Milpitas / ADU construction
ADU Construction in Milpitas
Milpitas allows an attached ADU, a detached ADU and a junior ADU on one lot.
Milpitas's updated zoning code allows up to three units on a single-family lot, and the city runs a pre-approved plan program with a 30 day review. We design and build ADUs here, starting with the two questions that decide the path: is the lot in a flood zone, and is it in the hillside area.
TWO WAYS TO PERMIT
Pre-approved plan or custom design.
Milpitas launched its pre-approved detached ADU program in 2024. It trades design freedom for a shorter review, and some lots cannot use it at all.
| Pre-approved plan | Custom design | |
|---|---|---|
| City review deadline | 30 days from a complete application | 60 days from a complete application |
| Plan review fee | Billed hourly, lower than full plan review | Standard fee schedule |
| Sizes | Seven plans, 499 to 1,000 sq ft | Up to 1,200 sq ft detached |
| Changes to the plan | Not allowed | Designed to the site |
| Hillside Building Code area | Not eligible | Allowed, with hillside review |
| FEMA flood zones A, AE, AH, AO | Only with a flood-resistant plan option | Allowed, built to flood rules |
Source: Milpitas Pre-Approved ADU Program and Zoning Code C.10.030 ↗
WHAT MILPITAS ALLOWS
Up to three units behind one house.
On a single-family lot, Milpitas zoning section C.10.030 allows one attached ADU, one detached ADU and one junior ADU. A detached ADU can reach 1,200 square feet, and an ADU that meets the city's standards needs only a building permit, reviewed within 60 days, or 30 days with a pre-approved plan.
Detached ADU
Up to 1,200 square feet and 16 feet high, or 18 feet near major transit, with 4 foot side and rear setbacks and an 8 foot front setback.
Attached ADU
Up to 50 percent of the main home, never limited below 800 square feet, and up to 25 feet high. No interior connection to the main house.
Garage conversion
Existing space can exceed the size limits, the lost parking is not replaced, and the garage door is swapped for windows or a door matching the house.
Junior ADU
Up to 500 square feet inside the home with its own entrance. The owner must live on site, recorded with a deed restriction.
Pre-approved plans
Seven city-approved plans from 499 to 1,000 square feet. Plans over 800 square feet also need a Minor Site Development Permit.
Multifamily lots
Up to 8 detached ADUs on a lot with an existing multifamily building, plus conversions of up to 25 percent of the existing units.
MILPITAS AT A GLANCE
Who handles a Milpitas ADU.
Planning sets the ADU rules, the Office of Building Safety issues the permit, Land Development checks flood zones and utility connections, and PG&E sets the meter. Milpitas offers free ADU Monday consultations with all three city teams.
- 1,200
- sq ft maximum for a detached ADU
- 30
- days for review with a pre-approved plan, 60 otherwise
- 40%
- of Milpitas homes built before 1980
Planning
Planning Department
Answers questions on the ADU and JADU rules in zoning section C.10.030 and on Minor Site Development Permits. Free virtual ADU Monday appointments can be booked online, or email adu@milpitas.gov.
(408) 586-3279Milpitas ADU page ↗Permits
Office of Building Safety
ADU building permits are submitted online and tracked in eTRAKiT. Inspections are booked online or on the 24-hour line at (408) 586-2797.
(408) 586-3240Pre-Approved ADU Program ↗Milpitas fee schedules ↗Flood zones
Land Development Engineering
About a quarter of Milpitas is in FEMA's Special Flood Hazard Area. Engineering confirms flood zone status, development requirements and whether the city has an elevation certificate on file.
(408) 586-3329Know your hazard ↗WHAT SLOWS ADUS IN MILPITAS
Problems Milpitas owners run into, and how we plan around them.
From the city's ADU pages, its pre-approved plan rules and its flood hazard information. Most delays start with the lot, not the building.
The lot turns out to be in a FEMA flood zone.
About a quarter of Milpitas lies in the Special Flood Hazard Area, so the parcel's flood zone is checked on the city's map before a plan is chosen.
The house is east of Park Victoria, and the pre-approved plan is off the table.
Parcels in the Hillside Building Code area are screened at the first visit and go straight to a custom design path.
A pre-approved plan needs one small change.
Any modification disqualifies the plan, so site fit is confirmed first, and a custom design is drawn when it does not fit.
The detached ADU lands on an easement.
The city bars detached ADUs from easements, so the title report and site plan are reviewed before layout.
Neighbors object to windows facing their yard.
The city requires a 6 foot fence or screening plants with a mature height of 10 feet when an ADU is closer than 10 feet to a side or rear line, so screening is part of the design.
Sources: milpitas.gov Pre-Approved ADU Program, ADU pages, City Flood Advisory Brochure and Zoning Code C.10.030.
Planning the work
How a Milpitas ADU gets built.
Site check
Free visit. Flood zone, hillside area, easements, utilities and whether a pre-approved plan fits.
Design and city meeting
Plans drawn or a pre-approved plan adapted, with a free ADU Monday consultation with city staff.
Permit and PG&E
Online submittal, a 60 day or 30 day review clock, and the PG&E service application filed alongside.
Build and final
Foundation, framing, inspections, new address, deed restriction recorded, then the certificate of occupancy.
CITY FEES, NOT CONSTRUCTION
Plan for ADU permit fees.
Permit and review fees depend on the project. Check the current city fee schedules and confirm the applicable charges with Milpitas before budgeting.
| Permit cost | Where to confirm |
|---|---|
| Building permit and plan review | City fee schedules |
| Other project-specific charges | Confirm with the city and the relevant agencies |
BEFORE YOU APPLY
What Milpitas asks for.
Check first
- Flood zone and Building Code Restriction fields in the city's parcel lookup
- Zoning that allows single-family or multifamily use
- Easements on the title report
- A free ADU Monday appointment, or email adu@milpitas.gov
Budget for these city items
- Fire Department review, $703, if sprinklers are required
- School impact fee once the ADU exceeds 500 sq ft
- Water connection, $1,910 prorated by ADU size
- Sewer connection, $1,908, and treatment plant fee, $880, both prorated
Expect a Minor Site Development Permit when
- A pre-approved plan exceeds 800 sq ft
- The ADU does not meet the standard setbacks or height
- The design departs from the city's ADU standards
- Lot coverage would exceed 50 percent
How big can an ADU be in Milpitas?
Up to 1,200 square feet for a detached ADU under Milpitas zoning section C.10.030. An attached ADU is limited to 50 percent of the main home but can always reach 800 square feet, and a junior ADU is limited to 500 square feet. Conversions of existing space can exceed these limits.
How many ADUs can I build on a single-family lot in Milpitas?
Up to three units: one attached ADU, one detached ADU and one junior ADU on a lot with a single-family home. Lots with an existing multifamily building can add up to 8 detached ADUs, as long as ADUs do not outnumber the existing units.
How long does Milpitas take to review an ADU permit?
60 days from a complete application, or 30 days with a pre-approved ADU plan, under section C.10.030.D. The city must either approve the application or send a notice of deficiency in that time, and the same clock applies to resubmittals.
Can I use a pre-approved ADU plan in a Milpitas flood zone?
Only if the plan includes a flood-resistant design option for the site. Properties in FEMA zones A, AE, AH or AO are otherwise not eligible, and properties in the Hillside Building Code area east of North Park Victoria Drive, Evans Road and Piedmont Road are not eligible at all.
What are the city fees for an ADU in Milpitas?
About $5,255 at minimum for an 800 square foot ADU in building, planning and land development fees, per the city's FY 2025-26 estimate. No impact fees apply under 750 square feet, a new address costs $709, and water and sewer connection fees are prorated by size.
Can I rent out or sell an ADU in Milpitas?
Rent yes, sell no. Milpitas allows ADUs to be rented for terms of 30 days or more, but an ADU cannot be sold separately from the main home unless a qualified nonprofit built it. A deed restriction stating this is recorded before occupancy.
