Any building or use of a building or use of land or part thereof lawful at the time this chapter is adopted (1939) may be continued, unless and until abandoned, although such building or use does not conform to the provisions hereof. No extension of the nonconforming use of a building, including adding to, enlarging, reconstructing or replacing, shall be allowed unless such addition, enlargement, reconstruction or replacement is used for the purpose or for a purpose substantially similar to the purpose for which the original building may be lawfully used and unless authorized by the Board of Appeals and subject to appropriate conditions, limitations or safeguards stated in writing by said Board and made a part of the permit. As a basis for such permit, the Board must be satisfied only that such addition, enlargement, reconstruction or replacement, and the use to be made thereof, will not substantially increase any detrimental or injurious effect of the building or use on the neighborhood.

(Reserved)

A nonconforming structure or use damaged or destroyed by accidental causes may be repaired, reconstructed or restored either within the same portion of the lot or within a different portion of the lot, provided that doing so renders the structure less nonconforming than previously, and used as before, provided that such repair, reconstruction or restoration shall be completed within two (2) years of said accidental damage or destruction.

Any such structure that is being used as a single-family dwelling or a two-family dwelling may be increased in size or otherwise altered without a special permit or other ruling from the Board of Appeals, provided the Building Commissioner determines, prior to the issuance of a building permit for such addition or alteration, that the addition or alteration will not intensify any existing nonconformities.