income study, with the CCI finding that a large share of units are not let at market.
HyreADU analysis: the category has been answering a budget question with a sticker because a range does not close a lead. A range is still the evidence. We would rather publish the longer honest page than a price we cannot source.
Method
- Primary sources, retrieved 5 September 2026
Chapple, Garcia, Valchuis and Tucker, Reaching California’s ADU Potential (August 2020), including footnote 6 (Valchuis 2020 MCP professional report). Chapple, Ganetsos and Lopez, Implementing the Backyard Revolution (22 April 2021), Table 2 and methodology appendix.
Greenberg, Phalen, Chapple, Garcia and Alameldin, ADUs for All (August 2022), for the “$45,000 just for permits” quotation and the restated $150,000 median. DGS CCCI tables (December 2019 = 6,924; August 2026 = 10,633).
Census/HUD houses-under-construction Laspeyres index (annual 2019 = 134.4; July 2026 preliminary = 199.8). ENR 20-city CCI/BCI, 17 August 2026 PDF. Government Code § 66311.5. Fee schedules named in the source list. Five permit harvests generated 29–30 August 2026.
- Terner is cited as Terner; CCI as CCI
The 2020 average ($167,000) is Terner/CCI citing Valchuis. The 2021 median ($150,000) is CCI, reviewed by Terner. We do not collapse them, and we do not restated either as a HyreADU survey.
- Indexation is labeled as a HyreADU calculation
CCCI factor 1.536 = 10,633 / 6,924. Applied cell-wise to Table 2 of Chapple et al. 2021. Rounded to the nearest dollar in the helper JSON. DGS’s bidding-environment disclaimer travels with the number.
- Declared valuation is labeled as declared valuation
Helper JSON at src/data/research/adu-cost-california-valuations.json. Nested permit.valuation; owner-builder-named records excluded; zeros dropped; quartiles are linear interpolation on the sorted list. Los Angeles contractor columns end 19 May 2023.
- Fees are a sample
Five cities. Not 480. Worked arithmetic from a published cell is labeled as HyreADU arithmetic. CDD-0419 column totals are Sacramento’s. No statewide fee average is computed because the inputs will not support one.
- What we searched for and did not use
RSMeans city books (subscription, not retrieved). A post-2021 statewide ADU owner cost survey (not found). A 480-jurisdiction fee census (not on this site). Builder and realtor “starting at” prices (recorded as circulation, not as evidence).
Limitations, again, because they are the finding
- The cost survey is five years old, and five years is not a rounding error
2018–19 permits, surveyed in 2020, published April 2021. CCCI moved by half. An index is not a re-survey of owners, and the owners who answer surveys are not the owners who never start.
A 2026 statewide owner survey would supersede the median; it would not supersede the warning that type, region, site, utilities and the 750 sf line move the range.
- Los Angeles contractor valuations stop in May 2023
The legacy extract is the only LADBS shape that carries contractor of record. Using the current extracts would mix a different population into a contractor-named statistic. We stop where the column stops.
- Five fee schedules are five fee schedules
Sacramento’s 749/750 cliff is Sacramento’s. San José’s ADU-specific Building Division cells are San José’s. Oakland’s impact-fee exemption is Oakland’s. A sixth city can look nothing like these five. That is why there is no statewide fee average here.
- CCCI is not a bid, in DGS’s own words
Labor and materials in Los Angeles and San Francisco, from ENR, not a contractor’s price on your lot, not Sacramento, not a garage conversion, not a prefab invoice.
- It is not a recommendation
A legal ADU can house a person, collect a rent, or do neither.
Whether a particular lot can carry a particular invoice is a bid and a fee quote, not a research page. This page describes the range and the movers.
It does not tell you to build, and it does not tell you not to.
Questions
How much does an ADU cost in California?
What is a typical ADU cost per square foot?
Do ADUs start at $100,000?
Is declared permit valuation the same as construction cost?
How much are ADU permit fees in California?
Are ADUs under 750 square feet exempt from fees?
Did the Terner Center say ADUs cost $150,000?
Has construction inflation made those survey numbers obsolete?
Is a garage conversion cheaper than a detached ADU?
Is this a quote?
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 Terner/CCI papers, DGS CCCI, Census construction price index, ENR 20-city indexes, and municipal fee schedules retrieved 2026-09-05; permit harvests generated 29–30 August 2026. 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
- Karen Chapple, Dori Ganetsos and Emmanuel Lopez, Implementing the Backyard Revolution: Perspectives of California’s ADU Owners (UC Berkeley Center for Community Innovation, 22 April 2021) , Statewide owner survey of 2018–19 HCD APR addresses. Median construction cost $150,000 / $250/sf, inclusive of design, labor, materials and permits. Table 2 regional and type cuts. 37% under $100,000; 71% under $200,000. Average size 615 sf. Terner staff reviewed; cited as CCI’s. Retrieved 2026-09-05.
- Karen Chapple, David Garcia, Eric Valchuis and Julian Tucker, Reaching California’s ADU Potential: Progress to Date and the Need for ADU Finance (Terner Center and Center for Community Innovation, August 2020) , Average ADU cost $167,000; Los Angeles $148,000; Bay Area $237,000; Bay Area can exceed $800/sf. Footnote 6: Valchuis, “HomeOn,” MCP professional report, UC Berkeley, 2020. Cited as Terner/CCI’s. Average, not median. Retrieved 2026-09-05.
- Terner Center, “First Ever Statewide ADU Owner Survey Shows Growth, Room for Improvement” (22 April 2021) , Terner’s own digest of the CCI survey, including the $150,000 / $250/sf median. Cited so the attribution trail is visible. Retrieved 2026-09-05.
- Julia Greenberg, Hannah Phalen, Karen Chapple, David Garcia and Muhammad Alameldin, ADUs for All (Terner Center and Center for Community Innovation, August 2022) , Focus groups: cost the most prevalent challenge; restates the 2021 $150,000 / $250/sf median; “I needed to come up with $45,000 just for permits, and I couldn’t get that.” Retrieved 2026-09-05.
- California Department of General Services — California Construction Cost Index (CCCI) , ENR Building Cost Index averaged for San Francisco and Los Angeles only. December 2019 = 6,924; August 2026 = 10,633. DGS: “does not reflect current market bidding environment.” Annual % December-to-December: 2021 +13.4%, 2022 +9.3%, 2023 +9.4%, 2024 +2.3%, 2025 +3.9%. Retrieved 2026-09-05.
- U.S. Census Bureau and HUD — Price Indexes of New Single-Family Houses Under Construction (Laspeyres, 2005 = 100) , Survey of Construction. Annual 2019 = 134.4; July 2026 preliminary = 199.8. National, not California, not ADU-specific. xlsx current series, last revised 25 August 2026. Retrieved 2026-09-05.
- Engineering News-Record, Construction Economics, 17 August 2026 (20-city averages) , Construction Cost Index 14,350.29 (+0.3% month, +3.1% year). Building Cost Index 9,005.51 (+0.5% month, +4.7% year). 20-city average; CCCI is the California (LA + SF) BCI derivative. Retrieved 2026-09-05.
- California Government Code § 66311.5 , Current ADU/JADU fee section (added by renumbering § 66324; SB 543, Stats. 2025, Ch. 520, effective 1 January 2026). Impact fees barred at 750 sf interior livable or less (JADU 500 or less); above 750, proportional to the primary dwelling. Connection/capacity charges excluded from “impact fee.” School-fee treatment under 500 sf in (c)(3). ADU law recodified out of § 65852.2 by SB 477 (March 2024). Retrieved 2026-09-05.
- San Francisco Department of Building Inspection — Table 1A-A, Building Permit Fees (on and after 12 July 2026) , Plan review and permit issuance by total valuation. $50,001–$200,000: plan review $1,617 + $15.60 per additional $1,000; issuance $677 + $4.83 per additional $1,000. Note 1 excludes other departments and trade permits. Fees on and after 12 July 2026. Retrieved 2026-09-05.
- City of San José — Building and Structure Permits Fee Schedule, effective 10 August 2026 , ADU new/alteration: 0–750 sf issuance $422, plan review $1,137, inspection $1,732; 751–1,200 sf $633 / $1,950 / $2,520. ICC construction-tax valuation rates on page 25, effective 1 July 2026. Retrieved 2026-09-05.
- City of San José — Fees for ADUs , School and parkland impact fees “do not apply to ADUs less than 750 sq. ft.” as of 1 January 2020, per the city page. Not a 480-city statement. Retrieved 2026-09-05.
- City of Sacramento — CDD-0419 Accessory Dwelling Unit (ADU) Fee Estimate (New Construction), revised 12 July 2026 , Worked columns at 749 / 750 / 1,200 sf. Totals about $5,271.90 / $10,624.40 / $14,842.50 excluding school. Park, SAFCA and STA are zero at 749 sf and live at 750 sf. Valuation $170.80/sf. Retrieved 2026-09-05.
- City of Sacramento — CDD-0245 Fees and Charges on Residential Building Permits, revised 12 July 2026 , Residential valuation table: new living area $170.80/sf; garage conversion $101.16/sf. Building-permit and plan-review schedule by valuation. Retrieved 2026-09-05.
- City of Sacramento — CDD-0226 School District Impact Fees, revised 1 September 2026 , Sacramento City Unified $5.38/sf residential; San Juan Unified $5.38; Elk Grove Unified $7.23. Paid at the district; proof required before city issuance. Retrieved 2026-09-05.
- City of Los Angeles — Housing Element 2021–2029 Appendix 2.4, LAMC Table 1-A building-permit fees , Table effective 16 July 2018 (Ord. 185,587). Sliding valuation brackets; plan check equal to 90% of the building-permit fee (LAMC 91.107.3.1.1). Structure of the LADBS fee, not a 2026 dollar quote. Retrieved 2026-09-05.
- Los Angeles Department of City Planning — ZA Memo 143, Revision 1 (1 August 2025) , Correlates ADU rules to the SB 477 numbering (§§ 66310–66342). ADUs/JADUs exempt from Park Fees (LAMC 12.33) and Affordable Housing Linkage Fee (LAMC 19.18). Impact-fee discussion of Residential Development Fee and Dwelling Unit Construction Tax. Retrieved 2026-09-05.
- City of Oakland — Impact Fee Amounts; Impact Fee Assessment and Appeal Information (Ord. 13853, effective 13 September 2025) , ADUs listed as exempt from Affordable Housing, Transportation and Capital Improvements impact fees. School fees on the Amounts page: residential $5.17/sf as retrieved. Building permits “usually 4–6% of project value” is the city’s description. Retrieved 2026-09-05.
- HyreADU permit harvests — ca-la, ca-sf, ca-sacramento, ca-sanjose, ca-marin adu-permits.json , Generated 29–30 August 2026 from municipal open data. Nested permit.valuation distributions computed 2026-09-05; helper JSON at src/data/research/adu-cost-california-valuations.json. Declared permit valuation, not construction cost. Los Angeles contractor columns end 19 May 2023. Owner-builder-named records excluded. Retrieved 2026-08-29.
A range is not a quote. Type the lines you actually have.
Design, permits, site, utilities, a building rate from a bid, a contingency you hold. The calculator will not fill a national ADU price. Empty lines stay $0. That is the honest total.
HyreADU does not design, permit or build accessory dwelling units, and does not appraise, assess, lend, invest or prepare taxes. This page is informational. It is not a quote, a bid, or financial, tax, legal, insurance or construction advice.
Construction-cost figures from the Terner Center and the Center for Community Innovation are cited as theirs and are 2020–21 vintage; indexation of those figures by the California Construction Cost Index is a HyreADU calculation, not a 2026 owner survey, and DGS states that CCCI does not reflect the current market bidding environment.
Declared permit valuation is not construction cost. Fee tables are a sample of published schedules retrieved on 5 September 2026, not a census of California’s roughly 480 jurisdictions. A city-by-city fee study is not on this site.
Government Code ADU fee rules were retrieved at § 66311.5; older citations to § 65852.2 are a repealed numbering.