Key Takeaways
- No state bedroom limit: California law doesn’t cap the number of bedrooms in an ADU—it’s based on size and layout.
- Size impacts bedrooms: ADUs can be up to 850 sq ft for 1 bedroom and up to 1,200 sq ft for 2+ bedrooms, affecting how many bedrooms fit comfortably.
- Each bedroom must meet minimums: Bedrooms must be at least 70 sq ft; shared bedrooms require 50 sq ft per person.
- Local rules vary: Cities can set different size, height, and setback rules that impact how many bedrooms are feasible.
What is an ADU?Â
An Accessory Dwelling Unit (ADU) is a living space that shares a lot with a primary dwelling but functions independently, containing a kitchen, a bathroom, and a separate entrance.
ADUs can be attached to the primary house, or they can be completely detached as standalone structures. Many homeowners choose to convert existing secondary structures like garages or basements into ADUs.
Why ADUs are important in California?
California has recognized ADUs as a valuable solution for increasing affordable housing and addressing the state’s housing crisis, leading to the enactment of laws to simplify their construction.
These units offer affordable and functional places to live, helping to meet housing demands.
Are There Limits on Bedrooms in an ADU?
California law does not set a maximum number of bedrooms. California state law does not impose a legal maximum on the number of bedrooms within an Accessory Dwelling Unit.
Instead, the practical number of bedrooms an ADU can have is determined by its overall size limits and specific layout requirements.
How overall size limits and layout rules affect bedroom count. The size of an ADU, dictated by state and local regulations, indirectly influences how many bedrooms can comfortably fit while maintaining a comfortable living space
Size Restrictions That Affect Bedroom Count
Maximum square footage for ADUs. California law allows for a maximum ADU size of 1,200 square feet, though local laws may differ
One-bedroom ADUs: Up to about 850 square feet. The maximum size for an ADU with a studio or one bedroom is 850 square feet.
One-bedroom ADUs typically range from 500 to 850 square feet.
ADUs with two or more bedrooms: Up to 1,000–1,200 square feet. For an ADU with two or more bedrooms, the maximum size is 1,000 square feet.
Detached ADUs can offer flexibility in size, allowing homeowners to build these standalone units up to 1,200 square feet. Generally, two-bedroom ADUs start at approximately 750 square feet and can go up to 1,000 square feet. Three-bedroom ADUs are less common but can exist, particularly on larger lots, and are typically at least 1,200 square feet.
Minimum bedroom size requirements.
At least 70 square feet per bedroom. Each bedroom needs to be at least 70 square feet according to California’s Health and Safety Code
Shared bedrooms: 50 square feet per person. For shared bedrooms, there must be 50 square feet per person
Bedroom Size and Layout Rules
Minimum room dimensions for comfort. While specific overall minimum room dimensions for comfort beyond bedroom size are not explicitly detailed for ADUs in the provided documents, the requirement for ADUs to contain a kitchen, bathroom, and separate entrance implies necessary space allocation for these components.
How space for the kitchen and bathroom affects the number of bedrooms. The allocation of space for essential facilities like a kitchen and bathroom within the overall square footage of an ADU directly impacts the remaining area available for bedrooms.
A Junior Accessory Dwelling Unit (JADU) must include an efficiency kitchen with appliances, a food preparation counter, and storage cabinets of reasonable size, and may include separate sanitation facilities or share them with the primary dwelling, which affects the internal layout and potential for bedrooms.
Local Regulations Affecting ADU Size and Bedrooms
Variations in local zoning and ordinances. While state laws provide baseline standards, local governments in California can adopt their own ADU ordinances, which may introduce different regulations and zoning standards.
These local rules can impact maximum ADU size, height limits, and setback requirements. For example, local jurisdictions in areas like San Diego, Coronado, and La Mesa may have specific ADU codes that differ from state law.
Layout restrictions such as setbacks, height limits, and design rules. California state law mandates a standard 4-foot side and rear yard setback for ADUs.
However, these setbacks can vary based on lot size and local zoning codes. Height limits are generally restricted to 16 feet for an ADU in California. This height can increase to 18 feet if the ADU is within half a mile of a major transit stop or high-quality transit corridor. In San Diego, homeowners may be permitted to build two-story ADUs if specific zoning and setback requirements are met.
Examples of local differences.
Covina: In Covina, the maximum size of an ADU is 850 square feet for a studio or one-bedroom unit and 1,000 square feet for an ADU with two or more bedrooms.
Detached new construction ADUs on single-family lots cannot exceed 800 square feet and a height of 16 feet, maintaining at least a four-foot rear and side yard setback.
San Diego: In San Diego, homeowners with single-family properties can build ADUs up to two stories, provided they meet specific zoning and setback requirements, which can be advantageous for limited sites.
Menlo Park: An ADU may not exceed 16 feet in height and is exempt from the daylight plan requirement applicable to the primary dwelling.
Planning Your ADU Bedroom Count
Factors to consider when choosing the number of bedrooms.
Available space on your property. The space available on the property, considering setbacks and other spatial requirements, is a primary determinant of what can be built
Intended use of the ADU (rental, guest accommodation, etc.). The purpose of the ADU plays a crucial role; for instance, a two-bedroom layout is often considered optimal for rental properties, while a guest accommodation might only require one bedroom
Future needs and comfort. Thoughtful planning for future needs, such as accommodating a growing family or aging relatives, is important.
Strategic bedroom layouts within permitted sizes can create flexible ADUs that appeal to diverse tenant needs, from singles to families.
Balancing bedroom count with overall living space. Efficient use of space is key, and homeowners can maximize living space through open floor plans that merge kitchen and living areas while keeping bedrooms private.
Creating flexible spaces can accommodate different tenant needs.
When maximizing bedrooms may not be the best option. While more bedrooms can increase potential rental income, it is essential to balance the number of bedrooms with overall comfort and functionality.
Smaller ADUs, like studios or one-bedroom units, can be sufficient for a single occupant or a couple. Additionally, impact fees do not apply to an ADU less than 750 square feet in size. For ADUs 750 square feet or larger, impact fees are charged proportionally to the square footage of the primary dwelling unit.
Summary and Next Steps
Recap of key points: no state bedroom limit, size restrictions, and local rules. California law does not impose a direct limit on the number of bedrooms an ADU can have.
Instead, the practical number of bedrooms is influenced by state-mandated size limits and local ordinances. A studio or one-bedroom ADU can be up to 850 square feet, while an ADU with two or more bedrooms can be up to 1,000 square feet, though general state law allows up to 1,200 square feet. Each bedroom must be at least 70 square feet, and shared bedrooms require 50 square feet per person. Local regulations, including setbacks (typically 4 feet from side and rear property lines) and height limits (generally 16 feet), also play a significant role in determining the buildable area and thus the potential number of bedrooms.
Encouragement to consult local authorities and professionals for personalized advice. Homeowners should always check local codes as there can be additional restrictions or allowances beyond state guidelines.
Consulting with local building departments and officials can provide detailed information on specific size limits, design standards, and permitting processes applicable to a particular area
Frequently Asked Questions (FAQs)
Does California law limit the number of bedrooms an ADU can have?
No, California state law does not set a maximum number of bedrooms for an ADU. The number of bedrooms is instead determined by the ADU’s overall size limits and design.
How big can a one-bedroom ADU be in California?
A one-bedroom ADU can typically be built up to 850 square feet in California.
What is the maximum size for an ADU with two or more bedrooms?
An ADU with two or more bedrooms can be up to 1,000 square feet, and detached ADUs can go up to 1,200 square feet in many areas.
Are there minimum size requirements for bedrooms in an ADU?
Yes, each bedroom in an ADU must be at least 70 square feet. If the bedroom is shared, there must be at least 50 square feet of space per person.
How do local rules affect the number of bedrooms I can have in my ADU?
While state law sets the basic rules, local cities and counties can have their own specific rules about ADU size, height, and how close it can be to property lines (setbacks). These local rules can limit the total space available, which then affects how many bedrooms you can fit. Always check with your local planning department for exact rules.
Planning to build an ADU?
Make informed decisions by exploring more essential guides:
How Long Does it Take to Build an Accessory Dwelling Unit (ADU)
How Much Does it Cost to Build an ADU
How Much is a Permit to Build an ADU in California?
How to Get an ADU Permit in California
What is a State Exempt from ADU?
Can My ADU Be Bigger Than My House?
How Much Value Does an ADU Add to a Property in California?
Get the facts you need before starting your project.
