As California faces a growing housing crisis, Accessory Dwelling Units (ADUs) have become a popular solution for increasing housing density without drastically altering neighborhoods. ADUs, sometimes referred to as “granny flats” or “in-law units,” offer additional living spaces within single-family or multi-family properties. However, if you’re considering adding an ADU to your property, understanding the size limits and regulations that govern ADUs in California is crucial. This article will explore how big an ADU can be in California, considering state and local regulations, as well as the types of ADUs allowed.
What Is an ADU?
Before diving into size specifics, it’s essential to understand what an ADU is. An ADU is a secondary housing unit located on the same lot as a primary residence. These units can either be attached to the main home, detached as a standalone structure, or converted from existing spaces, such as a garage or basement. They offer a flexible solution for property owners who want to accommodate extended family, generate rental income, or increase property value.
The Importance of ADU Size Regulations
ADU size regulations ensure that these units are functional, safe, and integrated into the existing neighborhood without creating overpopulation or resource strain. California has specific laws that set minimum and maximum size requirements for ADUs, but local jurisdictions can impose additional rules. Knowing both state and local regulations is critical when planning to build an ADU.
California State Law on ADU Sizes
According to California state law, ADU size limits depend on whether the unit is attached or detached from the primary residence. Below are the key size regulations:
Detached ADU Size Limits
A detached ADU is a standalone structure on the property, separate from the primary residence. The maximum size of a detached ADU in California is:
- 1,200 square feet regardless of the size of the primary home.
However, many cities allow detached ADUs to exceed 1,200 square feet if local zoning laws permit, but this requires special permission or a variance.
Attached ADU Size Limits
An attached ADU shares at least one wall with the main house. The size limits for attached ADUs are slightly different:
- Up to 50% of the existing primary residence’s square footage, with a maximum of 1,200 square feet.
For example, if your primary home is 2,000 square feet, your attached ADU can be up to 1,000 square feet. But if your home is larger, the ADU’s size cannot exceed 1,200 square feet.
Junior ADUs (JADUs)
A Junior ADU (JADU) is a smaller unit within the existing structure, typically converted from a bedroom or garage. California law allows JADUs with the following limitations:
- Maximum size of 500 square feet.
JADUs often have efficiency kitchens but share a bathroom with the main residence.
Local Zoning and Ordinances
While California has overarching laws governing ADU sizes, local municipalities have the authority to implement more restrictive rules. Some cities and counties may limit ADU size based on factors like:
- Lot size: Larger lots may allow larger ADUs, while smaller lots could have stricter size restrictions.
- Floor Area Ratio (FAR): FAR limits how much of a lot can be covered by structures, which can impact how large your ADU can be.
- Setbacks: Setbacks, which dictate the distance between a structure and the property line, can affect the design and size of your ADU.
For example, Los Angeles has different requirements than San Francisco or San Diego. Therefore, it’s essential to check with your local planning department to understand the specific size limitations and zoning regulations that apply to your property.
Additional Considerations Affecting ADU Size
Height Limits
In addition to square footage, there are height restrictions for ADUs, which can affect the overall size and layout. Most California cities limit ADUs to a height of 16 feet for detached units. However, in some cases, such as in two-story ADU designs, heights can go up to 25 feet or more, depending on the jurisdiction.
Parking Requirements
Parking is another consideration that might indirectly affect the size of your ADU. Many localities have reduced or eliminated parking requirements for ADUs, particularly in areas close to public transportation. However, if parking is required, it could limit the available space for your ADU, impacting its overall size.
Utility Connections
ADUs often require separate utility connections for water, electricity, and sewer. The size of your lot and your ADU could be constrained by the capacity of these services. Consulting with an engineer or contractor early in the planning phase can help ensure your ADU meets local utility standards.
California’s ADU Exemptions for Small Units
California has introduced some size-related exemptions to streamline the approval process for smaller ADUs. Specifically, ADUs under 750 square feet are exempt from certain impact fees, which can save homeowners thousands of dollars in construction costs. This exemption has made smaller ADUs more popular as affordable housing solutions.
How to Maximize Your ADU Space
To make the most of your ADU’s allowable size, consider these design tips:
- Open Floor Plans: Open layouts can make small spaces feel larger and more functional.
- Multi-purpose Rooms: Use furniture and layout strategies that allow rooms to serve multiple purposes, such as a living room that doubles as a guest room.
- Vertical Storage: Maximize vertical space with tall cabinets and shelves, which can reduce clutter and create more usable living space.
- Natural Light: Large windows and skylights can make a small ADU feel much larger and more inviting.
Conclusion
Understanding the size regulations for ADUs in California is essential for property owners looking to add additional living space. The maximum size of an ADU depends on whether it’s attached or detached, with the general limit being 1,200 square feet. Junior ADUs, a smaller option, are capped at 500 square feet. However, local zoning laws may impose additional restrictions or allowances based on lot size, location, and other factors. Always check with your local jurisdiction to ensure your ADU project complies with all relevant rules. Maximizing the design and function of your ADU can make the most of the available space while avoiding unnecessary fees and delays.
By adhering to California’s ADU size laws and planning carefully, homeowners can contribute to the state’s growing need for housing while adding value and flexibility to their property.