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Contra Costa’s Requirements For Building An ADU

The world of building accessory dwelling units (ADUs) is an intricate one, and recent developments have made big changes to the landscape. Discover Contra Costa’s requirements for building an ADU in our latest blog post. There are specific regulations and guidelines that shape the processes of getting a permit and building an ADU in this vibrant California county. From zoning regulations to size guidance, we walk you through the things you need to know.

Whether you’re a homeowner exploring your options or a developer looking to navigate evolving laws, this comprehensive guide sheds light on Contra Costa’s ADU requirements. Get ahead of the legislation and make informed decisions as you embark on your ADU journey in total compliance.

Renee White
Written by Renée White
  / December 20, 2023

Renée White is a top-producing real estate broker with over 20 years of experience and an annual average of 200 sales. Clients are drawn to Renée for her deep knowledge of the local Contra Costa market.

Table of content
    • Contra Costa’s ADU ordinance lays out a detailed set of requirements for the planning, permitting, construction, and use of accessory dwelling units in the county.
    • Recent changes to statewide legislation have impacted ADU requirements in Contra Costa.
    • ADUs in Contra Costa can be no larger than 1,200 square feet and 16 feet tall.
    • An ADU must have its own kitchen and bathroom and function as a complete, independent dwelling separate to the main residence on the lot.
    • We are a leading real estate agency in Contra Costa and can assist with the planning, execution, and sale/renting of ADUs in the county.

    What Are Contra Costa’s ADU Requirements?

    Accessory dwelling units are known by many names. Whether you call them granny flats, guest houses, secondary units, or anything else, it’s important to understand Contra Costa’s ADU requirements if you want to navigate this area of the Contra Costa housing market. These constructions can be attached to the house, detached units, or conversions of existing buildings like standalone garages. The basic requirements for constructing an ADU in Contra Costa are as follows:

    • It must comply with the relevant zoning regulations.
    • You must obtain a permit from local authorities by submitting an application.
    • It must conform to size and setback requirements.
    • Local legislation for things like parking, design, and utilities must be complied with.

    In 2023, there were state-wide changes to ADU legislation in California that impacted Contra Costa. The updated laws made changes like enabling people to sell ADUs as condos, easing some of the restrictions around size and front setbacks, and making the 60-day rule for decisions on permits more transparent. Essentially, the new Assembly Bills and Senate Bills make it easier to secure a permit to build an ADU anywhere in California. But there is some variation between local regions, as many have put their own spin on the new rules.

    With that in mind, let’s look at the specific guidelines for ADUs in Contra Costa:

    • Detached ADUs: The maximum square footage for a detached ADU on a single-family residence is 1,200 square feet in Contra Costa. The rules are slightly different for multi-family lots, but detached unit height is limited to 16 feet.
    • Attached ADUs: These can be no larger than 50% of the square footage of the main residence, up to a maximum of 1,200 square feet. The maximum height is 25 feet or the height of the main residence – whichever is lower.
    • Converted ADUs: There are no restrictions on these, as the building already exists.

    If you are building an ADU in Contra Costa to rent or sell as its own dwelling, it will be subject to separate property taxes in Contra Costa. Let’s take a look at specific requirements for building an ADU in Contra Costa.


    Who Do You Need To Be?

    Contra Costa ADU requirements essentially state that, in order to build an ADU, you must be a property owner in the county with sufficient funds and space to build a compliant ADU on your land. So long as you own the lot, and are able to meet the rules as laid out in the ADU legislation, you can build an ADU on your land.

    What Income Do You Need?

    This depends entirely on the nature of your project. There are fees associated with obtaining a permit, and you will also need to pay for the design and planning of your ADU. There are also costs associated with the construction of the building. Generally speaking, you can expect to spend anything from $50,000 up to $300,000+ to have an ADU on your property ready to rent or sell in Contra Costa.

    Where Do You Need To Be?

    The requirements for ADUs in Contra Costa mean that you need to be located within Contra Costa County. Elsewhere, the specific ordinance may vary, so the rules may not be exactly the same. Also, you would need to submit your permit application to a different local authority.

    What Is Contra Costa’s ADU Ordinance?

    Contra Costa’s ADU ordinance is a set of regulations outlining the rules that govern the design, construction, and use of accessory dwelling units on residential properties. As detailed in the previous section, the ordinance addresses various considerations, including:

    • Zoning requirements
    • Design standards
    • Permitting procedures
    • Usage of the property

    Typically, ADU ordinance gives specifics about the maximum size of ADUs, setbacks from property lines, the ability to rent or sell the unit, and other specifications. One key consideration is compatibility with the existing neighborhood, and this has long been a bone of contention when it comes to planning departments. Recent changes in legislation make it more difficult for local authorities to block permits for ADUs in Contra Costa.

    The ordinance aims to strike a balance between the need for additional housing options and the preservation of the character of communities and neighborhoods. It must comply with state-mandated legislation to reflect California’s broader efforts to alleviate housing shortages and address other concerns. This post outlines current Contra Costa ADU requirements as of 2023-24, but it is important to stay informed of new developments.

    What Are Contra Costa’s Local Ordinances For ADU Requirements?

    As a top team of real estate professionals in Contra Costa, we have a finger on the pulse of the latest developments in Contra Costa. ADU requirements have undergone significant change recently, which is likely to shake up the housing market all around California. Here are some legislative updates that are making waves:

    • AB 2221: This aims to ease the process of building ADUs. It streamlines the permitting process and allows for the creation of JADUs which have fewer requirements and regulations.
    • SB 897: This alters the restrictions on ADU size, with a maximum size limit of 1,500 square feet. Currently, Contra Costa sets the maximum at the previous limit of 1,200, so keep an eye on potential changes.
    • AB 916: This allows for financial incentives for homeowners to build ADUs.
    • AB 157: The bill that allows for ‘parking-free’ ADUs, eliminating one of the most common barriers to permit approval.

    With all this and more to navigate, it helps to have a professional team with local expertise in your corner. We specialize in helping people buy and sell properties, and can assist you with the planning, construction, and selling/renting of ADUs on your lot.


    What Qualifies As An ADU In Contra Costa?

    According to Contra Costa ADU requirements, an accessory dwelling unit is a secondary residential unit on a single-family property that functions as a complete and independent dwelling. It must include a kitchen and bathroom, have all the necessary utilities built-in, and serve as a supplementary living space. There are various zoning restrictions and building regulations that apply, but they can now provide extra housing options.

    The Contra Costa market for ADUs has had a number of recent legislative changes to address long standing problems. In addition to the ones listed in the previous section, these include:

    • SB 13: Addressing problematic barriers to ADU development, including prohibitive parking regulations, ADU construction fees, and approval timeframes.
    • AB 68: A bill that allows for more than one ADU on a single-family lot, and also reduces lot size requirements for ADUs in California.
    • AB 881: This bill covers several areas relating to ADU construction, including height limitations and setback standards.

    If you plan to build an ADU as a homeowner or developer in Contra Costa, ADU requirements are a key consideration. Be sure to update your knowledge on all the latest legislation to ensure your project goes ahead smoothly. We can help with this.

    The Contra Costa ADU And Zoning Laws

    In accordance with the new regulations, Contra Costa ADU requirements with regards to zoning are set to change in line with the new rules. For a start, you will be able to add 2 more units to your lot, if there is sufficient space. Under AB 68, municipalities are required to approve an ADU up to 1,200 square feet and a JADU up to a maximum of 500 square feet. For multi-family lots, up to 2 detached ADUs will be permitted, as well as multiple ADUs attached to the existing multifamily structures.

    There are also relaxed requirements regarding ADU size, lots, and setbacks. The maximum ADU size imposed by a municipality cannot be less than 800 square feet, 16 feet in height, and with a 4-foot rear and side yard setback. Contra Costa will allow a maximum size of 1,200 square feet, though this could increase so keep an eye on announcements. If you plan to rent out your ADU as a separate condo in Contra Costa, contact us for advice and assistance in making it happen.

    How To Build An ADU In Contra Costa Following All The Requirements

    The permitting process has now been simplified in the Contra Costa ADU requirements. With a relaxing of restrictions on size and zoning, and the effective removal of various barriers like front setbacks and off-street parking, creating a compliant plan is now much simpler.

    Work with local planning departments to be clear on your requirements and you should be able to create a proposal with a high chance of success. Once your application is submitted, the 60-day approval/denial window still stands, but cities are required to be more transparent about the process and give detailed reasons for a refusal, along with recommendations for success.

    Your budget is another key aspect of the process. There are fees for obtaining a permit, and the costs associated with building the ADU depend on the nature of your plans. There may be some financial incentives in your region, so be sure to explore this with your local authority.

    Explore financing options if you don’t have the capital available to cover the entire cost of the project. There are many options available to you, and it can be a sound investment if you are looking to rent or sell your ADU once it is complete.


    Reduced Parking Requirements For ADUs

    Cities and counties are now prohibited from requiring off-street parking for prefabricated ADUs that are:

    • Within a half-mile of public transportation
    • Situated in historic districts
    • An essential part of the main house or a pre-existing ancillary structure

    In the past, parking restrictions have been a significant barrier to securing permits for ADU construction. The easing of these Contra Costa ADU requirements will make it much easier to create compliant plans and get approval for your ADU. This is sure to make a big impact on the housing market in Richmond and beyond, addressing one of the major bones of contention for people looking to build ADUs on their property.

    Frequently Asked Questions

    Can You Build An ADU Before The Main House In California?

    In theory, it is possible. But there are many legal and practical considerations that make it far more challenging than it is to build the ADU after the main house.

    Can I Build An ADU On My Property In California?

    If you own a property in California and have the space and budget to do so, you can build an ADU. But you will have to obtain a permit to do this, which means demonstrating that your plans align with local regulations and legislation.

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