Section 5(2) in The Merchant Shipping (Tonnage Measurement Of Ships) Rules, 1960
(2)Such portion of the space above the crown of the engine-room and above the upper deck as is framed in for the machinery or for the admission of light and air shall not be included in the measurement of the spaces occupied by the propelling power machinery, unless the owner of the ship has applied in writing to the Central Government in that behalf:Provided that-------(a)the portion is first included in the measurement of the gross tonnage;(b)a surveyor certifies that the portion so framed in is reasonable in extent and is so constructed as to be safe and seaworthy, and that it cannot be used for any purpose other than the machinery or for the admission of light and air to the machinery or boilers of the ship.
