In this subtitle the following words have the meanings indicated. “Accessory dwelling unit” means a secondary dwelling unit that is: on the same lot, parcel, or tract as a primary single–family detached dwelling unit; and not greater than 75% of the size of and subordinate in use to the primary single–family detached dwelling unit. “Accessory dwelling unit” includes a structure that is: separate from the primary single–family detached dwelling unit; or attached as an addition to the primary single–family detached dwelling unit. “Dwelling unit” means a single unit providing complete living facilities for at least one individual, including, at a minimum, provisions for sanitation, cooking, eating, and sleeping. “Dwelling unit” does not include a unit in a multifamily residential building. “Utility” means water or sewer disposal services provided by: a private company regulated under Division I of the Public Utilities Article; the Washington Suburban Sanitary Commission regulated under Division II of the Public Utilities Article; a sanitary commission regulated under Title 9, Subtitle 6 of the Environment Article; or a municipal authority regulated under Title 9, Subtitle 7 of the Environment Article.

This subtitle applies only to the development of accessory dwelling units on land with a single–family detached dwelling unit as the primary dwelling unit.

It is the policy of the State to promote and encourage the creation of accessory dwelling units on land with a single–family detached dwelling unit as the primary dwelling unit in order to meet the housing needs of the citizens of Maryland. Except as provided in this subtitle and subject to paragraph (2) of this subsection, this subtitle does not alter or abrogate any zoning power or related authority granted to a local jurisdiction under this title. Local jurisdictions shall establish policies that further the intent of this subtitle.

On or before October 1, 2026, each legislative body shall adopt a local law authorizing the development of accessory dwelling units in accordance with this section. A legislative body may adopt a local law that: establishes standards for accessory dwelling unit safety; and prohibits the full or partial conversion of an accessory structure as an accessory dwelling unit if the only vehicular access to the accessory structure is from an alley. A local law adopted under this section shall provide for construction of accessory dwelling units that meet public health, safety, and welfare standards, including relevant building codes and adequate public facilities provisions. A local law adopted under this section shall exclude the development of an accessory dwelling unit from the calculation of density and the application of any measures limiting residential growth that pertain to the lot, parcel, or tract proposed for the development of the accessory dwelling unit. A local law adopted under this section may not establish setback requirements that exceed the existing accessory structure setback requirements from the side and rear lot lines. A local law adopted under this section may establish additional off–street parking requirements that consider: the cost to construct off–street parking spaces; whether sufficient curb area exists along the front line of the property to accommodate on–street parking; the increase in impervious surface due to the creation of new off–street parking and the relation to any applicable stormwater management plans; and variability due to the size of the lot, parcel, or tract on which the accessory dwelling unit or primary dwelling is located. A local law adopted under this paragraph shall provide for a waiver process from the parking requirements. Before adopting a local law under paragraph (1) of this subsection, a legislative body shall complete a parking study to determine the applicable needs and restrictions in the jurisdiction.