TM 55-607/NAVSEA OP 3221 Rev 2
d. Grades of Planks, Scantlings, and Heavy Joists.
(1) Planks, scantlings, and heavy joists of common-dimension lumber are graded in three numerical grades
under the American Lumber Standard Grades (a fourth grade is provided under some association grading rules).
Dimension lumber is graded mainly for strength, stiffness, and straightness. It is used mainly where stiffness is the
controlling factor, as in joists or studs, where the size of the member is determined by common building practice rather
than specifically designed to carry definite static (dead) or dynamic (live) loads. Grade 1 dimension lumber is a sound
grade in which knots are allowed, depending on the size of the knots with relation to the size of the piece. Features such
as pitch, torn grain, checks, and stains that do not materially affect the strength of the piece are not limited. Wane (bark,
or lack of wood for any cause, on an edge or corner of a board or timber) is limited to provide good nailing on one side
and two edges. This grade is used for joists and rafters in light framing and for less exacting items in heavier framing. It
is also used as planking for platforms and other heavy-duty flooring where the wearing surface rather than load-carrying
capacity is the important factor. Grade 2 dimension lumber permits coarse, sound knots to a limited extent, along with
warped pieces and certain types of decay. It has fair nailing edges and other features that will not weaken the piece to
an extent that will render it unfit for use.
(2) Grade 3 in American Standards and grade 4 in some association grading rules normally admit to
characteristic defects or size limitations that affect their utility for dunnaging. Therefore, grade 2 dimension is
recommended for dunnaging (construction grades under WCLIB, WWPA standards) structures. Again, in situations
where lower graded lumber meets the physical quality requirements set forth in this section, it may be used in place of
grade 2. Conversely, in situations where local grade 2 lumber does not meet these quality standards, higher graded
lumber must be procured.
e. Reclaimed Lumber. Lumber reclaimed as the result of a ship being discharged, and which satisfies the
requirements described in this section, is acceptable for dunnage as long as all split ends and nails are removed.
f. Regulation Lumber Sizes. The regulations in 46CFR146 provide for minimum sizes of lumber used for dunnage.
The regulations cite "commercial" sizes, which are the undressed nominal sizes. For additional information on lumber
sizes, refer to appendix B. Table 5-1 summarizes the regulation lumber sizes and construction techniques as specified
by 46CFR146 with alternate techniques that can be considered with special justification under the exemption procedures
specified by 46CFR146.02-25 and 49CFR107.
g. Green Lumber. Thoroughly seasoned lumber (that is, either air or kiln dried) is preferred for dunnaging since it
reduces the amount of dimensional change that the lumber may undergo as its moisture content varies in the ship's
environment. Since the effect of the ship's environment on green lumber during the timespan of a voyage is not well
documented, it is recommended that the usage of green lumber be restricted to situations in which seasoned lumber is
unavailable.
5-3. Plywood
a. General. Although plywood has limited application in securing operations, it is permitted as sheathing for
covering the interior of Class "A" magazines, and for decking and bulkheading in lieu of solid 2-inch boarding. In these
applications, the regulations specify 3/4-inch plywood and also require that, when used for the interior of a magazine, one
side be finished so as to form a smooth surface.
b. Applicable Specifications. Federal Specification NN-P-530, Flat Panel Plywood, covers the requirements for
softwood plywood that conforms to the commercial standard for Douglas-fir plywood (CS45), for western softwood
plywood (SC122), for pine plywood (ponderosa pine, sugar pine, and Idaho white pine), and for southern pine plywood
(CS259). These publications provide the detailed requirements for plywood that is suitable for dunnaging within the
Federal regulation requirements previously discussed. It is recommended that the softwood plywood used for dunnaging
be an exterior type of grade BC or CC, five or seven-ply, procured in 4 by 8-foot sheets.
c. Exterior Plywood. Exterior plywood has a high degree of moisture resistance and retains its original form and
strength when repeatedly wet and dried. The grades of exterior plywood that are commercially available (grades refer to
the quality of veneer used for the faces and inner piles) are provided in appendix B along with additional commercial
limitations that apply to the specific grades.
5-4. Nails
The nails used for fastening wood are common steel-wire nails, designated as type II, style 10, flathead, diamond-point,
bright, zinc or cement coated, smooth, as designated in Federal Specification FF-N-105, Nails, Wire, Brads, and Staples.
Generally, 8 penny (8d) nails are used for direct nailing of 1-inch lumber and 10 penny (10d) or 12
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