A decked structure on the freeboard deck extending from side to side or with the side plating not inboard of the shell plating more than 4% of the breadth (B), (ICLL). A superstructure may be a poop, a raised quarterdeck, a bridge, a forecastle or a full superstructure.
- Enclosed superstructure – The superstructure with bulkheads forward and/or aft fitted with weathertight doors and closing appliances.
- Full superstructure – A superstructure which, as a minimum, extends from the forward to the after perpendicular.