800 sq ft ADU · checked Oct 18, 2026
800 sq ft ADU fees in Milpitas: $5,964–$12,850, $386 more than at 750 sq ft
Milpitas charges no impact fees that we model, so going from 750 to 800 sq ft adds only $386 in size-based fees such as school fees and permits.
750 vs 800
What the extra 50 sq ft changes in Milpitas
- Water connection fee: $0–$716 at 750 sq ft → $0–$764 at 800 sq ft
- Sewer connection fee: $0–$716 at 750 sq ft → $0–$763 at 800 sq ft
- Treatment plant fee (new sewer connection): $0–$330 at 750 sq ft → $0–$352 at 800 sq ft
- School fee (statewide cap shown): $0–$4,035 at 750 sq ft → $0–$4,304 at 800 sq ft
Staying at 750 sq ft would save about $386 in fees under today’s law.
Line by line: 750 sq ft vs 800 sq ft, now and under SB 1117
Detached ADU, 2,000 sq ft main home (example assumption). The 2027 column applies SB 1117, which limits impact fees to the area over 750 sq ft.
| Fee | 750 sq ft (2026) | 800 sq ft (2026) | 800 sq ft (from 2027) |
|---|---|---|---|
| Building permit & plan check | |||
| Building, planning and land development permit fees (City estimate table) | Est.$5,255 | Est.$5,255 | Est.$5,255 |
| New address request permit | $709 | $709 | $709 |
| Fire sprinkler review | May apply$703 | May apply$703 | May apply$703 |
| Impact fees | |||
| Park in-lieu fee | Exempt | $0 | $0 |
| School district fee | |||
| School fee (statewide cap shown) | Up to$4,035 | Up to$4,304 | Up to$4,304 |
| Utility connections | |||
| Water connection fee | May apply$716 | May apply$764 | May apply$764 |
| Sewer connection fee | May apply$716 | May apply$763 | May apply$763 |
| Treatment plant fee (new sewer connection) | May apply$330 | May apply$352 | May apply$352 |
| Modeled total | $5,964–$12,464 | $5,964–$12,850 | $5,964–$12,850 |
State law
Why 800 sq ft is the size every city must allow
Local limits on lot coverage, floor area ratio, open space and minimum lot size can’t stop an 800 sq ft ADU with 4 ft side and rear setbacks, and a detached unit of up to 800 sq ft must be approved ministerially alongside a junior ADU.
Gov. Code §66321(b)(3)
size based upon a percentage of the proposed or existing primary dwelling, or limits on lot coverage, floor area ratio, open space, front setbacks, and minimum lot size, for either attached or detached dwellings that does not permit an accessory dwelling unit with at least 800 square feet of interior livable space and with four-foot side and rear yard setbacks to be constructed in compliance with all other local development standards.
Gov. Code §66323(a)(2)
One detached, new construction, accessory dwelling unit that does not exceed four-foot side and rear yard setbacks for a lot with a proposed or existing single-family dwelling.
Gov. Code §66323(a)(2)(A)
A total floor area limitation of not more than 800 square feet of livable space.
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 800 sq ft adu in Milpitas
How much are the fees for an 800 sq ft ADU in Milpitas?
Our model of Milpitas’s official schedules comes to $5,964–$12,850 for a detached 800 sq ft ADU with a 2,000 sq ft main home, compared with $5,964–$12,464 at 750 sq ft.
Does an 800 sq ft ADU pay impact fees in Milpitas?
No impact fees that we model. State law would allow proportional impact fees above 750 sq ft, but Milpitas’s schedules we use don’t charge any for this ADU.
Can Milpitas stop me from building an 800 sq ft ADU?
Not with lot coverage, floor area ratio, open space or minimum lot size limits. State law requires cities to allow at least an 800 sq ft ADU with 4 ft side and rear setbacks (Gov. Code §66321(b)(3)), provided it meets other objective standards such as height.
Do school fees apply at 800 sq ft?
Yes. School fees apply above 500 sq ft; at 800 sq ft the statewide Level 1 cap is $4,304, and many districts charge less.
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)