bunk

A bunk is a fixed bed frame built into the hull or superstructure of a vessel, designed to provide sleeping berths for crew in the confined spaces typical of ships. Unlike a conventional bed, a bunk is integral to the ship's construction, secured against the hull or bulkhead, and sized to fit the dimensions of crew quarters rather than standard domestic rooms. On most working vessels, bunks are arranged in tiers, usually two or three high, with each bunk accessed by a short ladder or climbing rail.

The vertical stacking of bunks is driven by the premium placed on usable deck space aboard ship. A cabin that might hold one traditional bed instead accommodates two or three bunks, each typically 75 to 80 centimetres wide and roughly 190 centimetres long. The vertical gap between bunks is usually 75 to 90 centimetres, leaving enough clearance for a crew member to lie down or sit up without difficulty. The lowest bunk sits just above deck level; the highest may reach nearly to the deck head, or ceiling.

Bunks are fitted with mattresses, often foam-based and treated for salt resistance and mildew. A canvas lee cloth (or lee board) is stretched along the outboard edge of each bunk to prevent the occupant from rolling out during heavy weather or rough seas. On modern vessels, bunks are sometimes fitted with adjustable ventilation ducts or individual reading lights. The frame is usually welded steel tubing, occasionally aluminium on higher-specification vessels, and is bolted to the ship's structure.

The arrangement of bunks varies by vessel type and crew size. Cargo ships and tankers typically house crew in berths of two or four, while fishing vessels often use single-berth cabins for senior crew and shared bunk rooms for ordinary seamen. Cruise ships and naval vessels may have cabins with upper and lower bunks for officers or single berths for ratings. The quality and space standards for crew bunks are specified in conventions such as the ILO Maritime Labour Convention and class society rules.

Problems with bunks centre on ventilation, condensation, and deterioration. Poor air circulation in bunked cabins promotes mildew and mold growth, particularly in tropical or high-humidity climates. Rusting of steel frames occurs when saltwater spray penetrates external bulkheads or when fresh water leaks from deck above. The term itself derives from the Scandinavian and Dutch maritime tradition, predating the industrial era but essential to the practical operation of merchant and naval vessels for centuries.