R1 R2 R3 R4 R5

1. Detached buildings#
   
   In the districts indicated, for zoning lots containing only single- or two-family detached residences, two side yards, shall be provided. In R1 Districts the minimum width of each side yard shall be eight feet, and in all other districts, the minimum width shall be five feet.

R3 R4 R5

1. Semi-detached buildings and zero lot line buildings
   
   In the districts indicated, for zoning lots containing only single- or two-family semi-detached or zero lot line residences, a side yard with a minimum width of five feet shall be provided. 
   
   In addition, where an adjoining zoning lot contains a single- or two-family detached semi-detached, or zero lot line residence, an open area with a minimum total width of eight feet shall be required between the building on the subject zoning lot and the residence on the adjacent zoning lot. However, where both adjoining zoning lots contain a single- or two-family detached semi-detached, or zero lot line residence, the total open area need not exceed 13 feet on the subject zoning lot.

R3-2 R4 R4B R5 R5B R5D

1. Other residences
   
   In the districts indicated, for zoning lots containing residences that are not subject to paragraphs (a) or (b) of this Section, no side yards shall be required. However, if any open area extending along a side lot line is provided at any level, it shall have a minimum width of five feet, measured perpendicular to the side lot line. Furthermore, where a zoning lot adjoins a zoning lot containing exclusively single- or two-family residences, and where a side yard with a minimum width of three feet or more is provided along the common side lot line, an open area with a minimum total width of eight feet shall be required between the building on the subject zoning lot and the residence on the adjacent zoning lot.
   
   The allowances for permitted obstructions in any yard or rear yard equivalent set forth in Sections 23-311 and 23-312 shall be permitted in such open areas.

R1 R2 R3 R4 R5

1. Permitted obstructions in open areas between buildings
   
   Only accessory mechanical equipment limited in depth to 18 inches from an exterior wall, chimneys, downspouts, eaves, gutters, open accessory off-street parking spaces, qualifying exterior wall thickness, ramps for access by people with disabilities, and steps as set forth in the applicable provisions of Sections 23-311 and 23-312 shall be permitted obstructions in open areas between buildings, provided that such obstructions, not including accessory off-street parking spaces, qualifying exterior wall thickness or accessory mechanical equipment, may not reduce the minimum width of the open area by more than three feet.