In R-1 districts each one-family dwelling, together with its accessory buildings,
hereafter erected, shall require a lot area of not less than 15,000 square feet when
said lot is not served by either a municipal water or a municipal sewerage system;
shall require a lot area of not less than 12,000 square feet when said lot is served
either by a municipal water system or a municipal sewerage system; shall require a
lot area of not less than 9,600 square feet when both a municipal water and a municipal
sewerage system are available, and said lot shall have a width of not less than 80
feet at the front or rear building lines; provided, however, that this requirement
shall not apply to any lot which at the time the ordinance from which this article
is derived became effective was narrower at the street line or lesser in area than
the specifications herein provided, if such lot was of record at the time of the adoption
of the ordinance from which this article is derived.