Bay Area region / California
Belmont ADU rules
& permit guide.
Planning an ADU in Belmont? Review local size, setback and parking requirements, then confirm the details for your property with the permitting agency.
Local source collected 2026-05-20 · View sources
Local requirements at a glance
Min/max ADU size
Min: 150 square feet Max detached (one bedroom or less): 850 square feet Max detached (two bedrooms or more): 1000 square feet Max attached: the greater of 50% of primary dwelling square footage or 850 square feet (one bedroom or less) / 1,000 square feet (two+ bedrooms)
Height
Attached: Same as primary dwelling Detached: 16 feet Over garage: 20-23 feet (dependent on roof style) *Over garage, if setbacks meet underlying zoning regulation: 28 feet
Setbacks
Attached: California Gov. Code, § 65852.2, subd. (a)(1)(D)(vii): 4-feet side and rear Detached: rear and side – 4 feet; front – depends on zoning district; 5 feet from primary dwelling unit
Parking
No parking required but, if provided, can be tandem
Process
Confirm your parcel and ADU type with the local planning department, prepare the required plans, and follow the city's building permit checklist. Ask which utility, fire and site reviews apply before submitting.
Your next three steps
- Confirm the property's jurisdiction, zoning and site constraints with Belmont's planning department.
- Discuss the ADU type, dimensions and utility needs with your designer before finalizing a layout.
- Ask the permitting agency for its current application checklist, fee estimate and review process.
2026 state-law context
ADUs and JADUs have different occupancy rules
California generally prohibits local owner-occupancy requirements for ADUs. A narrow exception applies to certain separately sold affordable ADUs. For JADUs, owner occupancy generally applies when the bathroom is shared with the main home; separate-bathroom JADUs are treated differently under 2026 law. Check the HCD handbook and your project's permit conditions.
Older local summaries may not reflect the latest state changes. Read HCD’s March 2026 handbook, pages 32–33.
Questions for your first planning conversation
- Which approval path applies to my building and ADU type?
- Do easements, trees, slope, access or fire conditions affect placement?
- Which utility upgrades and agency reviews should be included in my budget?
- Are preapproved plans available, and what site work still needs review?