What are the requirements to build ADU in Contra Costa?
Building an ADU in Contra Costa enables you to increase your living space and offer affordable housing for adult children transitioning to independent living. For a successful project, understanding Contra Costa's local regulations and thoroughly evaluating the financial aspects of construction are essential. This guide provides comprehensive insights into Contra Costa's ADU regulations and key financial considerations, assisting you in planning and executing your project effectively.
Number of ADUs on a property
How many ADUs can you build in Contra Costa?
In Contra Costa, properties with an existing or proposed single-family home are allowed to construct only 1 ADU.
How many ADUs does Contra Costa allow for multifamily properties?
Multifamily properties can have up to 2 detached ADUs. Additionally, non-livable areas within existing multifamily buildings can be converted to 1 or more ADUs, provided these conversions do not go beyond 25% of the total number of units.
Setbacks for an ADU
What are the setbacks required for an ADU in Contra Costa?
In Contra Costa, ADUs should be setback 4 feet from the side and rear property lines. Front yard setbacks might also apply, but they should allow for the construction of an ADU of at least 800 square feet without significantly impeding ADU development.
What is the minimum distance the ADU must be from existing structures?
Contra Costa does not have a specific requirement for the distance between an ADU and existing buildings. However, it is common in many areas to maintain a separation of about 6 feet.
Are setbacks required if converting existing structures into ADU?
No additional setbacks are required in Contra Costa when converting an existing structure into an ADU.
Find out FREE if the zoning designation for your property allows you to build an ADU
The size of ADU for properties with a single-family home
How big can an attached ADU be in Contra Costa?
An attached ADU in Contra Costa can be up to 50% of the primary unit’s floor area, with a minimum size of 800 square feet. The maximum size is 850 square feet for one bedroom unit, but it can be up to 1,200 square feet if it has two or more bedroom.
How big can a detached ADU be in Contra Costa?
A new detached ADU in Contra Costa can be up to 1,200 square feet in size.
Is there a minimum size of an ADU?
Yes, in Contra Costa, an ADU should be at least 150 square feet, equivalent to an efficiency unit.
Can you convert existing space to an ADU?
Yes, in Contra Costa, existing space within a single-family dwelling can be converted into an ADU.
The size of ADU for properties with a multi-family home
How big can an attached ADU for a multifamily building be in Contra Costa?
In Contra Costa, for a multifamily building, an attached ADU can occupy up to 50% of the primary unit’s floor area, with a minimum size of 800 square feet. For a one-bedroom unit, the maximum size is 850 square feet, while for units with two or more bedrooms, it can be up to 1,200 square feet.
How big can a detached ADU for a multifamily building be in Contra Costa?
A detached ADU for a multifamily building in Contra Costa can be up to 1,200 square feet in size.
Can you stack detached ADUs on top of each other?
Currently, in Contra Costa, there are no explicit regulations addressing the stacking of detached ADUs atop one another.
Can you attach two ADUs to each other?
No, attaching two ADUs to each other is not allowed in Contra Costa. Although they permit up to two separate ADUs on a lot with an existing multifamily dwelling, regulations disallow their attachment.
Can you convert existing space to an ADU?
Yes, in Contra Costa, you have the option to convert existing space within a multifamily dwelling into an ADU.
The height for ADU
What is the max height for an ADU on a property with a single family house?
In Contra Costa, ADUs on properties with a single-family house typically have a height limit of up to 16 feet.
What is the max height for an ADU on a property with a multifamily building?
In Contra Costa, ADUs on properties with multifamily buildings should follow a height requirement of at least 16 feet, aligning the regulations for single-family properties.
Can you build a 2-story ADU in Contra Costa?
Yes, in Contra Costa, you are allowed to build a two-story ADU.
The parking requirements for ADU
What is the parking requirement for an ADU in Contra Costa?
In Contra Costa, the standard parking requirement for an ADU is 1 space per unit or bedroom, whichever is fewer. Nevertheless, there are exceptions, such as for ADUs situated within half a mile of public transit, within architecturally and historically significant historic districts, as part of the proposed or existing primary residence or an accessory structure, when on-street parking permits are not issued to ADU occupants, and when a car share vehicle is accessible within one block of the ADU.
Where can a parking space be located?
In Contra Costa, parking spaces for ADUs are placed in setback areas or arranged in tandem parking configurations, unless certain regional topographical, site conditions, or safety considerations prohibit this. Moreover, if a garage, carport, or covered parking structure is converted into an ADU or demolished for ADU construction, the local authority cannot require the replacement of off-street parking spaces for the primary residence.
Design requirements for ADU
How many bedrooms can an ADU have in Contra Costa?
ADUs in Contra Costa should have at least 1 bedroom, differentiating them from studio units.
Does an ADU need a kitchen in Contra Costa?
Yes, ADUs in Contra Costa should include full kitchens, opposing the efficiency kitchens found in JADUs.
Does an ADU require independent utility meters?
Contra Costa doesn't specify the requirement for separate utility meters for ADUs. For more clarification, it's recommended to inquire with the relevant authorities.
What is the minimum ceiling height?
In Contra Costa, habitable spaces, including ADUs, should comply with the minimum ceiling height of 7 feet, in accordance with the California Building Code.
Get the size of the ADU possible to build on your property after applying all these regulations
Permits for ADU
How long does it take to get an ADU permit in Contra Costa?
The timeframe for processing ADU permit applications in Contra Costa follows state regulations, which allow for up to 2 months.
When do you need a licensed professional to design an ADU in Contra Costa?
It's advisable to involve a licensed professional, such as an architect or engineer, in the ADU design process, especially when considering non-traditional construction methods.
Does Contra Costa require in-person submission of plans for an ADU?
No, physical submission of construction plans and related documents is not required. Instead, all materials should be uploaded electronically through the ePermits center during the submission process.
Does Contra Costa require coastal development permits?
No, in Contra Costa, there is no requirement for obtaining coastal development permits.
Economics of ADU
How much does it cost to build an ADU in Contra Costa?
Constructing an ADU in Contra Costa typically costs around $380 per square foot, which includes expenses for permits, architectural design, and engineering services. For example, building a 900-square-foot ADU would generally cost about $390,000, covering both soft and hard costs.
Is it profitable to build an ADU in Contra Costa?
To assess the financial viability of building an ADU in Contra Costa, it's crucial to compare construction costs with local real estate market values. For instance, a 900-square-foot ADU could be valued at approximately $730,000. Given the construction cost of $390,000, this suggests a potential return on investment of around 88%.
Additionally, profitability considerations may include potential rental income or the benefits of housing family members on the same property.
Can you sell an ADU in Contra Costa?
In Contra Costa, under certain conditions, such as the implementation of statewide regulations like AB 1033, there may be opportunities to sell an ADU or convert it into a condominium. However, this process may require establishing a Homeowner Association (HOA) to manage transactions.
Are ADUs rent controlled in Contra Costa?
No, ADUs in Contra Costa are not subject to rent control regulations. Landlords can annually adjust rents for ADUs under provisions like AB 1482, which primarily apply to properties aged 15 years or older.
How to get money to build an ADU in Contra Costa?
One option for financing ADU construction in Contra Costa is through the CalHFA’s ADU Grant Program, which offers grants of up to $40,000. These funds can be used to cover various expenses, including architectural designs, permits, and site preparation, thereby supporting the development of ADUs as an affordable housing solution in the area.