Southern California homeowners are building ADUs for a mix of reasons. Financially, they can bring in rental income and boost property value. They also address housing needs by creating more affordable units and allowing for multi-generational living. For personal use, ADUs offer flexible space for hobbies, work, or a separate living area. Finally, government incentives like easier permitting make them an attractive option.

ADU is mostly popular with single-family zoned properties.  However, homeowners with R-2 lots may also benefit from the ADU law.  Please click here for more details.

​

No. In fact, the State Legislation prohibits local agencies from including in development standards for ADUs requirements on minimum lot size (CA Gov. Code, § 65852.2, subd. (a)(1)(B)(i)).

General state guideline:

• • Detached ADUs: Up to 1200 sq ft for 2+ bedrooms, 800 sq ft otherwise.

  • Attached ADUs: Limited to 50% of the main residence's square footage.

  • JADUs (converted spaces): Must be under 500 sq ft.
     

Cities and counties can have stricter or looser regulations than the state. Always consult your local planning department for the exact ADU size limits in your area to ensure compliance and a smooth building process.

Please refer to the following guidelines for more details on ADU sizes.  Typically, ADU units are designed between 250 SF to 1,200 SF.  The “automatic” approval mandated by State Law is valid for units with 800 SF or under. The State Legislation prohibits a local agency from establishing a maximum size of an ADU of less than 850 square feet, or 1,000 square feet if the ADU contains more than one bedroom and requires approval of a permit to build an ADU of up to 800 square feet ((CA Gov. Code, § 65852.2, subd. (c)(2)(B) & (C)). A statewide exemption ADU is an ADU of up to 800 square feet, 16 foot in height and with 4-foot side and rear yard setbacks. ADU law requires that no lot coverage, floor area ratio, open space, or minimum lot size will preclude the construction of a statewide exemption ADU.

ADU can be built from ground up in the backyard, either attached or detached from the main house, and it also can be built by converting space within the existing house structure (i.e. garage conversion, den conversion, etc.)

Yes.  ADU law allows the construction of a detached new construction statewide exemption ADU to be combined with a JADU within any zone allowing residential or mixed uses regardless of zoning and development standards imposed in an ordinance.

Homeowners can potentially build an ADU and a JADU depending on the available space within the property.  An ADU can be accomplished by building an extension of the primary dwelling unit or by constructing a new stand-alone unit.  The JADU can be accomplished from converting an existing space within the primary dwelling unit (i.e. garage conversion, living room conversion, etc.).

If an ADU is created through the conversion of a garage, carport or covered parking structure, then replacement of off-street parking spaces cannot be required by the local agency (CA Gov. Code, §65852.2, subd. (a)(1)(D)(xi)).

Yes, it is now possible to sell your ADU (Accessory Dwelling Unit) separately from the main home in California, thanks to the enactment of Assembly Bill 1033 (AB 1033) in October 2023. This legislation allows ADUs to undergo condominium conversion, meaning they can potentially be sold as individual units, similar to condos. However, the ability to sell ADUs separately is subject to local government approval, as AB 1033 gives local jurisdictions the power to decide whether to allow such sales.

No.  ADU laws are considered state laws therefore superseding any local municipality laws including HOA by-laws.  AB 670 provides that covenants, conditions and restrictions (CC&Rs) that either effectively prohibit or unreasonably restrict the construction or use of an ADU or JADU on a lot zoned for single-family residential use are void and unenforceable (CA Civil Code Section 4751).

Yes, it is possible to do so. Check with your local planning department.  A local agency may allow the expansion area of a detached structure being converted into an ADU to have no setbacks, or setbacks of less than four feet, if the existing structure has no setbacks, or has setbacks of less than four feet. A local agency shall not require setbacks of more than four feet for the expanded area of a detached structure being converted into an ADU.

Adding an ADU creates the essence that the single-family residence is turned into a duplex or triplex.  But a duplex (by traditional definition) contains 2 primary dwelling units, whereas ADU is considered an ACCESSORY dwelling unit.

There are many factors that contribute to the cost of building an ADU. The size, design, materials, and location all play a role in determining the final price. In addition, there may be permit fees, labor costs, and other expenses that need to be taken into consideration. Schedule an appointment with us today to discuss your options and get a personalized quote for your specific ADU project.

The fees charged by local municipalities will vary.  Contact the local planning / building department to get the most accurate information.  However, based on the ADU legislation, there is impact fee exemptions for ADU up to 750 square feet (Government Code Section 65852.2, Subdivision (f)(3)).  For ADU larger than 750 square feet, there will be impact fees charged in proportion to the size of the primary dwelling unit (Gov. Code, § 65852.2, subd. (f)(3)).

Absolutely. HELOC (Home Equity Loan), 2nd Mortgage, Personal Loan, or Chisel & Tool proprietary ADU financing. Contact CHISEL & TOOL for a complimentary consultation on your ADU needs.

The approximate time to BUILD an ADU is as follow:

• Conversion: 3 to 6 months 

• Attached: 6 to 9 months 

• Detached: 9 to 12 months 

The above time frame excludes the time to design and to apply for the permits. 

The time frame is also largely affected by size of the ADU.

While the prefab base price might seem cheaper, factor in transportation, on-site foundation works, installation, and utility connections. These can add up. Prefab ADUs also come in standard designs. Extensive customization adds to the cost and might erase the cost advantage. Ultimately, a site-built ADU should be competitive in cost.

Utilities must be separated to electrical, gas, water, and sewer line / drainage line.

Per 2024, most, if not all, of the cities in CA don’t allow gas line into a new construction ADU.

Electrical line can be connected to the existing main house panel assuming there is sufficient power supplied in the existing main panel. Contact us for a consultation since we are a CA licensed electrician.

Water line can be connected to the existing water line. There are times however, that an upgrade in water meter is necessary when an ADU is built. It happens mostly when a fire sprinkler system is required in the ADU.

Yes, newly constructed ADUs in California are generally required to have solar panels according to the California Department of Housing and Community Development's 2020 ADU handbook. This applies to newly constructed, non-manufactured, detached ADUs to be in compliance with California Title 24 Building and Energy Efficiency Standards. However, there are exemptions for ADUs constructed within existing spaces or as additions to existing homes, including detached buildings converted from non-residential to residential space.

You can book a consultation with us to design your ADU and our T24 expert will determine your solar requirements.

It is possible to have a separate mailing address for the ADU.  Please check with the local planning / building department.  Usually, the ADU address would have “½” added to the address. 

Rent control is applicable based on the local municipality where the property is located.  ADU does not affect rent control one way or another.

Property Tax is assessed by an assessor.  Please contact a CPA and/or Attorney for a more accurate information on this matter.  Although, do not miss the bigger picture of building an ADU.  The capital gain obtained by having an ADU should be more than enough to offset any increased in property tax.  ADU is also good for the local community to ease housing constraints. 

Building an ADU can be a significant undertaking, but the potential rewards are substantial.

• Boost your income: Renting out your ADU can bring in a steady stream of income, helping offset your mortgage or providing extra financial security. With housing costs high in California, ADUs are in high demand by renters.

• Increase your property value: Generally, adding a permitted dwelling unit increases the overall value of your property. This can be a great benefit if you decide to sell down the line.

• Multi-generational living: An ADU provides a comfortable space for aging parents, adult children, or other loved ones. You can maintain close relationships while offering them some privacy and independence.

• Flexible use of space: Don't need a rental unit? An ADU can be your dedicated home office, art studio, gym, or hobby room. It frees up space in your main house and creates a dedicated zone for your needs.

• Sustainable investment: ADUs promote efficient land use by maximizing existing space. They also often use prefabricated construction methods, which can reduce waste compared to traditional builds.

• Government support: Many California cities and the state itself are actively encouraging ADU construction. This means easier permitting processes, financial incentives, and streamlined resources to help you through the process. Check with your local department of planning to see what programs are available in your area.