a horizontal covering in the hull of a vessel, extending along the vessel’s entire length. Unlike a deck, a covering located over part of the length or width of a vessel is known as a platform. A ship’s hull may have one deck or several decks and platforms. The deck consists of plating, which consists, in turn, of deck plating proper and a deck stringer along the line where the deck joins the side of the ship, and the framing (beams, carlings, and so forth).
The upper deck provides the basic longitudinal bracing for the ship’s hull, giving the hull overall strength and lateral stiffness. The deck atop the watertight bulkheads is known as the main deck. The height of the main deck over the waterline is the measure of the vessel’s freeboard. The main deck may be the upper deck or, on ships with shelter decks or with continuous superstructures, it may be the second deck from the top. The upper deck accommodates cargo-handling gear on cargo vessels, staterooms on passenger ships, and armament on warships.
Lower decks are used on cargo vessels for dividing cargo space by height and for stowage of cargo. On passenger ships, the lower decks are used for staterooms, common rooms, and auxiliary spaces, and on commercial fish-processing vessels they contain processing equipment. The space between the upper and lower decks is called the tween deck, and the space below the lowest deck is called the hold. The openings in the upper deck (hatches) are framed with coamings and equipped with watertight covers. Decks over the superstructure are called supersructure decks. Partial decks over the main deck are distinguished by function; examples include boat decks and promenade decks. Deck thickness and deck framing dimensions for civilian vessels are regulated by the classification societies.
E. G. LOGVINOVICH