ADUs, sometimes called a Second Dwellings, Auxiliary Dwelling Units, Granny Flats, or Mother-in-Law’s Quarters, are a completely self-contained housing unit located on the same lot as another home. ADUs have their own kitchen, bathroom, and living area. ADUs are considered accessory because they are typically smaller than the primary dwelling and are not considered the main use on the lot.
Detached ADUs are backyard cottages detached from any structure on a property. Detached ADUs are great for maintaining privacy for a renter or maintaining an independent lifestyle for families living together on a property. Because these units stand separate from the main house on their own open space, new construction tends to be more straightforward - not dependent on the quality or conditions of the primary dwelling or garage.
Attached ADUs are attached to the main house. Attached ADUs do maximize their lot coverage by eliminating any setback between the granny flat and the main house. They are more like a traditional addition to the existing home but require a separate bathroom, living area and kitchen.
Conversion ADUs are ADUs built into the existing house. Most Conversion ADUs are garage conversions, but other options could be converting a basement, attic, or even a spare bedroom. These are usually the most cost-efficient ways of adding ADU space to a home.
Junior ADUs or JADU
JADUs are smaller ADUs. Most city ordinances do not require impact fees and other building fees if an ADU is 750 square feet or smaller. If there is room on the lot, a homeowner can add an ADU and a JADU under new state law.