Except as hereinafter provided, this Bylaw shall not apply to structures or uses lawfully in existence or lawfully begun, or to a building or special permit issued before the date of the first publication of notice of the public hearing of such Bylaw required by MGL c. 40A, § 5.

Pre-existing, nonconforming structures or uses may be extended, altered, changed or rebuilt only by special permit from the Board of Appeals and subject to the provisions of § 145-65F. Any such rebuilding, change, extension or alteration shall not be more detrimental than the existing nonconforming use to the neighborhood. Exempted from the requirement for a special permit are the following:

Any nonconforming use or structure which has been abandoned or discontinued for two years or more loses the protection of § 145-17 and shall be required to conform to the current Bylaw.

Construction or operation under a building permit or special permit must conform to any subsequent amendments of the Zoning Bylaw unless the use or construction is commenced within a period of six months after the issuance of the permit and in cases involving construction, unless such construction is continued through to completion continuously and expeditiously.

Setback requirements for the construction of any accessory structure or addition to an existing dwelling need only conform to the Zoning Bylaw requirements in existence at the time of issuance of the original building permit. For structures in existence prior to the Zoning Bylaw refer to § 145-18.