(1) In every ship of which the hull is constructed of metal every deck which forms the crown of any part of the crew accommodation (in this section called an "overhead deck"), and which is exposed to the weather shall be made of metal and shall either-
(a) be covered on its upper side with-
(i) wood not less than 57 millimetres thick, properly laid and caulked; or
(ii) a material complying with the requirements specified in Schedule 1 and properly laid; or
(b) be insulated on its underside with a material complying with the requirements specified in Schedule 2.
(2) In every ship in which the hull is not constructed of metal, the overhead decks shall be constructed of wood not less than 63 millimetres thick properly laid and caulked or of other suitable material having properties of watertightness and insulation equivalent to such a wooden deck.