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New Attached Accessory Dwelling Unit Law to Go Into Effect in April

A free-standing accessory dwelling unit

Legislation allowing the conditional use of attached accessory units in the City of Rockville will go into effect Tuesday, April 9, following passage of a zoning text amendment by the Mayor and Council in October. 

Attached accessory dwelling units, or attached ADUs, are secondary dwellings either inside, or attached to, single-family homes. Examples of these include an apartment in a basement or over an attached garage. However, an ADU in a small structure on a foundation in the backyard is not currently permitted and will be subject of future legislation to be considered by the Mayor and Council. 

A property owner who wants to construct an attached ADU must meet requirements for owner occupancy, square footage, parking and other conditions. 

When the new regulations become law in April, those who wish to either build an attached ADU under the new zoning rules or bring an existing unpermitted attached ADU into compliance can begin the application process. Attached ADUs were previously only permitted as special exceptions. 

For more information about attached accessory buildings and dwellings, visit

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