Belmont Accessory Dwelling Unit (ADU) Standards

        New laws were recently passed, and updates will be coming soon

Planner on Duty - 650.595.7478
ADU Ordinance

Zones allowed

All residential zones (R-1-5, HRO, PD)

Lot restrictions


Minimum lot size
Min / Max ADU size

Min: None

Max attached: lesser of 50% of primary dwelling or 800 sf

Max detached: 800 sf

ADU building height

Attached: 28 feet

Detached: 15 feet

Over garage: 17-20 feet (dependent on roof style)


5 feet rear and side
Parking requirements

No parking required but, if provided, can be tandem

Owner occupancy

Owner must live in the main dwelling or the ADU

Sample fees from recently built projects*

ADU 1 (584 sf, attached): $6,736

ADU 2 (416 sf, attached): $3,404

ADU 3 (285 sf, attached, junior): $3,399

Other requirements
  • Sprinklers for fire safety are required if the ADU results in a 50% increase in the original size of the residence or a combination of increase in size and remodeling impacted 50% of the original square footage. The state building code requires sprinklers for all new construction.
  • All projects removing trees are subject to the Belmont Tree Ordinance.
  • A restrictive covenant must be recorded on the deed prior to finalizing the building permit and issuance of occupancy.
  • ADUs are not allowed in front of the primary dwelling unless the structure is already in front of the primary residence.
  • Only one ADU per property is allowed.
  • ADUs are not allowed on sites with multifamily dwellings.
  • ADUs must comply with all requirements of the underlying zoning district.

Building permit review required. No design review of ADU is required, even if ADU is part of a larger project. Making an appointment to meet with a planner in the initial stages of the project can help avoid challenges and is highly recommended.



Disclaimer: standards and process may vary. Consultation with the contact is recommended before starting any project.

*Fees are specific to each project and will vary. Fees change regularly. These are provided as examples only.

Download ADU Standards PDF

Updated: 12/11/2017