Junior ADU (JADU) · checked Oct 18, 2026
Junior ADU fees in Milpitas: $4,757–$5,460 for a 500 sq ft JADU
A junior ADU of up to 500 sq ft inside the house pays no impact fees, no school fees and no new utility connection charge under state law. What’s left in Milpitas is permit and review work: building permit & plan check $4,757–$5,460.
Milpitas’s schedule
What Milpitas’s documents say about junior ADUs
- New address request permit
A separate address is required for a new ADU or JADU. The new address request permit
We model a junior ADU as a conversion of space inside the home, using the same schedule lines as an ADU. Where the City charges a JADU less, that’s noted above.
Line by line: junior ADU vs new detached ADU at 500 sq ft
Law in force today. The detached column is for comparison only.
| Fee | Junior ADU, 500 sq ft | New detached ADU, 500 sq ft |
|---|---|---|
| Building permit & plan check | ||
| Building, planning and land development permit fees (City estimate table) | Est.$4,048 | Est.$4,048 |
| New address request permit | $709 | $709 |
| Fire sprinkler review | May apply$703 | May apply$703 |
| Impact fees | ||
| Park in-lieu fee | Exempt | Exempt |
| School district fee | ||
| School fee (statewide cap shown) | Exempt | Exempt |
| Utility connections | ||
| Water connection fee | Exempt | May apply$478 |
| Sewer connection fee | Exempt | May apply$477 |
| Treatment plant fee (new sewer connection) | Exempt | May apply$220 |
| Modeled total | $4,757–$5,460 | $4,757–$6,635 |
State law
The rules for a junior ADU
One per single-family lot, inside the house (an attached garage counts), up to 500 sq ft with an efficiency kitchen. No extra parking; owner occupancy only if it shares a bathroom.
Gov. Code §66313(d)
“Junior accessory dwelling unit” means a unit that is no more than 500 square feet of interior livable space in size and contained entirely within a single-family residence.
Gov. Code §66333(a)
Limit the number of junior accessory dwelling units to one per residential lot zoned for single-family residences with a single-family residence built, or proposed to be built, on the lot.
Gov. Code §66333(d)
For purposes of this subdivision, enclosed uses within the residence, such as attached garages, are considered a part of the proposed or existing single-family residence.
Gov. Code §66333(f)
Require the permitted junior accessory dwelling unit to include an efficiency kitchen
Gov. Code §66334(a)
A junior accessory dwelling unit ordinance adopted pursuant to Section 66333 shall not require additional parking as a condition to grant a permit.
Gov. Code §66333(b)
Owner-occupancy shall not be required if the junior accessory dwelling unit has separate sanitation facilities, or if the owner is another governmental agency, land trust, or housing organization.
Quoted from Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab), checked Oct 18, 2026.
FAQ
Questions about junior ADUs in Milpitas
How much are junior ADU fees in Milpitas?
Our model of Milpitas’s official schedules comes to $4,757–$5,460 for a 500 sq ft junior ADU, compared with $4,757–$6,635 for a new detached ADU of the same size.
Do junior ADUs pay impact or school fees?
No. State law bars impact fees on a junior ADU of 500 sq ft or less (Gov. Code §66311.5(c)(1)), and school fees apply only when a project adds more than 500 sq ft of assessable space (Ed. Code §17620; Gov. Code §66311.5(c)(3)).
Can I build a junior ADU and an ADU on the same lot?
Yes. On a single-family lot, state law requires cities to approve one ADU and one junior ADU, plus a detached ADU of up to 800 sq ft (Gov. Code §66323(a)).
Do I have to live on the property?
Only if the junior ADU shares a bathroom with the main house. With its own bathroom, no owner-occupancy rule applies (Gov. Code §66333(b)).
Not modeled yet
What these totals leave out
- The City's estimate table is based on the FY 2025-26 schedule and is labeled a minimum; Milpitas adopted a new user and regulatory fee schedule effective November 2, 2026 that we haven't modeled line by line yet.
- ADUs in the Milpitas Metro (TASP) area may owe the area's development impact fee ($51,828 per residential unit in FY 2026-27); whether and how it applies to an ADU isn't stated, so it isn't included.
- School district rate not captured; shown at the statewide cap.
- Local size, height and parking rules not captured yet; the state minimums apply.
More
Keep going
Sources
Official sources
Every figure comes from these documents; each line’s quoted text is on the Milpitas page.
- City of Milpitas, Office of Building SafetyAccessory Dwelling Unit (ADU) Permit Fee Estimate (handout dated June 11, 2026; based on the FY 2025-26 fee schedule) (opens in new tab)
- City of MilpitasFY 26-27 Planning Permit Fees and Development Impact Fees (approved June 2, 2026, effective August 3, 2026) (opens in new tab)
- California State Allocation Board (Department of General Services, OPSC)State Allocation Board item: 2026 adjustment to the Level I developer fee (meeting of January 28, 2026) (opens in new tab)
- California Legislative Information (leginfo.legislature.ca.gov)Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab)
- HCD via data.ca.govHousing Element Annual Progress Report (APR) data, Table A2: ADU building permits by year (opens in new tab)