San Mateo County

Menlo Park ADU rules

Research summary of local ADU rules on file for City of Menlo Park in San Mateo County. Not a determination for a specific lot.

Last checked October 23, 2026.

City or county ADU page

Menlo Park Planning department. No ADU-specific page was found.

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City of Menlo Park rules on file

Local rules recorded in this project for this jurisdiction. Where a city figure on file is stricter than the state baseline on file, both are shown.

ADUs on the state’s simple path
Single-family lots can have one conversion ADU, one junior ADU and one detached ADU up to 800 sq ft with 4 ft side and rear setbacks, 16 ft tall (18 ft near major transit, plus 2 ft to match the roof pitch). These need only meet those limits.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.050, accessed 2026-10-23.

Multifamily lots
Conversions of non-living space: at least one and up to 25% of existing units. Detached: up to eight on lots with existing multifamily buildings (not more than existing units) or two with a proposed building; 4 ft setbacks; 16 ft, 18 ft near transit or with a multistory building.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.050, accessed 2026-10-23.

Junior ADUs
150 to 500 sq ft inside a single-family home, plus up to 150 sq ft for entry. One per lot. Efficiency kitchen required. Owner occupancy applies only when it shares a bathroom with the main home. A deed restriction against separate sale is recorded. No parking.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.060, accessed 2026-10-23.

Larger and attached ADUs
ADUs outside the simple path: 150 sq ft minimum, up to 850 sq ft (one bedroom or less) or 1,000 sq ft (more than one bedroom). Add 100 sq ft if the ADU meets accessibility code. Only one such ADU per lot.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.070, accessed 2026-10-23.

800 sq ft allowance
Floor area, lot coverage, open space and parking rules cannot block an ADU of at least 800 sq ft with 4 ft side and rear setbacks. The front setback also yields as needed. If this allowance is used, the main home gets its final inspection before the ADU.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.070(b), accessed 2026-10-23.

Height and setbacks
Attached: 25 ft or the zone limit, whichever is lower, plus the daylight plane. Detached: 16 ft (18 ft near major transit plus 2 ft for roof pitch; 18 ft with a multistory multifamily building). 4 ft side and rear setbacks; eaves may extend 18 in. Stairs and landings stay 4 ft from side and rear lines.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.070, accessed 2026-10-23.

Access and design
Own exterior entrance and an all-weather path from the street. Internal access to the main home needs two fire-rated doors with separate locks. Covered porches up to 20% of the ADU’s floor area are treated as part of the ADU. Exterior lighting must be shielded and aimed downward.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.070, accessed 2026-10-23.

Parking
No parking is required; garages converted or removed for an ADU don’t need replacement.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.070, accessed 2026-10-23.

Review timelines
Ministerial building permit. Completeness within 15 business days; decision within 60 days or the application is deemed “approved”. Appeals go to the Planning Commission within 15 days.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.080, accessed 2026-10-23.

Older unpermitted units
Units built before Jan. 31, 2023 can be legalized without being denied over building or zoning issues unless a health and safety correction is needed. Impact fees don’t apply.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.080(e), accessed 2026-10-23.

Sewer
A letter confirming sanitary capacity is required (West Bay Sanitary District for septic lots).
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.080(i), accessed 2026-10-23.

Rentals and sale
No rentals under 30 days. No separate sale unless state rules for separate conveyance are met.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.080(l), accessed 2026-10-23.

Lot splits
No ADUs or junior ADUs on single-family lots that used both an SB 9 lot split and an SB 9 two-unit project.
Source: City of Menlo Park Municipal Code Chapter 16.79 (Ordinance 1129, June 9, 2026), 16.79.090, accessed 2026-10-23.

California state rules on file

The statewide baseline recorded from state law and the HCD ADU Handbook.

Detached size cap described in state law
1,200 sq ft. Recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Side and rear setback cap for a new ADU
4 ft. Recorded in this rules file from Government Code section 66314, which describes a cap on side and rear setbacks for a new ADU.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Setback for a conversion of an existing structure
No additional setback, as recorded in this rules file from Government Code section 66314 for a conversion of an existing structure.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Minimum lot size
A city may not impose a minimum lot size for an ADU, as recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Minimum unit the handbook says cities must allow
At least an 800 sq ft ADU with 4 ft side and rear setbacks. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(3).
Source: HCD ADU Handbook, 66321(b)(3); handbook updated March 2026, accessed 2026-10-16.

Detached height described in the handbook
16 ft, or 18 ft or 20 ft in some cases. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(4).
Source: HCD ADU Handbook, 66321(b)(4); handbook updated March 2026, accessed 2026-10-16.

Permit decision deadline
60 days. Recorded in this rules file from Government Code section 66317(a)(3): the permitting agency must decide on (approve or deny) a completed ADU application within 60 days when an existing single-family or multifamily dwelling is on the lot. Section 66317(a)(1) says the application is considered ministerially, without discretionary review or a hearing.
Source: California Government Code section 66317, 66317(a)(1), (a)(3), accessed 2026-10-17.

Owner-occupancy requirement
None. Recorded in this rules file from Government Code section 66315: a local agency may not impose an owner-occupancy requirement on an ADU. It may require that the property be used for rentals of terms 30 days or longer. The HCD ADU Handbook (updated March 2026) describes the same rule.
Source: California Government Code section 66315, 66315; HCD ADU Handbook updated March 2026, accessed 2026-10-17.

Parking near public transit
No parking standards within one-half mile walking distance of public transit. Recorded in this rules file from Government Code section 66322(a)(1). Section 66322(a) lists several other cases where parking standards may not be imposed.
Source: California Government Code section 66322, 66322(a), accessed 2026-10-17.

Ministerial categories
The HCD ADU Handbook (updated March 2026) states that Government Code section 66323 sets four ministerial categories. This rules file does not restate those four categories.
Source: HCD ADU Handbook, 66323; handbook updated March 2026, accessed 2026-10-16.

Fire Hazard Severity Zones
If your lot is in a Fire Hazard Severity Zone, the CAL FIRE Office of the State Fire Marshal says in Information Bulletin 25-004 (issued March 3, 2025): “Fire Hazard Severity Zones (FHSZs) should not restrict the development of Accessory Dwelling Units (ADUs). However, additional building standards may be necessary, including but not limited to California Fire Code Chapter 49 and California Building Code Chapter 7A.” State ADU law does not itself bar an ADU there. A city or county may still apply its building code, including wildfire-resistant construction (Gov. Code 66314(d)(8)); require side and rear setbacks “sufficient for fire and safety” for a unit converted under 66323(a)(1); and decline parking in setbacks on specific fire and life safety findings (66314(d)(10)(B)). It may also consider public safety when it designates where ADUs may be permitted (66314(a)). Sprinklers can't be required in an ADU or JADU if the primary residence doesn't need them (66314(d)(12), 66323(d)). Some cities and counties still apply their own fire-zone limits. Where this summary has one, it is listed with the local rules. This summary does not look up your lot. Check the CAL FIRE Fire Hazard Severity Zone map viewer linked from the State Fire Marshal's Fire Hazard Severity Zones page: https://experience.arcgis.com/experience/5065c998b4b0462f9ec3c6c226c610a9
Source: CAL FIRE Office of the State Fire Marshal Information Bulletin 25-004, page 4, issued March 3, 2025; Gov. Code 66314, 66323, accessed 2026-10-20.

State baseline on the directory → · State ADU rules on the homepage →

Can I build an ADU in Menlo Park?

State law sets a baseline for ADUs in Menlo Park, and the local standards on file are listed on this page. Whether a specific lot can add an ADU depends on zoning, utilities, and other site facts this page does not measure. Confirm with City of Menlo Park Community Development Department, or run a free address summary.

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