No building or structure shall be hereinafter erected; nor shall any existing building or structure be altered, enlarged or moved; nor shall any lot, yard, lot width, open space or loading or parking space required in relation to any building or structure or use be encroached upon or reduced, in any manner not in conformity with the lot area, lot area per family, lot coverage, open space and building bulk regulations, yard requirements and other space and area regulations designated herein for the district in which it is located, unless such reduction is by a duly constituted public authority for a public purpose.