Section 67(3) in Kolkata Municipal Corporation Building Rules, 2009
(3)The minimum dimension of any side of every interior open space (a) at ground level, all sides of which are enclosed by a building or part thereof, shall be 30% of the height of the building, or 3.0 m., whichever is more (b) at any other level, all sides of which are enclosed by a building or part thereof, the height shall be measured from the said level where interior open space is formed.
