The applicable rear yard and rear yard equivalent regulations shall be modified as follows:

(a)        Permitted obstructions

In any rear yard or rear yard equivalent, any building or portion of a building used for commercial, manufacturing, or residential uses, other than dwelling units, shall be a permitted obstruction, provided that the height of such building shall not exceed one story, excluding basement, nor in any event 23 feet above curb level.

In addition, in M1-5 Districts paired with an R9X District north of Howard Street, in any rear yard, any building or portion of a building used for any permitted non-residential use, shall be a permitted obstruction, provided that the height of such building, or portion thereof, shall not exceed two stories, excluding basements, nor in any event 30 feet above curb level.

Any allowance for other permitted obstructions above a building in a rear yard or rear yard equivalent set forth in Section 43-23, shall be permitted above such modified height limitations.

(b)        Required rear yards

For all uses, a rear yard with a depth of not less than 20 feet shall be provided at every rear lot line on any zoning lot, except as follows:

(1)        no rear yard shall be required within 100 feet of the point of intersection of two street lines intersecting at an angle of 135 degrees or less;

(2)        whenever a front lot line of a zoning lot coincides with all or part of a street line measuring less than 230 feet in length between two intersecting streets, no rear yard shall be required within 100 feet of such front lot line; and

(3)        for interior lots where the depth of such zoning lot, or a portion thereof, is less than 90 feet, and such shallow depth was in existence on December 15, 1961 and on the date of application for a building permit, the required rear yard for such interior lot, or portion thereof, may be reduced by six inches for each foot by which the depth of a zoning lot, or portion thereof, is less than 90 feet. However, in no event shall the minimum depth of a required yard, or portion thereof, be reduced to less than 10 feet.

(c)        Required rear yard equivalents

For buildings, or portions thereof, containing non-residential uses, no rear yard equivalent shall be required on any through lot or through lot portion of a zoning lot.

For buildings, or portions thereof, containing residential uses, on any through lot that is 110 feet or more in maximum depth from street to street, a rear yard equivalent consisting of an open area with a minimum depth of 40 feet midway, or within 10 feet of being midway, between the two street lines upon which such through lot fronts, shall be provided.

However, for through lots where the depth of such zoning lot, or a portion thereof, is less than 180 feet, and such shallow depth was in existence on December 15, 1961 and on the date of application for a building permit, the required rear yard equivalent for such through lot, or portion thereof, may be reduced by one foot for each foot by which the depth of a zoning lot, or portion thereof, is less than 180 feet. However, in no event shall the minimum depth of a required yard, or portion thereof, be reduced to less than 20 feet.

(d)        Along district boundaries

The provisions of 43-30 (Special Provisions Applying Along District Boundaries), shall not apply along the district boundaries of two M1 Districts paired with Residence Districts.