If you’re a homeowner in California, you may be wondering how many accessory dwelling units (ADUs) you can build on your property. An ADU is a housing unit with complete independent living facilities located on the same piece of property as another home. ADUs can be detached, attached, or converted from existing space, and some can be junior accessory dwelling units (JADUs) that are entirely contained in single-family residences.
ADUs are affordable spaces to construct and provide a source of income for homeowners in California, where they’re allowed in zones that allow single-family and multifamily uses. ADUs are also known as second units, in-law units, granny flats, backyard homes, and casitas. ADUs have their own separate addresses and utility meters.
ADU laws in California have been revised to reduce barriers, streamline approval processes, and expand capacity for ADU development. However, there are still some limitations and requirements you need to be aware of before you start planning your ADU project. Below, the pros from Forever Builders, the full home and kitchen remodelers San Diego homeowners trust for exceptional craftsmanship and outstanding service, explain some of the most important factors that determine how many ADUs you can build on your property in California.
Current ADU Laws in California
The current ADU laws in California are based on a series of bills passed by the state legislature in 2019 and 2020. These bills amended the existing state ADU law and made several changes to facilitate ADU development. Some of the key changes included:
- Allowing at least one ADU and one JADU per lot with a proposed or existing single-family dwelling
- Allowing up to two detached ADUs per lot with a proposed or existing multifamily dwelling
- Allowing up to 25 percent of existing multifamily dwelling units to be converted into ADUs within portions of existing structures that aren’t used as livable space
- Prohibiting local agencies from imposing minimum lot size requirements, maximum ADU size requirements of less than 850 square feet for one-bedroom units or 1,000 square feet for two-bedroom units, or parking requirements for ADUs located within half a mile of public transit or within a historic district
- Requiring local agencies to approve or deny an ADU application within 60 days of receiving a completed application
- Limiting impact fees for ADUs under 750 square feet to zero and proportionately reducing impact fees for larger ADUs
These changes apply statewide unless a local agency adopts an ordinance that’s consistent with state ADU law.
Local Zoning Laws
The first thing you need to check is the zoning of your property. Zoning determines what types of uses and structures are allowed on your property. You can find out your zoning by contacting your local planning department or using online tools, such as ZIMAS for Los Angeles or SF Property Information Map for San Francisco.
Generally speaking, ADUs are allowed in zones that allow single-family and multifamily uses. However, some zones may have specific restrictions or conditions for ADU development. For example, some zones may limit the size, height, or design of ADUs, or they may require a minimum lot size or setback for ADUs. Some zones may also prohibit certain types of ADUs, such as detached or attached ADUs.
Number of Existing Units
The number of existing units on your property also affects how many ADUs you can build. According to state law, if you have a single-family home on your property, you can build one detached ADU and one JADU or one attached ADU and one JADU. If you have a multifamily home on your property, you can build up to two detached ADUs or convert up to 25 percent of the existing units into ADUs.
However, some local jurisdictions may have different rules for the number of ADUs allowed on a property. For example, some cities may allow more than one detached ADU on a single-family lot or more than two detached ADUs on a multifamily lot. Some cities may also allow more than one attached ADU on a single-family lot or more than 25 percent of the existing units to be converted into ADUs on a multifamily lot. Therefore, it’s important to check with your local planning department to find out the exact number of ADUs you can build on your property based on your zoning and existing units.
Other Requirements
Besides regulations dealing with zoning and the number of existing units, there are other requirements you need to comply with when building ADUs on your property. These include:
- Parking – State law doesn’t require parking for ADUs located within half a mile of public transit, within an architecturally and historically significant district, within an existing structure or garage conversion, or when there’s a car share vehicle located within one block of the ADU. However, some local jurisdictions may have different parking standards for ADUs that vary by zone or location.
- Owner-occupancy – State law doesn’t require owner-occupancy for ADUs built between 2020 and 2025. However, some local jurisdictions may have owner-occupancy requirements for ADUs built before 2020 or after 2025.
- Impact fees – State law prohibits impact fees for ADUs less than 750 square feet in size. For larger ADUs, impact fees must be proportional to the size of the primary dwelling unit. However, some local jurisdictions may have different fee schedules for ADUs that vary by zone or location.
- Design – State law requires that ADUs comply with the building codes and health and safety standards applicable to dwellings. However, some local jurisdictions may have additional design standards for ADUs that vary by zone or location.
Building ADUs on Your Property
Depending on your property’s zoning and characteristics, you may be able to build one or more of the following types of ADUs:
- Detached ADU – A separate structure from the primary dwelling located on the same lot. Detached ADUs can be new construction or conversions of existing structures, such as garages, sheds, or pool houses.
- Attached ADU – A structure that’s attached to the primary dwelling or shares a common wall with it. Attached ADUs can be new construction or conversions of existing spaces, such as basements, attics, or additions.
- Converted ADU – A portion of an existing single-family or multifamily dwelling that’s converted into an independent living unit. Converted ADUs can be created by partitioning existing space or by converting accessory structures such as garages or storage rooms.
- JADU – A unit that’s no more than 500 square feet in size and is contained entirely within an existing single-family dwelling. A JADU must have a separate entrance from the main entrance to the dwelling and may share sanitation facilities with the existing dwelling.
As you can see, there are many factors that determine how many ADUs you can build on your property in California. The best way to find out is to consult with your local planning department and a professional contractor, who can help you navigate the process and requirements for your specific project.
When you’re ready to add an ADU to your home, make sure to hire the best contractors in the business. The team from Forever Builders are the experts in home renovation San Diego homeowners can trust to provide the most affordable home remodeling services and ensure their visions become reality. From design to completion, we’ll help you create the home you’ve always wanted, meeting all your expectations while keeping your costs within budget. To find out more about our outstanding remodeling services, give one of our friendly team members a call today at (833) 243-5624.