An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family residential lot, typically designed to be self-contained with its own entrance, kitchen, bathroom, and living space. ADUs are usually detached from the primary home or are attached as an addition to the main house, but with a separate entrance. ADUs are typically smaller in size than the primary home and are often used as a rental property or as housing for extended family members. ADU permits are normally faster and easier. You can always combine ADU and home extension in one permits. Setback for ADUs are less than Setback for home extension. ADU adds less property taxes than the same area in Home Extension.
A home extension, on the other hand, is an addition to the existing home, usually built to expand the living space or add additional rooms. Home extensions can be constructed as a single-story or multi-story addition, and can be designed to blend in with the existing structure or to create a contrast in architectural style. Unlike ADUs, home extensions are not intended to be self-contained and usually do not have their own entrance or kitchen.
In summary, the key difference between ADUs and home extensions is that ADUs are standalone structures that are designed to be separate living quarters, while home extensions are additions to the existing home intended to expand living space or add rooms. ADUs can be used for rental income or as housing for family members, while home extensions are primarily for the use of the homeowner.