(1) Except as provided in paragraph (2), the length
of a superstructure (S) shall be the mean length of the parts of the
superstructure which lie within the length (L).
Where a superstructure bulkhead is recessed, the effective
length of the superstructure shall be reduced by an amount equal to
the area of the recess in plan view divided by the breadth of the
superstructure at the midlength of the recess. Where the recess is
unsymmetrical about the centreline, the largest portion of the recess
shall be considered as applying to both sides of the ship. A recess
need not be decked over.
(2) Where the end bulkhead of an enclosed superstructure
extends in a fair convex curve beyond its intersection with the superstructure
sides, the length of the superstructure may be increased on the basis
of an equivalent plane bulkhead. This increase shall be twothirds
of the fore and aft extent of the curvature. The maximum curvature
which may be taken into account in determining this increase is onehalf
the breadth of the superstructure at the point of intersection of
the curved end of the superstructure with its side.
Where there is an extension to a superstructure, which extension
has a breadth on each side of the centre line at least 30% of the
breadth of the ship, the effective length of the superstructure may
be increased by considering an equivalent superstructure bulkhead
in the form of a parabola. This parabola shall extend from the extension
at the centreline and pass through the junction of the actual superstructure
bulkhead with the sides of the extension and extend to the sides of
the ship. This parabola shall be completely contained within the boundary
of the superstructure and its extensions.
If the superstructure is setin from the side, up to the
limit allowed under regulation 3(10), the
equivalent bulkhead should be calculated on the basis of the actual
breadth of the superstructure (and not the breadth of the ship).
(3) Superstructures which have sloped end bulkheads
shall be dealt with in the following manner:

(a) When the height of superstructure, clear of
the slope, is equal to or smaller than the standard height, length
S is to be obtained as shown in figure 34.1.

(b) When the height is greater than the standard,
length S is to be obtained as shown in figure
34.2.

(c) The foregoing will apply only when the slope,
related to the base line, is 15° or greater. Where the slope is
less than 15°, the configuration shall be treated as sheer.
Figure 34.1 Height of superstructure equal to or smaller than the standard height
h
Figure 34.2 Height of superstructure greater than the standard height