A. 
Except as otherwise provided herein, this By-law shall not apply to structures or uses lawfully in existence or lawfully begun, or to a building permit or special permit issued, before the first publication of notice of the public hearing on this By-law required by G.L. c. 40A, §5. However, this By-law shall apply to the following:
1. 
Any change or substantial extension of the use;
2. 
To a building permit or special permit issued after the first notice of the public hearing;
3. 
To any reconstruction, extension, or structural change of such structure; and
4. 
To any alteration of a structure begun after the first notice of a public hearing to provide for its use in a substantially different purpose or for the same purpose in a substantially different manner or to a substantially greater extent, except where alteration, reconstruction, extension, or a structural change to a one-family or two-family residential structure does not increase the nonconforming nature of said structure.
B. 
Preexisting nonconforming structures or uses may be extended or altered; provided, that no extension or alteration shall be permitted unless there is a finding by the Board of Appeals that the change, extension, or alteration shall not be substantially more detrimental to the neighborhood than the existing nonconforming structure or use. It is the purpose of this By-law to discourage the perpetuity of nonconforming structures and uses whenever possible.
C. 
Construction or operations under a building permit or special permit shall conform to any subsequent amendments of this By-law unless the use or construction is commenced within a period of 12 months after the issuance of the permit and in cases involving construction, unless such construction is continued through to completion continuously and expeditiously as is reasonable.
D. 
Anything to the contrary in this By-law notwithstanding, the residential use of two or more dwellings on a single lot shall be deemed a preexisting nonconforming use if commenced prior to March 25, 1958. This use may only be altered, extended, or modified by special permit pursuant to this section provided the Board of Appeals finds through a preponderance of credible evidence that the use commenced prior to March 25, 1958, and has not been abandoned or not used for a period of two years or more. In approving any alteration, extension, or modification, the Board of Appeals shall require that the number of dwelling units be limited to the same as in existence on March 25, 1958.
E. 
Any residential structure in existence as of January 1, 1970, not protected by this By-law will be deemed to be conforming to the dimensional requirements of this By-law, but any alteration, reconstruction, extension, or structural change shall conform to the current By-law dimensional requirements.
6.2.1 
Single-Family or Two-Family Dwellings.
A. 
Alteration, reconstruction, extension, or structural change to a single- or two-family residential structure that does not increase the nonconforming nature of that structure shall be permitted.
B. 
No alteration, reconstruction, extension, or structural change to a single- or two-family residential structure that increases the nonconforming nature of that structure shall be permitted unless there is a finding by the Board of Appeals that the proposed alteration, reconstruction, extension, or structural change will not be substantially more detrimental to the neighborhood.
6.2.2 
Nonconforming Structures Other Than Single-Family or Two-Family Dwellings. Except as provided elsewhere in this By-law, the following provisions shall apply to nonconforming structures other than single-family or two-family dwellings:
A. 
A nonconforming structure may be altered, and the conforming use extended throughout the altered portion; provided, that the resulting alteration shall not cause the structure to further violate the dimensional regulations of the district in which it is located.
B. 
No building area or floor area, where already nonconforming, shall be increased so as to create a greater nonconformity.
C. 
A lawful nonconforming structure or portion thereof that has come into conformity shall not again become nonconforming.
D. 
A nonconforming structure shall not be moved to any other location on the lot or any other lot unless every portion of the structure, the use thereof, and the lot shall be conforming.
6.2.3 
Nonconforming Structures in Existence; Enforcement.
A. 
If real property has been improved and used in accordance with the terms of the original building permit, no criminal or civil action intended to compel the abandonment, limitation or modification of the use allowed by the permit or the removal, alteration, or relocation of a structure erected in reliance upon the permit by reason of an alleged violation of G.L. c. 40A or of this By-law shall be maintained unless the action, suit, or proceeding is commenced and notice of the action, suit, or proceeding is recorded in the registry of deeds or, in the case of registered land, the notice is filed in the registry district of the Land Court within six years of the commencement of the alleged violation.
B. 
No criminal or civil action intended to compel the removal, alteration, or relocation of a structure by reason of an alleged violation of this chapter or this By-law or the conditions of a variance or special permit shall be maintained unless the action, suit, or proceeding is commenced and notice of the action, suit, or proceeding is recorded in the registry of deeds or, in the case of registered land, the notice is filed in the registry district of the Land Court within 10 years of the commencement of the alleged violation.
C. 
If real property has been improved by the erection or alteration of one or more structures and the structures or alterations have been in existence for a period of at least 10 years and no notice of an action, suit, or proceeding as to an alleged violation of G.L. c. 40A or of this By-law has been recorded in the Registry of Deeds or, in the case of registered land, has been filed in the registry district of the Land Court within a period of 10 years from the date the structures were erected, then the structures shall be deemed, for zoning purposes, to be legally nonconforming structures subject to G. L. c. 40A, §6, and to this By-law.
6.2.4 
Unsafe Structures. Any nonconforming structure that has not been abandoned and is determined to be unsafe may be restored to a safe condition, provided such work on the structure shall be completed within two years of the determination that the structure is unsafe and it shall not place the structure in greater nonconformity. The Board of Appeals may by special permit waive this condition or extend the completion period.
Unless the Board of Appeals has made the findings prescribed in G.L. c. 40A, §6:
A. 
A nonconforming use, except for agriculture, horticulture, or floriculture, as defined in G.L. c. 128, §1A, of any open space on a lot outside a structure, or of a lot not occupied by a structure, shall not be extended.
B. 
A nonconforming principal use of a structure shall not be extended. However, any nonconforming use of structure may be changed to another nonconforming use by special permit provided the Board of Appeals finds that the new use is not a substantially different use and not more detrimental to the neighborhood than the existing use.
C. 
A nonconforming accessory use of a portion of a structure or any conforming accessory use of a portion of a nonconforming structure may be extended up to a maximum of 40 percent of the floor area of the existing structure.
D. 
A nonconforming use which has been changed to a permitted use shall not again be changed to another nonconforming use.
A. 
Any lot, or open space on a lot, including yards and setbacks, shall not be reduced or changed in area or shape such that the lot, open space, yard, or setback is made nonconforming or more nonconforming unless a special permit has been granted under the provisions of this By-law. However, this Section 6.4 shall not apply in the case of a lot a portion of which is taken for a public purpose.
B. 
A nonconforming lot which has come into conformity shall not again be changed to a nonconforming lot.
C. 
Any off-street parking or loading spaces, if already equal to or less than the number required to serve their intended use, shall not be further reduced in number except as provided in Section 7.1.
A. 
Reconstruction of a legally nonconforming structure damaged or destroyed by fire or other accidental or natural cause shall be allowed if the reconstruction is substantially in the form it had at the time of damage or destruction, or in any form if within applicable setback requirements and not larger than previously, and if reconstruction is started within 24 months and completed within 36 months of the damage or destruction.
B. 
A nonconforming use shall be considered abandoned when the premises have been devoted to another use, or when the characteristic equipment and the furnishing of the nonconforming use have been removed from the premises and have not been replaced by similar equipment within two years unless other facts show intention to resume the nonconforming use.
C. 
A nonconforming use or structure that has been abandoned, demolished without reconstruction, or not used for a period of two years or more shall lose its protected status and shall be subject to all provisions of this By-law; however, the Planning Board may grant a special permit to authorize the reestablishment of a nonconforming use or structure where such reestablishment shall not result in substantial detriment to the neighborhood. The Planning Board shall consider the lot size, the existing building coverage, and available on-site parking based upon review of the specific characteristics of the site, including, but not limited to, available area, traffic patterns, access to public ways, intended use of the site, and protection of public safety and convenience, except that any use so allowed shall not be more substantially detrimental to the neighborhood than the previous use.
D. 
Any nonconforming use that has either been abandoned or that has not been used for two years or more shall lose the protections accorded under this By-law and shall be required to conform to the current By-law.
E. 
A nonconforming structure determined by the Zoning Enforcement Officer to be unsafe may be restored to a safe condition, provided such work on any nonconforming structure shall be completed within one year of the determination that the structure is unsafe and it shall not place the structure in greater nonconformity. The Board of Appeals may by special permit extend the completion period.
Exempted from the requirement for a special permit under this Section 6.6 are the following:
A. 
Alteration, reconstruction, extension, or structural change (collectively "alteration") of a nonconforming single- or two-family residential structure shall not be considered an increase in the nonconforming nature of the structure and shall be permitted as of right under the following circumstances:
1. 
Normal repairs or replacement of parts of any nonconforming structure; provided, that such repair or replacement does not constitute an extension of a nonconforming use of such structure.
2. 
Alteration to a conforming structure where the alteration will also comply with all applicable sections of the Zoning By-laws in effect at the time of application, if the existing structure is located on a lot which is nonconforming as the result of a zoning change.
3. 
Alteration within the existing footprint of a nonconforming structure to comply with requirements of the Massachusetts Building Code.
4. 
Alteration to a nonconforming structure where the alteration will comply with all applicable sections of the Zoning By-laws in effect at the time of application and will not increase the habitable space.
5. 
Alteration to a nonconforming structure on a lot of at least 20,000 square feet, where the alteration will comply with all applicable sections of the Zoning By-laws in effect at the time of application, including, but not limited to, setback, yard, building coverage, and height requirements.
6. 
In cases where the applicant seeks to increase the height of any structure that encroaches on a required setback, where any increase in height will occur within such encroachment, there shall be no alteration as of right under this section.
B. 
Interior alteration of any otherwise conforming structure that does not change the nature of, nor increase the intensity of, a nonconforming use, and interior alterations of preexisting nonconforming structures for a use or uses which are otherwise allowed by zoning.
C. 
Reconstruction of a legally nonconforming structure damaged or destroyed by fire or other accidental or natural cause, other than flood damage sustained to structure within any floodplain shown on the flood insurance rate maps of Southbridge, if the reconstruction is substantially the form it had at the time of damage or destruction, or in any form if within applicable setback requirements and not larger than previously, and if reconstruction is started within 24 months and completed within 36 months of the damage or destruction.
D. 
Nonconforming uses and structures in the Watershed Protection District may be extended or altered through the issuance of a special permit by the Planning Board upon a finding that such extension or alteration shall not be substantially more detrimental to the water supply than the existing use. A nonconforming use shall not be changed to another nonconforming use.
E. 
Reconstruction of any permitted commercial accommodation structure or unit(s), if for the purpose of rehabilitation or upgrade, and if the commercial accommodation was licensed and operational for the three years prior to the rehabilitation or upgrade. The reconstruction shall not allow rebuilding at a greater density, greater height, or at a different location than previously existed.
F. 
Not exempted under this section are accessory uses and structures.