What is an Accessory Dwelling Unit (ADU)?

An accessory dwelling unit, also known as an ADU, is a secondary housing unit to a principal single-household dwelling unit in terms of gross floor area, intensity of use, and physical characteristics. An ADU will have kitchen and bath facilities that are separate from the principal dwelling, and it may have a separate entrance.

In Washington, D.C., accessory apartments are permitted only in the following residential zoning districts: R-1-A, R-1-B, R-2, R-3, R-6 through  R-17, and R-21. In R-19 and R-20, a Special Exception is required.

To determine if your property is in one of these residential districts, you can search the interactive DC Official  Zoning Map.

The requirements to convert a portion of the property to an ADU depend on specific variables, such as dwelling/structure type. For more information about ADU conversion requirements, please refer to the Accessory Apartment requirements cheat sheet. This cheat sheet is published by the Department of Consumer and Regulatory Affairs, which used to be the D.C. agency that administers building and land regulation. DCRA has been replaced by the Department of Buildings.



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