No nonconforming use shall be extended, except by variance granted pursuant to N.J.S.A. 40:55D-70d. However, where a building meets the use requirements of this chapter but is nonconforming because of height, width, depth or yard requirements, said building may be altered or enlarged, provided that the height, area, coverage, FAR, yard or any other regulations in this chapter are not violated; for example, if a front yard is nonconforming, this does not preclude a conforming addition to the rear within the rear setback line.