Section 50(3)(v) in West Bengal Municipal (Building) Rules, 2007
(v)For the purpose of this rule, if any interior open space or courtyard enclosed on three sides by a building or part thereof is meant to serve lighting and ventilation purpose to a part or whole of one side of one or more habitable rooms, the minimum width of such open space shall be 2.4 metres for buildings upto 14.5 metres in height, 3.5 metres for buildings above 14.5 metres upto 24.0 metres height, 5.0 metres for buildings above 24.0 metres upto 36.0 metres height, and 7.0 metres for all buildings above 36.0 metres height: