Section 67(4) in Kolkata Municipal Corporation Building Rules, 2009
(4)Notwithstanding anything contained in sub-rule (3), if all sides of an interior open space are enclosed by a combination of higher and lower blocks of a building, then minimum dimension of such interior open space shall be governed by the height of lower block provided that in no case the covered "area of" such lower block shall be less than-25% of the total Covered area of the concerned building constituting the interior open space.
