<P> The construction of Olympic and Titanic took place virtually in parallel , with Olympic 's keel laid down first on 16 December 1908 and Titanic 's on 31 March 1909 . Both ships took about 26 months to build and followed much the same construction process . They were designed essentially as an enormous floating box girder , with the keel acting as a backbone and the frames of the hull forming the ribs . At the base of the ships , a double bottom 5 feet 3 inches ( 1.60 m ) deep supported 300 frames , each between 24 inches ( 61 cm ) and 36 inches ( 91 cm ) apart and measuring up to about 66 feet ( 20 m ) long . They terminated at the bridge deck ( B Deck ) and were covered with steel plates which formed the outer skin of the ships . </P>
when was the titanic started to be built
31 March 1909