STATEWIDE UPDATE: New California ADU Bills SB13, AB68, AB881, AB670 have passed. These laws will create more options for building an ADU in Belmont in 2020. To prepare for the upcoming changes use our ADU Services to learn how these laws will effect your property!
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Belmont ADUs

Everything about building Accessory Dwelling Units in Belmont, CA

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Belmont ADU Guidelines Last Updated 08/11/19


The city government of Belmont has updated its local zoning codes to comply with the State ADU mandate.
The California Building Code (CBC) 2016 is adopted with the following amendment(s): 2016-1112
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:

One ADU unit allowed only on parcels on which only one dwelling
Unit is located.

AB68 & AB881 Update: Properties which convert existing space to create ADUs may be eligible for one ADU -AND- one JADU.

Types of ADUs allowed:

Detached, Attached and junior ADUs.

Lot size:

Lot size. An ADU unit is allowed on lots of 5,000 square feet or More. An ADU unit may be permitted on a lot of less than 5,000 Square feet with a Conditional Use Permit.

AB68 & AB881 Update: Properties will not be subject to minimum lot standards by ordinance or of the applicable zoning district.

ADU size:

Minimum Unit Size. Notwithstanding subsection (d), an efficiency ADU of Up to 275 square feet is allowed with approval of a building permit. Maximum Ministerial Unit Size. An ADU not exceeding 50% of the total Habitable floor area of the principal dwelling is allowed with approval of a building Page 2 of 5 Permit if it is: (1) A detached ADU not greater than 399 square feet. (2) An attached ADU not greater than 640 square feet.

AB68 & AB881 Update: Properties will be allowed up to 850 square feet for a one bedroom or up to 1,000 square feet for a two bedroom ADU.


Setbacks are determined by the standards of the underlying zone.

AB68 & AB881 Update: The maximum required setback for a detached new construction ADU shall be no more than 4 feet from the rear or side property lines.


Off-Street Parking. The property must meet the parking space and standards for
ADU units in Section 8. Spaces provided shall meet the size
Requirements in Section 8.3.1 and must be paved and located wholly upon the
Property in fee, except as provided in Section 8.2.6. parking spaces may be
Permitted in tandem in the driveway and within the garage or carport.

AB68 & AB881 Update: Properties which convert an existing garage will not be subject to replacement parking requirements.

Fire Safety:

Per state requirements.

Shape, materials and style:

Architectural compatibility with the primary home, including exterior color, materials, and characteristics.


Subject to the requirements of the underlying residential zone.

Design review:

ministerial review process per state requirements.
Design Standards for ADUs (attached and detached ADUs). ADU additions shall comply with the following design standards:
➤ ADU additions must comply with the Residential Design Criteria (RDC) if the new
construction includes: 1) ground floor plate height exceeds feet or roof height exceeds feet (as measured from finished grade); or 2) creates or expands an upper floor.
➤ ADUs shall be constructed with facade materials identical in color, and similar in texture and appearance to the primary dwelling, including but not limited to roofing, siding, and windows and doors.
➤ ADUs shall match the roof pitch/form of the primary dwelling in order to blend with the architecture of the primary dwelling.

Number of Bedrooms:

Not specified by State Standards.


Unit is not intended for sale separate from the primary residence and may be rented. (State requirements)

SB13 Update: Owner-occupancy requirements for ADUs will be voided statewide for 5 years.

Utility connections:

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

Permit Fees

SB13 Update: Local impact fees for ADUs will be reduced substantially statewide.


Exception to Maximum Ministerial Unit Size. Second units larger than allowed
with a building permit under subsections (c) and (d) are permitted with approval
of single family design review and a Second Unit Floor Area Exception under
Section 24.5.

Floor area exceptions, see Section 5 (24.5) here:

Allowed Zones:

Authority and Purpose. This section regulates the establishment of secondary dwelling
units in all residential zoning districts in accordance with Government Code Section
65852.2. The purpose of permitting secondary units is to promote more efficient use of
the City's existing housing stock and to help meet the need for small rental units while
preserving the character of the City.

Zoning Requirements. The secondary dwelling unit must meet all site area,
density, height and yard area standards of the R-1 zoning district.

AB68 & AB881 Update: ADUs will be allowed statewide in all single-family or multi-family zoning districts.


Location. Secondary dwelling units are allowed in conjunction with a single family
dwelling located in the following residential zoning districts:
(a) R-1, R-2, R-3, and R-4 Districts.
(b) HRO Hillside Residential & Open Space districts upon approval of a Conditional
Use Permit by the Planning Commission.

Residential Building Code:

The California Building Code (CBC) 2016 is adopted with the following amendment(s): 2016-1112

Belmont ADU Marketplace

How can I get my ADU built?

Use our ADU Services and Marketplace to get expert assistance, permit-ready ADU designs and on-site contractor estimates on one platform.

Fast and low cost ADU design services

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Featured Financing Program

ADU Financing

CA Statewide

Tailored to ADU construction.

Based on project size & appreciation.

Learn how to qualify.

Karyn Jones

Program Representative

Call Now (760) 496-5959

Read Belmont Housing Market Update

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A recent customer review:

"This was a great place for us to start the investigation into building an ADU. The nominal investment to get most of the ADU parameters established is money well spent."

Kevin in Los Altos, CA

Customer since January, 2019

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Costs / ROI


* upon completion of ADU


* based on local average price per sqft


* estimated by location


* 30 years / 5% interest rate / 20% down payment


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

Rental Estimate = (Rent Per Sqft: $5.60) * (ADU's Living Space: sqft)

How can I get my ADU built?

Our ADU Services and ADU Marketplace provide the fastest and lowest cost way to get started with your ADU project.

How does it work? Get started on your project with expert assistance and without commitment using our customized ADU Property and Design Reports as your first step. Then, get on-site visits from local contractors who can provide you with guidance and estimates for your ADU project.

Our Key Advantages

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Get started on your timeline and your terms, without commitment

The fastest and lowest cost way to get started with your ADU project

Our ADU Process

Expert Feasibility & Zoning Research

Use our ADU Property & Design Reports as a starting point to plan your ADU project. Our experts will do the legwork with your city or county planning office and design custom ADU concepts for your property and your needs.

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Use our local contractor database to get on-site visits and cost estimates to compare services for your ADU project.

Getting your designs ready for city permitting and construction can speed up your ADU project and reduce unforseen costs later on in the process.

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