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Permit guides

ADU Permits in Milpitas: a Homeowner's Guide

What you can build, which permits you need, and how the review actually works — in plain language.

Last updated October 2026. Rules change; always confirm current requirements with the city before you build.

Who handles your permit

The City of Milpitas Community Development Department — Building Safety & Housing Division issues ADU permits from City Hall, 455 E. Calaveras Blvd. (408-586-3240, BuildingPermitCenter@milpitas.gov). Submittals go through the city's Online Submittal System as electronic plan sets — expect an email within about two weeks with your initial fee.

What you can build

California state law sets the baseline, and Sunnyvale follows it:

There is no minimum lot size for an ADU under state law. Converted garages and other existing structures keep their current footprint — no new setbacks apply to the conversion itself.

A pre-approved program with a narrow footprint

Milpitas runs a Pre-approved ADU Program — but not as a downloadable plan library. Instead, the city accepts master-plan submittals from qualified professionals for pre-approval of detached ADU plans suited to standard site conditions.

Two limits to know up front: the program does not apply in hillside areas (MMC sec. II-1-2.01), flood zones, or zoning districts other than R-1 and R-2 — and plans over 800 sq ft must also meet extra standards in MMC sec. XI-10-13.08(F).

The city also publishes an ADU Toolkit walking homeowners through the process, and has operated an ADU Incentive Program helping cover permit costs (averaging about $5,000 per ADU) — ask whether funding is currently available.

What goes into the submittal

1. Electronic plan set through the Online Submittal System — minimum 22"x17" plot size, drawings to scale (1/8" = 1'-0" minimum for floor plans).
2. Decide on utilities early. Separate utility connections to the ADU (water, sewer, gas) add permit and utility fees; shared connections avoid that bill. Removing trees requires a Tree Removal Permit — handle it before it becomes a correction.
3. Fees and corrections. No impact fees for a JADU or an ADU under 750 sq ft; at 750 sq ft and above, a school impact fee plus proportional impact fees apply. Respond to review comments and resubmit until every reviewer signs off.

Where applications usually get stuck

• Hillside and flood-zone lots are excluded from the pre-approved program entirely — expect a full custom review.
• The 750 sq ft fee line — school impact fees kick in here, so a design drifting just over the line changes the budget.
• Separate utility connections — new service lines mean new fees and capacity charges; coordinate with the providers before finalizing the design.