Any lot in a single ownership, which ownership was of record on May 18, 1965, that does not meet the requirements of this chapter for yards, courts or other areas of open space, may be utilized for single residence purposes, provided the requirements for such yard or court area, width, depth or open space are within 75% of that required by this chapter. The purpose of this provision is to permit utilization of recorded lots which lack adequate width or depth as long as reasonable living standards can be provided.