Hull Construction Regulations — 6
6 (1) Compartments exceeding the permissible length: (a) a compartment may exceed its permissible length provided that the combined length of each pair of adjacent compartments to which the compartment in question is common does not exceed either the floodable length or twice the permissible length, whichever is the lesser; (b) if one compartment of either of such pairs of adjacent compartments is situated inside the machinery space, and the other compartment thereof is situated outside the machinery space, the combined length of the two compartments shall be adjusted in accordance with the mean average permeability of the two portions of the ship in which the compartments are situated; (c) where the lengths of two adjacent compartments are governed by different factors of subdivision, the combined length of the two compartments shall be determined proportionately; and (d) where in any portion of a ship bulkheads required by these Regulations to be watertight are carried to a higher deck than in the remainder of the ship, separate margin lines may be used for calculating the floodable length of that portion of the ship, if (i) the two compartments adjacent to the resulting step in the bulkhead deck are each within the permissible length corresponding to their respective margin lines and, in addition, their combined length does not exceed twice the permissible length determined by reference to the lower margin line of such compartments, and (ii) the sides of the ship are extended throughout the ship’s length to the deck corresponding to the uppermost margin line and all openings in the shell plating below that deck throughout the length of the ship comply with the requirements of section 19 as if they were openings below the margin line. Additional Subdivision at Forward End (2) In ships 131 m in length and upwards, the watertight bulkhead next abaft the collision bulkhead shall be fitted at a distance from the forward perpendicular that is not greater than the permissible length appropriate to a compartment bounded by the forward perpendicular and such bulkhead. Steps in Bulkheads (3) If a bulkhead required by these Regulations to be watertight is stepped, it shall comply with one of the following conditions: (a) in ships having a factor of subdivision not greater than 0.9, the combined length of the two compartments separated by such bulkhead shall not exceed 90 per cent of the floodable length or twice the permissible length, whichever is the lesser; in ships having a factor of subdivision greater than 0.9, the combined length of the two compartments shall not exceed the permissible length; (b) additional subdivision is provided in way of the step to maintain the same measure of safety as that secured by a plane bulkhead; or (c) the compartment over which the step extends does not exceed the permissible length corresponding to a margin line taken 76 mm below the step. Recesses in Bulkheads (4) If any part of a recess lies outside vertical surfaces on both sides of the ship situated at a distance from the shell plating equal to one fifth of the breadth of the ship and measured at right angles to the centre line at the level of the deepest subdivision load water line, the whole of such recess shall be deemed to be a step in a bulkhead for the purposes of subsection (3). Equivalent Plane Bulkheads (5) Where a bulkhead required by these Regulations to be watertight is recessed or stepped, an equivalent plane bulkhead shall be assumed in determining the subdivision. Minimum Spacing of Bulkheads (6) If the distance between two adjacent bulkheads required by these Regulations to be watertight, or their equivalent plane bulkheads, or the distance between transverse planes passing through the nearest stepped portions of the bulkheads, is less than 0.03L + 3.05 m, or 10.67 m, or 0.1L, whichever is the least, only one of those bulkheads shall be regarded as forming part of the subdivision of the ship; for Class V and Class VIII vessels