(11)   Accessory Dwelling Units.
(a)   Purpose.
(.1)   Accessory dwelling units help advance City policies by:
(.a)   accommodating new housing units while preserving the character of existing neighborhoods;
(.b)   allowing efficient use of the City's existing housing stock and infrastructure;
(.c)   providing housing options and choices that respond to varying income levels, changing household sizes and lifestyle needs;
(.d)   providing a means for residents – particularly seniors, single parents, and empty-nesters – to remain in their homes and neighborhoods, and obtain extra income, security, companionship, and assistance; and
(.e)   accommodating a broader range of accessible and more affordable housing.
(.2)   The accessory dwelling unit regulations of this section are intended to help promote the benefits of accessory dwelling units, while also preserving neighborhood character and promoting predictability and certainty for established neighborhoods.
(b)   General.
Accessory dwelling units are subject to all applicable regulations of the zoning district in which they are located, except as otherwise expressly stated in this section.
(c)   Where Allowed. 549
Accessory dwelling units are allowed only on lots occupied by a single-family use contained in a detached or semi-detached building in the permitted areas described in § 14-604(11)(d) (Permitted Areas), except within historic structures (as described in subsection (d)(.1) below), where accessory dwelling units are also permitted on lots occupied by a single-family use contained in an attached building. Accessory dwelling units must be located within the interior of the principal building or within the interior of a detached accessory building, such as detached garages, that are in existence as of the effective date of this Zoning Code.
(d)   Permitted Areas. 550
(.1)   Historic Structures.
Accessory Dwelling Units are permitted within any building or structure that, pursuant to Chapter 14-1000, has been designated as historic; or that is located in a district that has been designated as historic and that contributes, in the Historical Commission's opinion, to the character of such district.
(.2)   Large Lots in the RSA-5 and CMX-1 Districts. 550.1
In the RSA-5 and CMX-1 districts, an accessory dwelling unit is permitted, provided that:
(.a)   The area of the lot is a minimum of 1,600 sq. ft.; and
(.b)   No more than one dwelling unit is otherwise permitted.
(e)   Owner Occupancy.
The principal dwelling unit or the accessory dwelling unit must be occupied by the owner of the subject lot. Before final occupancy of the accessory dwelling unit, the property owner shall record an affidavit and deed restriction, stating that the property owner will reside on the property, in either the principal or accessory dwelling unit. Once recorded, the deed restriction (requiring owner occupancy) may not be removed or modified without Zoning Board approval.
(f)   Number.
No more than one accessory dwelling unit is allowed per lot.
(g)   Density (Minimum Lot Area per Unit).
No additional land area is required for the accessory dwelling unit beyond the minimum lot size required in the subject zoning district.
(h)   Location of Entrances. 550.2
Only one entrance to a building containing an accessory dwelling unit may be located on the front facade that faces a street, unless the building contained an additional street-facing entrance before the accessory dwelling unit was created.
(i)   Size. 551
The floor area of an accessory dwelling unit may not exceed 800 sq. ft., except in historic structures (as described in subsection (d)(.1) above).



   Amended, Bill No. 190612 (approved November 6, 2019), effective January 1, 2020.
   Amended, Bill No. 190612 (approved November 6, 2019), effective January 1, 2020.
   Added, Bill No. 210078-A (approved April 28, 2021).
   Amended, Bill No. 210075 (approved March 29, 2021).
   Amended, Bill No. 190612 (approved November 6, 2019), effective January 1, 2020.