SECTION 5. Section 3 of said chapter 40A of the General Laws, as appearing in the 2014 Official Edition, is hereby amended by adding the following paragraphs:-

No zoning ordinance or by-law shall prohibit or require a special permit for the use of land or structures for an accessory dwelling unit or the rental thereof in a single-family residential zoning district on a lot with 5,000 square feet or more or on a lot of sufficient area to meet the requirements of title 5 of the state environmental code established by section 13 of chapter 21A, if applicable, that is occupied by the owner, so long as that unit or the principal dwelling is occupied by at least one person with disabilities or who is elderly.  Such land or structures may be subject to reasonable regulations concerning dimensional setbacks and the bulk and height of structures. The zoning ordinance or by-law may require that the principal dwelling or the accessory dwelling unit be owner-occupied and may limit the total number of accessory dwelling units in the municipality to a percentage not lower than 5 percent of the total non-seasonal housing units in the municipality. Not more than 1 additional parking space shall be required for an accessory dwelling unit but, if parking is required for the principal dwelling, that parking shall either be retained or replaced.  As used in this paragraph, “accessory dwelling unit” shall mean a self-contained housing unit, inclusive of sleeping, cooking and sanitary facilities, incorporated within the same structure as the principal dwelling or in a detached accessory structure and that: (i) is located on the same lot as the principal dwelling; (ii) maintains a separate entrance, either directly from the outside or through an entry hall or corridor shared with the principal dwelling; (iii) shall not be sold separately from the principal dwelling; (iv) is not smaller in floor area than 450 square feet; (v) may include up to two bedrooms; and (vi) is not larger in floor area than ½ the floor area of the principal dwelling or 900 square feet, whichever is smaller.  An accessory dwelling unit allowed under this paragraph is considered owner-occupied upon transfer of title of the principal dwelling in whole or in part to a trust in which at least one beneficiary is a person with disabilities or an elderly person, so long as some part of the dwelling is occupied by a person with disabilities or an elderly person. Nothing in this paragraph shall authorize an accessory dwelling unit to violate the building, fire, health or sanitary codes or wetlands laws, ordinances or by-laws.

When used in this section, the term “person with disabilities” means a person who has been determined to be disabled (i) in accordance with criteria established by local bylaw or ordinance, if any, or (ii) by the Social Security Administration or MassHealth, notwithstanding any local bylaw or ordinance; and “elderly” means sixty-five years of age or older.