Construction or operations under a building or special permit shall conform to any subsequent provision of this Zoning Bylaw, or any amendment thereto, unless the use or construction is commenced within a period of not more than six months after the issuance of the building or special permit and, in cases involving construction, unless such construction is continued through to completion as continuously and expeditiously as is reasonable.

Preexisting nonconforming buildings, structures, or uses may be changed, extended or altered by a special permit issued by the ZBA pursuant to the provisions of § 198-201 and § 198-203 of this Zoning Bylaw, provided that no such change, extension or alteration shall be permitted unless there is also a finding by the ZBA that such change, extension or alteration shall not be substantially more detrimental than the existing nonconforming building, structure or use to the neighborhood; provided, however, that the Planning Board shall serve as the special permit granting authority for changes, extensions and/or alterations to nonconforming buildings, structures, and uses (a) in the Senior and Family Housing Overlay District pursuant to Article 21 of this Zoning Bylaw, and (b) in connection with a site plan approval application to provide outdoor table service at a restaurant pursuant to § 198-1102.1.1.1 of this Zoning Bylaw; and further provided, however, that a single- or two-family dwelling may be changed, extended, or altered so long as the change, extension or alteration does not increase the nonconforming nature of the dwelling. The Building Commissioner shall determine if a change, extension or alteration to a single- or two-family dwelling increases the nonconforming nature of the structure.

Notwithstanding the provisions of § 198-401.1.2, a pre-existing nonconforming use of land that consists of more than six dwelling units for rent on a single lot may not be changed, extended or altered in such a manner that results in either (i) more dwelling units or a greater dwelling unit density on the parcel of land; (ii) an enlargement of any of the dwelling units as measured by its gross floor area or its number of bedrooms or rooms; (iii) the expansion of the use onto adjacent land; or (iv) the subdivision of the lot into more than one lot.

A building for one or two dwelling units may be the subject of alteration, reconstruction, extension or structural change without the necessity of a special permit, provided that the following conditions are met:

Wherever a lawful nonconforming building, structure, or use has been abandoned, or has not been used for two consecutive years or more, it shall not be resumed or reestablished, and all future buildings, structures, and uses shall conform to this Zoning Bylaw.

If a nonconforming building or structure is damaged or destroyed by natural causes or otherwise, then any rebuilding or restoration may take place as of right as long as the rebuilding or restoration conforms precisely in size, location, configuration and extent of use to that which existed prior to the damage or destruction. All rebuilding or restoration shall be commenced within two years of the date of the damage or destruction and shall be continued through to completion as continuously and expeditiously as reasonable. Prior to the expiration of the two years, if the owner applies to the ZBA for an extension of this time period, and if the ZBA finds that there is good cause for the failure to commence rebuilding or restoration, the ZBA may extend the time period for no longer than an additional six months

The ZBA may issue a special permit for any changes in size, location, configuration and extent of use in a nonconforming building or structure damaged or destroyed by natural or other involuntary causes, provided that the ZBA shall find that such changes shall not be substantially more detrimental to the neighborhood than the existing nonconforming use.

Any permitted restoration or rebuilding under § 198-401.1.6 shall commence within six months after the issuance of the special permit therefor and shall continue through to completion as continuously and expeditiously as is reasonable or such permission shall lapse. Prior to the expiration of the six months, if the owner applies to the ZBA for an extension of this time period and if the ZBA finds that there is good cause for the failure to commence rebuilding or restoration, the ZBA may extend the time period for no longer than an additional six months. Unless otherwise authorized by the ZBA, the new or restored building or structure shall have the same height and location on the lot as the replaced structure.

Whenever land is taken by, or conveyed to, a governmental authority having the power of eminent domain or a street is created, widened or relocated, any then existing lot shown on a plan or described in a deed recorded in the Registry of Deeds that conformed to the area and frontage requirements before, but not thereafter, shall be considered to conform, and any existing structure that was in compliance with regulations respecting location before, but not thereafter, shall be considered to be in compliance. This paragraph shall not be applicable if the street was a private way and the land on which it was created, widened or relocated was owned by the owner of the lot or structure affected.

A building, structure, or use existing on January 1, 1947, shall be conclusively presumed to have been in existence before the first publication of notice of the public hearing on the original enactment of this Zoning Bylaw.