Accessory Dwelling Units

Accessory Dwelling Units (ADUs) are self-contained structures that exist on the same lot as a single family home. Throughout the United States, they go by many different names, including “granny flats”, “in-law units”, “secondary houses”, and “laneway houses”, among others. They can either be attached, detached, or internal.

Attached ADUs are typically either spaces above garages or structures that share a common wall with the primary residence. Detached ADUs are entirely separate from the primary residence, and can either be converted detached garages or tiny homes/cottages in the backyards of a property. Interior ADUs can either be converted garages that were already attached to the primary residence, or conversions of the upper floor or basement of the primary residence. (, 2021)

Accessory Dwelling Units are permitted in many cities and counties across the United States. They are typical in single-family zoning districts. Many provisions stipulate that the owner of the primary residence lives on the property, that the lot meets a minimum lot size, and that there is off-street parking.

Accessory Dwelling Units are becoming increasingly popular in states like California, Minnesota, Oregon, and Vermont as ways to create more affordable housing, as well as generating additional income for property owners. (Architectural Digest, 2020)

They are part of a growing hyperlocal zoning movement across the country, where cities and counties are passing legislation to amend zoning codes to allow for ADUs as housing costs continue to rise.

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