The Boards, in granting special permits and variances, shall ensure that any change or extension of a use, reconstruction, extension or structural change of a structure or any such alteration of a structure as provided above in § 165-87B and C is readily apparent and shall make such information available to the Building Inspector. The Board of Appeals shall annually as of June 1 list which special permits and variances appear to be still in use, which appear to have ceased use during the previous year and which appear to have become invalid by reason of nonuse for two years. This shall be a public record and a copy shall be sent annually to the Selectmen and Building Inspector.

However, this chapter shall not apply where alteration, reconstruction, extension or structural change to a single- or two-family residential structure does not increase the nonconforming nature of said structure, provided that no such extension or alteration shall be permitted unless there is a finding by the Board of Appeals that such change, extension or alteration shall not be substantially more detrimental than the existing nonconforming use to the neighborhood.

The foregoing provisions of § 165-87 relating to nonconforming uses and structures shall not apply to billboards, signs and other advertising devices subject to the provisions of MGL c. 93, §§ 29 through 33, inclusive, and MGL c. 93D.

A lawful nonconforming use shall not be reestablished after being abandoned, but the use of a lawful nonconforming building or structure or premises may be reestablished after not more than two years of continuous nonuse without intent to abandon.

Nothing in this chapter shall be deemed to prohibit or unreasonably regulate the expansion or reconstruction of existing structures thereon for the primary purpose of agriculture, horticulture or floriculture in parcels of more than five acres. For such purpose, land divided by a public or private way or a waterway shall be construed as one parcel.

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

Preexisting nonconforming structures or uses may be extended or altered, provided that no such extension or alteration shall be permitted unless there is a finding by the Board of Appeals in granting a special permit that such change, extension or alteration shall not be substantially more detrimental than the existing nonconforming use to the neighborhood. A special permit shall not be required when alteration, reconstruction, extension or structural change to a single or two family residential structure does not increase the non-conforming nature of said structure.