Statewide Update: New California ADU Bills AB68, SB13, AB881, AB670 have passed. These laws create more options for building an ADU in 2020. Use ADU Services to learn how they affect your property!

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Menlo Park ADU Guidelines Last Updated 03/27/20


The city government of Menlo Park will approve ADUs under California's statewide mandated regulations.
The California Building Code (CBC) 2019 is adopted.
Relevant state bill updates for SB13, AB68, AB881, AB670 are shown in green below.


City Hint: The city has not yet responded to requests for ADU permit volumes for the past year, but they will be provided here once response has been received.


Number of ADUs allowed:

According to state law, all single-family homes are allowed at least one Accessory Dwelling Unit (ADU). Additionally, single-family parcels which are owner-occupied may create one Accessory Dwelling Unit (ADU) and one Junior Accessory Dwelling Unit. Also, multi-family parcels may now add one ADU per every four existing residential units, so long as they were legally established.

As of January 1st, 2020

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are allowed. ADUs may be new construction or converted from existing space. JADUs must be converted from existing space.

Lot size:

Single family and multi-family residential properties will not be subject to the minimum lot size of the underlying zoning district or by ordinance for ADU projects. ~ AB-68

As of January 1st, 2020

ADU size:

Residential lots will be approved to construct up to 850 sqft for a one bedroom ADU or up to 1,000 sqft for a two bedroom ADU, regardless of the underlying zoning standards of the property. A Junior Accessory Dwelling Unit is approved up to 500 sqft. According to Califronia Residential Code, the minimum size of any living unit is 150 sqft (including Accessory Dwelling Units and Junior Accessory Dwelling Units). ~ AB-68

As of January 1st, 2020


Setbacks for a detached new construction Accessory Dwelling Unit (ADU) shall be no more than 4 ft from the rear and side lot lines. No setbacks shall be required for Accessory Dwelling Unit (ADU)s and Junior Accessort Dwelling Unit (JADU)s converted from legally eastablished existing space. Attached new construction Accessory Dwelling Unit (ADU)s and conversions from existing space to be expanded must comply with the setbacks of the underlying zone. ~ AB68 & AB881 Update

As of January 1st, 2020


Replacement parking shall not apply to properties which convert an existing garage to an Accessory Dwelling Unit (ADU) or Junior Accessory Dwelling Unit. ~ AB68 & AB881 Update

As of January 1st, 2020

Fire Safety:

Accessory dwelling units shall not be required to provide fire sprinklers if they are not required for the primary residence and may employ alternative methods for fire protection. (State requirements)

Shape, materials and style:

The details required for the building permit plan set depend on the type of ADU unit
and are described in Building Division handouts. Please see the relevant links below, based on the
type of ADU unit proposed:
 A new detached ADU unit:
 Conversion of an existing accessory structure into a ADU unit with no new
square feet :
 A new ADU unit, less than 500 square feet in size, attached to the main
residence or an existing accessory structure:
 A new ADU unit, more than 500 square feet in size, attached to the main
residence or an existing accessory structure:

Unit shall have the colors, materials and textures and architecture
similar to primary dwelling unit


Attached ADUs shall comply with the height requirement for the zoning district, and detached ADUs are limited to single story and 17 feet.

Design review:

ADU units that are designed in compliance with the development regulations established in Chapter 16.79 of the Zoning Ordinance are not subject to discretionary review, with the exception of certain projects that alter/expand existing nonconforming structures. Please see the nonconforming structures handout ( for more detail, and check with the Planning Division for specifics. A modification to the development regulations, except the density and subdivision standards, may be granted through the use permit process by the Planning Commission. An interior side and/or rear yard may also be reduced to feet subject to written approval of the owner(s) of the contiguous property abutting the portion of the encroaching structure. (Please see page 3 of this handout.) Note that a survey may be required to determine whether an existing structure is conforming or not, and also that all use permit applications require a full site survey. In all cases, building permits are required prior to any construction.
The following are the steps in the review and approval process: 1) The applicant submits a complete
building permit application and fees for the ADU unit, including plans showing the
details of the proposed ADU unit (please see next question), and the ADU unit checklist (, 2) The
City of Menlo Park – Community Development Department, Planning Division Page 2 of 5
ADU Units
Updated July 2017 community development director or his or her designee makes a determination of compliance, 3)
The application is either approved within 120 days after receipt of a substantially complete application, or the application is denied if the proposed ADU unit does not comply with all applicable requirements. Alternatively, the application may be approved subject to conditions that will bring the proposed ADU unit into compliance with the development standards.

Number of Bedrooms:

1 bedroom (maximum)
1 bathroom (maximum)


Owner-occupancy will not be required for new Accessory Dwelling Units (conversion and new construction) built between 2020 and 2025. ~ Updated: State Law SB-13

As of January 1st, 2020

Utility connections:

Local health officer approval where a private sewage disposal system is being used, if required. (State requirements)

Permit Fees

SB13 Update: As of January 1st, 2020, local impact fees for ADUs will be reduced substantially statewide.


16.04.295 Dwelling unit, secondary. A "secondary dwelling unit" (which is referred to as an “accessory dwelling unit” in State law) means a dwelling unit on a residential lot which provides complete independent living facilities for one or more persons, and shall include permanent provisions for living, sleeping, eating, cooking, and sanitation independent of the main dwelling existing on the residential lot. For purposes of a secondary dwelling unit, permanent provisions for eating and cooking include the following: (1) permanent range, (2) counters, (3) refrigerator, and (4) sink. There are two (2) types of secondary dwelling units: (1) units attached to the existing dwelling, including units located within the living area of an existing dwelling unit (“Attached Secondary Dwelling Units”); and (2) units detached from the existing dwelling unit and located on the same lot as the existing dwelling unit (“Detached Secondary Dwelling Units”).


My neighbor has approved a reduced side yard and/or rear yard setback for my secondary
dwelling unit. What documentation do I need?
A. Per Chapter 16.79.040(5)(B) of the Zoning Ordinance, an interior side or rear yard for a detached
secondary dwelling unit may be reduced to 5 feet subject to written approval of the owner(s) of the
contiguous property abutting the portion of the encroaching structure. Written documentation shall
consist of the following items and must be submitted as part of the building permit application.
1) Completed statement letter (
from the contiguous property owner(s) acknowledging the approval of a reduced setback from
the required zoning district standard for the main dwelling unit (indicate the setback
requirement) to the agreed upon setback (indicate the setback in feet, but cannot be less than
five feet). The statement shall be notarized by the property owner(s) listed on the title of the
2) If neighbor approval of a reduced setback is contingent upon a specific site plan and/or other
design feature, please include a specific reference to the plan in the statement letter. In
addition, please attach the plan as an exhibit. The plan must be signed and dated by both the
property owner(s) and the contiguous property owner(s).
Alternatively, the Planning Commission has the authority to approve a use permit to reduce the
required setback requirements for a secondary dwelling unit. Please contact the Planning Division to
learn more about the use permit process.

Allowed Zones:

*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***

As of January 1st, 2020

Existing Structures

Potentially. An accessory building that received building permits and commenced construction prior to January 1, 2017 may be converted into a secondary dwelling unit so long as the following criteria are met: 1) a building permit or other supporting documentation is provided to show the structure was legally built, 2) the building can be upgraded to meet the Building Code requirements for a dwelling unit, and 3) the accessory building complies with the development regulations of a secondary dwelling unit, with the exception of minimum yards, height, daylight plane, and parking. City of Menlo Park – Community Development Department, Planning Division Page 3 of Secondary Dwelling Units: Updated July 2017 All or any portion of an accessory building that meets the above eligibility criteria may be demolished and reconstructed to meet building code requirements based on the change of occupancy at the time of conversion. The secondary dwelling unit that replaces the accessory building may retain the setbacks and the footprint of the legally constructed accessory building. If the lot is smaller than the required 6,000 square feet, or the proposed secondary dwelling unit exceeds the permitted unit size as described in the development regulations summary table on the last page of this handout, a use permit may be requested to deviate from one or both of these standards. A use permit is a discretionary process, which requires Planning Commission review and approval.

SB13 Update: Amnesty program to permit unpermitted units will be administered statewide, allowing non-health and safety code violations to be deferred.

Building Code:

Comply with all applicable development regulations for the singlefamily
zoning district and building code requirements

Daylight Plane

Is there a daylight plane requirement for secondary dwelling units?
A. Yes, a detached secondary dwelling unit has a separate daylight plane requirement that must be met, unless a use permit is approved to deviate from this secondary dwelling unit standard. The daylight plane for a detached secondary dwelling unit is established at a line three (3) feet from the side property lines. The daylight plane begins at a horizontal line 9 feet, 6 inches above the average grade with a slope inwards at a 45 degree angle. There are no permitted intrusions into this daylight plane. The daylight plan requirement for an attached secondary dwelling unit is the same as the daylight plane required for the primary residence.
Daylight plane shall begin at a horizontal line 9 feet, 6 inches
above the average natural grade at a line 3 feet from the side
property lines, and slope inwards at a 45 degree angle.

Property Taxes

Property taxes are assessed by the County of San Mateo Assessor’s Office, not by the City of Menlo Park. Like other development projects in the City, the County collects information from the City when building permits are issued to a property. Please contact the County Assessor’s Office for more information about how the information is used.

Legalizing Existing Units

Contact the City of Menlo Park Planning or Building Divisions for research on the property. The County of San Mateo Assessor’s Office can also be a good resource for historical property information.

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

Menlo Park City Planning Offices


701 Laurel St. Menlo Park, CA 94025 Menlo Park, CA 94025

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* based on local average price per sqft


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Appreciation Estimate = (Base Value: $) / (Home's Living Space: sqft) * (ADU's Living Space: sqft)

Rental Estimate = (Rent Per Sqft: $6.82) * (ADU's Living Space: sqft)

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