7 Special requirements concerning ship subdivision (R 7)

Where in a portion or portions of a ship the watertight bulkheads are carried to a higher deck than in the remainder of the ship and it is desired to take advantage of this higher extension of the bulkheads in calculating the floodable length, separate margin lines may be used for each such portion of the ship provided that: the sides of the ship are extended throughout the ship's length to the deck corresponding to the upper margin line and all openings in the shell plating below this deck throughout the length of the ship are treated as being below a margin line, for the purpose of Regulation 15; and the two compartments adjacent to the ‘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 based on the lower margin line. A compartment may exceed the permissible length determined by the rules of Regulation 4 provided 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 less. A main transverse bulkhead may be recessed provided that all parts of the recess lie inboard of 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 centreline at the level of the deepest subdivision load line. Any part of a recess which lies outside these limits shall be dealt with as a step in accordance with paragraph .6. Where a main transverse bulkhead is recessed or stepped, an equivalent plane bulkhead shall be used in determining the subdivision. Where a main transverse watertight compartment contains local subdivision and the Administration of the flag State is satisfied that, after any assumed side damage extending over a length of 3,0 metres plus 3 % of the length of the ship or 11,0 metres, or 10 % of the length of the ship whichever is the less, the whole volume of the main compartment will not be flooded, a proportionate allowance may be made in the permissible length otherwise required for such compartment. In such a case the volume of the effective buoyancy assumed on the undamaged side shall not be greater than that assumed on the damaged side. Allowance under this paragraph will only be made if such allowance is not likely to prevent compliance with Regulation 8. A main transverse bulkhead may be stepped provided that it meets one of the following conditions: the combined length of the two compartments, separated by the bulkhead in question, does not exceed either 90 % of the floodable length or twice the permissible length, except that, in ships having a subdivision factor equal to 1, the combined length of the two compartments in question shall not exceed the permissible length; additional subdivision is provided in way of the step to maintain the same level of safety as that secured by a plane bulkhead; the compartment over which the step extends does not exceed the permissible length corresponding to a margin line taken 76 mm below the step. In ships of 100 metres in length and upwards, one of the main transverse bulkheads abaft the forepeak shall be fitted at a distance from the forward perpendicular which is not greater than the permissible length. If the distance between two adjacent main transverse bulkheads, or their equivalent plank bulkheads, or the distance between the transverse planes passing through the nearest stepped portions of the bulkheads, is less than 3,0 metres plus 3 % of the length of the ship, or 11,0 metres, or 10 % of the length of the ship, whichever is less, only one of these bulkheads shall be regarded as forming part of the subdivision of the ship. Where the required subdivision factor is 0,50, the combined length of any two adjacent compartments shall not exceed the floodable length.

← FOR EXISTING CLASS B NON RO-RO PASSENGER SHIPS: 1,0 · All articles · NEW CLASS B, C AND D AND EXISTING CLASS B SHIPS: →

Source: EUR-Lex (Cellar) · retrieved 2026-11-10 · Text as adopted (Official Journal); later amendments are not incorporated in this text.