TM 55-07/NAVSEA OP 3221 Rev 2
Figure 7-28. Class 'A" magazine under construction (nonportable).
(1) The complete boarding over (encasement) of all metal surfaces or structures is a basic requisite of
magazine construction. The interior of magazines constructed of steel, therefore, must be entirely protected by wood at
least three-fourths of an inch thick. All ship's structures within magazines constructed entirely of wood, including
overhead beams or hatch coaming that is within 12 inches of the top of the stowed explosives, will also be boarded over.
Bare steel decks within the magazine will be covered with a wooden floor consisting of at least two crosswise layers of
commercial 1-inch lumber at least 4 inches wide. Existing decking needs to be covered with only one course of
dunnage. All flooring should be fitted as close as possible, edge-to-edge and butt-to-butt.
(2) Figure 7-26 shows the construction details for the framework of a nonportable wooden class "A" magazine
constructed along the side of a ship. The horizontal braces (kickers) extend to the hull plate, as shown, or to strip
sheathing secured over the sweatboards. Spacing of the braces should not exceed 36 inches; however, the length of the
braces will be determined by regulations governing the separation of the class of explosive from the ship's skin. For
Coast Guard classes VIII and IXC, this distance should not be less than 8 feet. Uprights will not be stepped directly onto
a metal deck; instead, a 2by 4-inch bearer is used to carry the uprights. The illustration shows that bearers are not
required when wood decking is present. A 2by 4-inch header will be fitted between the overhead and the tops of the
(3) During construction, care should be taken to ensure that nails do not penetrate into the magazine and that
the interior boards are fitted and finished to form a smooth surface. When a metal stanchion, post, or other obstruction is