46 CFR 42.25-10: Superstructure, double bottom tanks and bulwarks
Last reviewed: October 14, 2026
This section sets construction requirements for a vessel. It covers the forecastle and aft superstructure, watertight subdivision of double bottom tanks, and bulwarks or rails.
What it says
Vessels must have a forecastle of at least standard height and a length of at least 0.07L.
46 CFR 42.25-10(a)(1)“Vessels, shall have a forecastle of at least standard height and a length of at least 0.07L.”
If the vessel is less than 328 feet in length, it must also have a poop of at least standard height, or a raised quarter deck with either a deckhouse or a strong steel hood of at least the same total height, fitted aft.
46 CFR 42.25-10(a)(1)“if the vessel is less than 328 feet in length, a poop of at least standard height, or a raised quarter deck with either a deckhouse or a strong steel hood of at least the same total height shall be fitted aft.”
Double bottom tanks fitted within the midship half length of the vessel must have adequate watertight longitudinal subdivision.
46 CFR 42.25-10(b)(1)“Double bottom tanks where fitted within the midship half length of the vessel shall have adequate watertight longitudinal subdivision.”
The vessel must have either permanent bulwarks at least 39 1/2 inches in height, or efficient rails of the same height and of specially strong construction.
46 CFR 42.25-10(c)(1)“or with efficient rails of the same height and of specially strong construction”
Permanent bulwarks must be specially stiffened on the upper edge, supported by strong bulwark stays attached to the deck, and provided with necessary freeing ports.
46 CFR 42.25-10(c)(1)“specially stiffened on the upper edge and supported by strong bulwark stays attached to the deck and provided with necessary freeing ports”
Common questions
How long must a forecastle be under this section?
A forecastle must be at least standard height and have a length of at least 0.07L.
“Vessels, shall have a forecastle of at least standard height and a length of at least 0.07L.”
Does a vessel under 328 feet need a poop?
A vessel less than 328 feet in length must also have a poop of at least standard height, or a raised quarter deck with a deckhouse or strong steel hood of at least the same total height, fitted aft.
“if the vessel is less than 328 feet in length, a poop of at least standard height, or a raised quarter deck with either a deckhouse or a strong steel hood of at least the same total height shall be fitted aft.”
How high must bulwarks or rails be?
Permanent bulwarks must be at least 39 1/2 inches in height. Efficient rails of specially strong construction must be the same height.
“or with efficient rails of the same height and of specially strong construction”
The text of 46 CFR 42.25-10
Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR
Construction of vessel
(a) Superstructure. (1) Vessels, shall have a forecastle of at least standard height and a length of at least 0.07L. In addition, if the vessel is less than 328 feet in length, a poop of at least standard height, or a raised quarter deck with either a deckhouse or a strong steel hood of at least the same total height shall be fitted aft.
(b) Double bottom tanks. (1) Double bottom tanks where fitted within the midship half length of the vessel shall have adequate watertight longitudinal subdivision.
(c) Bulwarks. (1) The vessel shall be fitted either with permanent bulwarks at least 39 1/2 inches in height, specially stiffened on the upper edge and supported by strong bulwark stays attached to the deck and provided with necessary freeing ports, or with efficient rails of the same height and of specially strong construction.
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.