No building or other structure shall hereafter be erected, altered or enlarged, nor shall any use of land be established or enlarged on a lot or tract of land which is:
A. Smaller in area than the minimum lot area prescribed for the zoning district in which the building, structure or land is located; or
B. Less than the minimum lot width prescribed for the zoning district in which the building, structure or land is located. (1979 Code § 5-3-4)