---
kind: "section"
citation: "46 C.F.R. § 171.065"
title: "46"
number: "171.065"
heading: "Subdivision requirements— Type I."
url: "https://uscodex.org/cfr/46/171.065"
---

# §171.065. Subdivision requirements— Type I.

- (a) Except as provided in paragraphs [(c)](#c) and [(f)](#f) of this section, the separation between main transverse watertight bulkheads on a vessel, other than one described in [paragraph (b)](#b) of this section, must not exceed—
- (b) The factor of subdivision used to determine compliance with [paragraph (a)](#a) of this section must be the smaller of 0.5 or the value determined from Table 171.065(a) if—
  - (1) The vessel is 430 feet (131 meters) or more in LBP; and
  - (2) The greater of the values of Y as determined by the following equations equals or exceeds the value of X in Table 171.065(b):
- (c) The distance A in Figure 171.065 between main transverse watertight bulkheads may exceed the maximum allowed by paragraphs [(a)](#a) or [(b)](#b) of this section if each of the distances B and C between adjacent main transverse watertight bulkheads in Figure 171.065 does not exceed the smaller of the following:
  - (1) **The floodable length.**
  - (2) **Twice the separation allowed by paragraphs (a) or (b) of this section.**
- (d) In each vessel 330 feet (100 meters) or more in LBP, one of the main transverse watertight bulkheads aft of the collision bulkhead must be located at a distance from the forward perpendicular that is not greater than the maximum separation allowed by paragraph [(a)](#a) or [(b)](#b) of this section.
- (e) The minimum separation between two adjacent main transverse watertight bulkheads must be at least 10 feet (3.05 meters) plus 3 percent of the LBP of the vessel, or 35 feet (10.7 meters), whichever is less.
- (f) The maximum separation of bulkheads allowed by paragraphs [(a)](#a) or [(b)](#b) of this section may be increased by the amount allowed in [paragraph (g)](#g) of this section if—
  - (1) The space between two adjacent main transverse watertight bulkheads contains internal watertight volume; and
  - (2) After the assumed side damage specified in [paragraph (h)](#h) of this section is applied, the internal watertight volume will not be flooded.
- (g) **For the purpose of paragraph (f) of this section, the allowable increase in separation is as follows—**
- (h) **The assumed extents of side damage are as follows—**
  - (1) **The longitudinal extent of damage—** must be assumed to extend over a length equal to the minimum spacing of bulkheads specified in [paragraph (e)](#e) of this section.
  - (2) **The transverse extent of damage—** must be assumed to penetrate a distance from the shell plating equal to one-fifth the maximum beam of the vessel and at right angles to the centerline at the level of the deepest subdivision load line.
  - (3) **The vertical extent of damage—** must be assumed to extend vertically from the baseline to the margin line.
- (i) The maximum separation between the following bulkheads must not exceed the maximum separation between main transverse watertight bulkheads:
  - (1) The collision bulkhead and the first main transverse watertight bulkhead aft of the collision bulkhead; and
  - (2) **The last main transverse watertight bulkhead and the aftermost point on the bulkhead deck.**
- (j) The minimum separation between the following bulkheads must not be less than the minimum separation between main transverse watertight bulkheads:
  - (1) The collision bulkhead and the first main transverse watertight bulkhead aft of the collision bulkhead; and
  - (2) **The last main transverse watertight bulkhead and the aftermost point on the bulkhead deck.**

## Notes

### Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by USCG-2007-0030, 75 FR 78085, Dec. 14, 2010]

### Authority

Authority: 46 U.S.C. 2103, 3306; E.O. 12234, 45 FR 58801, 3 CFR, 1980 Comp., p. 277; Department of Homeland Security Delegation No. 0170.1.

### Source

Source: CGD 79-023, 48 FR 51017, Nov. 4, 1983, unless otherwise noted.

### Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by USCG-2007-0030, 75 FR 78085, Dec. 14, 2010]