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ADU Regulations, Permitting, and Fees

An ADU is accessory to a primary residence and has a complete independent living facility for one or more persons.
A Junior Accessory Dwelling Unit or JADU is a unit that is no more than 500 square feet in size and contained entirely within a single-family residence.

Single Family Home

One ADU and one JADU are permitted per lot within the proposed space of a
single-family dwelling or existing space of a single-family dwelling or accessory structure that meets specified requirements such as exterior access and setbacks for fire and safety.

Multi-Family Home

Under subdivision (e), an applicant may apply to build up to two detached ADUs and at least one interior ADU up to 25 percent of the number of units in the proposed or existing multifamily dwelling. All interior ADUs, however, must be converted from non livable space, which is not a requirement under subdivision (a) for ADUs associated with single-family sites. It should also be noted that if there is no existing non-livable space within a multifamily structure, an applicant would not be able to build an interior ADU under subdivision (e). Attached ADUs are also prohibited under this subdivision.

A local government may, by ordinance, establish minimum and maximum unit size requirements for both attached and detached ADUs; however, maximum unit size requirements must allow an ADU of at least 850 square feet, or 1,000 square feet for ADUs with more than one bedroom. For local agencies without an ADU ordinance, maximum unit sizes are 1,200 square feet for a new detached ADU and up to 50 percent of the floor area of the existing primary dwelling for an attached ADU (at least 800 square feet).
There is no height limit contained in State ADU Law, but local agencies may impose height limits provided that the limit is no less than 16 feet.

A setback of no more than four feet from the side and rear lot lines shall be required for an attached or detached ADU. However, setbacks should not unduly constrain the creation of ADUs and cannot be required for ADUs that fall under subdivision (e).

No setback shall be required for an ADU created within an existing living area or
accessory structure or an ADU created in a new structure in the same location as an existing structure, while not exceeding the existing dimensions, including height.

A local agency may still apply front yard setbacks for ADUs, but front yard setbacks cannot preclude an ADU of at least 800 square feet

  • One ADU and one JADU are permitted per lot within the proposed space of a single-family dwelling or existing space of a single-family dwelling or accessory
    structure that meets specified requirements such as exterior access and setbacks for fire and safety.
  • One detached new construction ADU that does not exceed four-foot side and rear yard setbacks. This ADU may be combined on the same lot with a JADU, and may be required to meet a maximum unit size requirement of 800 square feet and a height limitation of 16 feet.
  • Multiple ADUs within the portions of multifamily structures that are not used as livable space. Local agencies must allow at least one of these types of ADUs and up to 25 percent of the existing multifamily structures.
  • Up to two detached ADUs on a lot that has existing multifamily dwellings that are subject to height limits of 16 feet and four-foot rear and side yard setbacks.
Since our ADUs are inspected at the factory, the building inspectors cannot inspect the ADU itself. The only inspections necessary on your property are for the site work: foundation, utilities, stairs, etc.
It depends on your local jurisdiction and the scope of work. Timelines can range anywhere from 2 months to 12 months, depending on permitting speed, utility coordination, and site conditions. On average, most of our projects are completed in about 4 to 6 months from start to finish.

No. Prior to recent legislation, ADU laws allowed local agencies to elect whether the primary dwelling or ADU was required to be occupied by an owner. The updates to State ADU Law removed the owner-occupancy requirement for newly created ADUs effective
January 1, 2020. The new owner-occupancy exclusion is set to expire on December 31, 2024; however, local agencies may not retroactively require owner-occupancy for ADUs permitted between January 1, 2020, and December 31, 2024.

However, should a property have both an ADU and JADU, JADU law requires owner-occupancy of either the newly created JADU or the single-family residence. Under this specific circumstance, a lot with an ADU would be subject to owner-occupancy requirements.

Yes. Local agencies may require that the property be used for rentals of terms longer than 30 days.

Yes. Since our ADUs are federally approved, once they are fixed to a foundation it will be considered “real property” or “real estate.” This differs from “personal property” in that it will stay with the property and allows for the increase in your home’s value.

Construction

“Prefab” is short for prefabricated. A prefab ADU is one constructed in a factory.

Our ADUs are manufactured homes, built to strict HUD (federal) construction and safety standards inside a certified factory. Once completed, they’re transported to your property and installed on a permanent foundation—just like a site-built home.

Manufactured ADUs offer the same quality, energy efficiency, and longevity as modular or site-built structures, but are more affordable and faster to install because the entire home is built indoors under consistent quality control.

We use two main types of foundations depending on the project site and customer preference:

Concrete Stem Wall Foundation
A concrete stem wall foundation is a permanent, site-built foundation that supports the home on continuous concrete walls around the perimeter. It’s similar to a small crawl-space foundation and is typically used when the site needs additional elevation, leveling, or a more traditional appearance. Stem walls provide excellent durability, allow for under-floor access, and are ideal for sloped lots or when local building departments require a full perimeter foundation.

PowerFrame Seismic Pier Foundation
The PowerFrame system is a pre-engineered steel chassis foundation designed specifically for prefab and modular ADUs. It uses anchored steel piers, cross-bracing, and seismic tie-downs to secure the home to the ground, meeting all California Title 25 and CBC seismic and wind-load requirements. This system provides the same structural stability and code compliance as a concrete foundation but installs faster, requires less excavation, and allows easier access to utilities underneath the home.

Both options are permanent foundations approved for ADUs in California—we help determine which is best based on your site conditions, cost, and local code requirements.

Water, gas, and electricity can be pulled from the main home and the sewer line must be connected to your home’s main sewer lateral. In some cases, it can be cheaper to drop a new electrical service from a PG&E pole. Our team will always find the most cost-effective solution.

Absolutely! We can order the unit to be built all electric. If you choose to go all electric, your ADU will need to have a 200 amp service.

Although it is not required to install solar on a prefabricated ADU that meets Title 25 standards, we can order your ADU solar-ready.

Our ADUs are built using traditional building materials and construction methods, but done in an efficient assembly line. These ADUs are built to Housing and Community Development (HCD) standards and must pass inspection in order to reach your property.

Our delivery team will transport the ADU from the factory to the front of your property. From there, our installation team will either crane the unit onto the foundation or roll the unit onto the foundation if your yard allows for it.

Installation of fire sprinklers may not be required in ADUs (attached, detached, or
conversion) where sprinklers were not required by building codes for the existing primary residence.

No. Assembly Bill 670 (2019) and AB 3182 (2020) amended Section 4751, 4740, and 4741 of the Civil Code to preclude common interest developments from prohibiting

OR

unreasonably restricting the construction or use, including the renting or leasing of, an ADU on a lot zoned for single-family residential use. Covenants, conditions and restrictions (CC&Rs) that either effectively prohibit or unreasonably restrict the construction or use of an ADU or JADU on such lots are void and unenforceable or may be liable for actual damages and payment of a civil penalty. Applicants who encounter issues with creating ADUs or JADUs within CC&Rs are encouraged to reach out to HCD for additional guidance.

Design

For a comprehensive list of options, please contact our team here.

Absolutely! To find a comprehensive list of upgrades, please contact our team here.

Yes, we can make certain modifications to our floor plans. Some common modifications we make are expanding/shrinking the length and/or width of the ADU as well as individual rooms. Please contact us for more information.

Finances

Our starting project price is based on a standard ADU project. The project price may increase due to many various factors, but here are some of the more common ones we come across:
-Desired ADU location is set behind a home with no access so a crane is necessary for installation
-Desired ADU location is 120+ feet from the driveway/street
-Your main home’s panel needs to be upgraded to accommodate the new ADU
-Demolition/Tree removal
-Retaining walls are necessary due to a sloped yard
-Fire sprinklers in the ADU are required by local jurisdiction
-Sewer injector pump is needed since there is not enough slope to main sewer lateral

The increase in home value will be based on comparable homes with ADUs in your surrounding area. Our partners at Renofi.com find that adding a detached ADU can result in a 60-70% ROI.

The average rent per square foot in the Bay Area is $3-$4. To find a better estimation, you can search for ADU rentals with comparable size in your surrounding area.

The most commonly used options are cash-out refinances, renovation loans, savings, personal loans, and construction loans. You can our finance page or contact us for more information.

Effective September 20, 2021, the California Housing Finance Agency’s (CalHFA) ADU Grant Program provides up to $40,000 in assistance to reimburse qualifying homeowners for predevelopment costs necessary to build and occupy an ADU or JADU on a lot with a single-family dwelling unit. The ADU Grant Program is intended to create more housing units in California by providing a grant to reimburse qualifying homeowners for predevelopment costs. Predevelopment costs include, but are not limited to, architectural designs, permits, soil tests, impact fees, property surveys, and energy reports. For additional information or questions, please see CalHFA’s ADU Grant Program at https://www.calhfa.ca.gov/adu or contact the CalHFA Single Family Lending Division at (916) 326-8033 or SFLending@calhfa.ca.gov.

A blended assessment will take place. This means that your entire property will not be reassessed, rather, the assessor will add the current market value of your ADU to your home’s value.