Two numbers, kept apart. City fees come from the city's own fee pages. The build price is our estimate from the last owner survey and today's published prices. How we got it
Official City fees
Line by line
The city doesn't publish a total for an ADU, so we list each charge.See every fee [1][2]
All in, before school and utility fees: about $350k to $465k for a 750 sq ft detached ADU. Adjust it for your lot
10 licensed builders list Fremont on their own sites. Your quote request goes to the Bay Area ADU Builders team.
Get 3 quotes10 licensed builders list Fremont on their own sites. Three quotes for your lot show where in the range you land. Your request goes to the Bay Area ADU Builders team.
Get 3 quotesChange the type and size. City fees come from Fremont's own averages; the building cost is our estimate.
Building (middle) City fees School fees Parkland
Not included: water and sewer connection, and site surprises like a long utility run or a crane. See the fee list below.
Get 3 quotes to check this numberThe top three by our public score for Fremont. Some publish prices, which is the quickest check on the estimate above.
Based in Pleasanton, Alameda County
CSLB #1094866 active Class B Licensed 4 years
Based in Campbell, Santa Clara County
CSLB #638333 active Class B Licensed 34 years
Based in Santa Clara, Santa Clara County
CSLB #889458 active Class B Licensed 19 years
| Building plan check and inspection (valuation table) | $967.27 for the first $100,000 of valuation, plus $5.91 per extra $1,000 up to $500,000[1][7] Minimum valuation for a new wood-frame home (R-3, type VB) is $210.01 per sq ft. Add a $153 application fee, a 15% community planning fee and a 3% technology fee. Trade plan check on new construction is 25% of building plan check, $292 minimum per trade. |
|---|---|
| Ministerial design review (ADU/JADU, new) | $2,000 deposit, billed at cost[1] |
| Plan review with a preapproved plan | $1,000 flat[8] Construction and inspection fees still apply. |
| New address | $278[1][2] Every ADU and JADU needs its own address. |
| Construction tax | $3,137 per new single-family dwelling unit[1] The schedule has no ADU line. Ask the city whether it applies to your ADU. |
| City impact fees | $0 at any size[2][9] Fremont says ADUs are not subject to its development impact fees, regardless of size. |
| School fees (Fremont Unified) | $5.38 per sq ft over 500 sq ft[10] ADUs of 500 sq ft or less pay nothing. Above that, the whole square footage is charged. |
| Sewer capacity charge (Union Sanitary District) | $6.46 per sq ft from Oct 1, 2026[11][12] Applies to detached ADUs and additions over 150 sq ft; none for an ADU inside existing living space. USD says this is not an impact fee, so the state exemption under 750 sq ft does not apply. It rises each year to $7.18 per sq ft in FY2032. |
| Water connection (Alameda County Water District) | $11,093 per single-family dwelling unit[13][14] ACWD's schedule has no ADU line. State law says utility charges for an ADU must be in proportion to its size or plumbing fixtures, and an ADU inside existing space pays none. |
The last survey of what Bay Area owners actually paid is from UC Berkeley in 2021: a median of $329 per sq ft for ADUs permitted in 2018 and 2019.[3] Construction prices in California have risen about 60% since then by the state's own cost index (2018-2019 average 6,719 to September 2026: 10,717).[4] We check that against two current numbers and use the spread as the range.
Smaller units cost more per foot. We scale by size the way Abodu's own price list does. The survey counted design and permits in its figure, so a little of the city fee may overlap.
Abodu published all-in prices (home + typical installation).[6]
Not included: Survey package ($6,000), trenching past 50 ft, crane past 100 ft, demolition, site engineering and sales tax.
None of these pages cites where its number comes from.
For a 750 sq ft detached ADU, our estimate is $350,000 to $465,000 to build. School and utility fees can add more.[1][2][3][4][5]
The city doesn't publish a total. No published total; see fee lines The fee lines on this page list each charge.[1][2]
No. State law bars impact fees on ADUs under 750 sq ft. Larger ADUs pay in proportion to the main home. School fees follow a different rule, and districts disagree about it, so ask yours.[14]
Every fact on this page links to one of these. We read each one on the date shown.