California ADU rules · San Mateo County
Can I Build an ADU in Menlo Park?
Yes — you can build an ADU in Menlo Park. California's statewide ADU law requires every city, including Menlo Park, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local ruleMaximum of three units total (primary + ADU + JADU); only one JADU or one attached/interior ADU allowed, not both
Units on a multifamily lot
Local ruleAt least one ADU within existing non-livable space, up to 25% of existing units as ADUs; up to two detached ADUs per lot
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,000 sq ft
Local maximum for detached ADUs is 1,000 sq ft; no more than two bedrooms
Max attached ADU size
Local ruleGreater of 1,000 sq ft or 50% of the existing primary dwelling’s floor area; no more than two bedrooms
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
CA state law16 ft
16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
Local ruleSame as required for primary dwelling
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
Local ruleUp to 1 space
1 off-street space per ADU; JADUs exempt
Transit parking exemption
Local ruleYes — no parking required near transit & for conversions
No parking required if within ½ mile of transit, in historic district, interior ADU, or within 1 block of car share
Garage-conversion replacement parking
Local ruleNot required
No replacement parking required for garage conversions
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
Owner-occupancy required only for JADUs
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
Local ruleBuilding permit, ADU/JADU checklist
Checklist must be submitted with application
Menlo Park caps detached ADUs at 1,000 sq ft and allows only two detached ADUs on multifamily lots. Setbacks and height limits are stricter for detached ADUs over 800 sq ft, and owner-occupancy is required only for JADUs.
Frequently asked questions
Can I build an ADU in Menlo Park?
Yes. California's statewide ADU law requires Menlo Park to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Menlo Park?
A detached ADU of at least 1,000 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Menlo Park?
Side and rear setbacks are limited to 4 ft. Same as required for primary dwelling.
Is parking required for an ADU in Menlo Park?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Menlo Park?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Menlo Park?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Menlo Park Municipal Code Chapter 16.79 (Accessory Dwelling Units), Ord. 1066 (2020), Ord. 1096 (2023)
- § 16.79.050(a)
- § 16.79.090(a)-(b)
- § 16.79.030(b), § 16.79.050(c), § 16.79.060(b)
- § 16.79.030(a), § 16.79.050(b)(3)
- § 16.79.060(c)-(d)
- § 16.79.080(a)-(b)
- § 16.79.080(b)
- § 16.79.080(c)
- § 16.79.070(b), § 16.79.120
- § 16.79.100
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Menlo Park's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Menlo Park Planning before relying on it.
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