On application, the City Planning Commission may, by certification, modify the underlying rear yard regulations and thereby allow single- or two-family residences to be built on the side or rear lot line, provided the following conditions are satisfied:

(a)        When a building is located on the side lot line, the entire required side yard equivalent shall be provided along the other side lot line of the same zoning lot. On the adjacent zoning lot there shall be a side yard of at least 10 feet, abutting the building wall which is located on the side lot line.

(b)        When a single- or two-family residence is located on the rear lot line, the zoning lots abutting the entire rear lot line shall provide a rear yard of at least 40 feet. If the building on either zoning lot has a height greater than two stories, then such building shall have a 10-foot rear setback above the height of the second story.

(c)        When single- or two-family residences share a party wall along the rear lot line, if at any level either building is set back from the rear lot line, each building shall have a setback at the same height and such rear setback shall be at least 20 feet in depth.

The Commission shall also find that:

(1)        such modifications of side or rear yards or equivalents blend harmoniously with the entire development;

(2)        there is no adverse effect with regard to adequate light and air to the residences;

(3)        such modification results in the maximum preservation of trees;

(4)        there is an agreement which provides access for maintenance of the building wall located on the lot line; and

(5)        a condition to the grant of any certification shall be that the requirements of Section 107-92 (Recordation) have been satisfied.