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Home > ADU F.A.Q.


What are ADUs?
An Accessory Dwelling Units (ADUs) is a secondary housing unit on a single-family residential lot. ADU’s are known by many different names: granny flats, in-law units, backyard cottages, secondary units and more. No matter what you call them, ADUs are an innovative and affordable way to add much-needed housing in California.

What are the benefits of ADUs?

  • ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.
  • ADUs can provide a source of income for homeowners.
  • ADUs are built with cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings.
  • ADUs allow extended families to be near one another while maintaining privacy.
  • ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.
  • ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.

What are the new ADU laws?
New law effective January 1, 2019
As of January 1, 2019, homeowners who created accessory dwelling units (ADUs) without the required building permits may have the opportunity to bring their ADUs into compliance. For ADUs that were constructed without building permits, local building officials now have the option to inspect an ADU and apply the building standards that were in effect at the time the unit was constructed. This bill: SB 1226 (Bates), adds Section 17958.12 to the California Health and Safety Code, and with application of appropriate building codes, may allow issuance of a building permit for the residential unit.

Other recent updates to state laws for ADUs
Effective January 1, 2018
The Legislature further updated ADU law effective January 1, 2018, to clarify and improve various provisions in order to promote the development of ADUs. These include allowing ADUs to be built concurrently with a single-family home, opening areas where ADUs can be built to include all zoning districts that allow single-family uses, modifying fees from utilities, such as special districts and water corporations, and reducing parking requirements. Please see the HCD Technical Assistance Memorandum: Accessory Dwelling Unit Legislation (PDF), for more information.

State legislation that took effect January 1, 2017 gave California cities more flexibility and latitude for allowing homeowners to build ADUs. Three separate bills were introduced and signed by Governor Brown; SB 1069 (Wieckowski), AB 2299 (Bloom), and AB 2406 (Thurmond). Each of these land use bills make it easier than ever for homeowners to take advantage of this attractive opportunity.

Why choose Alliance for your ADU?
The many benefits of building an ADU have become very well known, especially since the recent favorable changes to the law (see below for a list that details the benefits of ADU’s in general). In this section, however, we want to emphasize the specific benefits of building a pre-fab ADU with Alliance:

  • Turn Key Experience: Alliance provides everything from start to finish – design, planning, permit submittal, communication with city building department, site preparation, delivery, foundation, set-up, utilities, inspections
  • High Quality, Low Price: Pre-fab housing is built in a controlled environment using high quality building materials. The factories build thousands of units per year, which means they get huge discounts on materials, and their labor force is highly skilled due to the amount of repetition
  • Quick Construction: Even though all of our homes are custom built to order, it only takes between 8-10 weeks for the factory to produce your home once you have selected your design. It takes another 3-6 weeks on-site. In total, you can expect a 3 to 4 month build process with only the last few weeks in your yard. A traditional site-built structure may take longer than a year and your backyard will be a mess the whole time
  • Less Disruptive: Much of the building is done off-site at the factory. We can be in and out of your backyard in as little as 3 weeks
  • Eco Friendly: When building in a controlled environment there is very little wasted material and environmental pollution. In addition, many of our homes are energy star certified which helps to reduce utility bills (low e windows, energy efficient appliances, smart thermostats, sealed duct work, well insulated walls, etc.