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Common Woods—Continued | Up
Engineering Aid 3 - Beginning Structural engineering guide book | Next
Nominal and Dressed Sizes of Lumber |
Table 6-1.-Common Woods—Continued
Nominal, rough, green lumber has three
Grading
general classifications, according to size, as
follows:
1. BOARDS—less than 2 in. thick and 1 or
more in. wide. If less than 6 in. wide, they may
be classified as strips.
2. DIMENSION—at least 2 in. thick, but less
than 5 in. thick, and 2 or more in. wide. It may
be classified as framing, joists, planks, rafters,
studs, and small timbers.
3. TIMBERS—smallest dimension is 5 or
more in. They may be classified as beams,
stringers, posts, caps, sills, girders, and purlins.
Lumber classified by extent of manufacture
consists of three types as follows:
1. ROUGH LUMBER is not dressed (sur-
faced) but sawed, edged, and trimmed to the ex-
tent that saw marks show in the wood on the four
longitudinal surfaces of each piece for its overall
length.
2. DRESSED LUMBER is surfaced by a
planing machine to attain a smooth surface and
uniform size.
3. WORKED LUMBER is dressed and also
matched, shiplapped, or patterned.
According to the American Lumber Standards
set by the National Bureau of Standards for the
U.S. Department of Commerce, lumber is graded
for quality. The major grades of yard lumber, in
descending order of quality, are SELECT
LUMBER and COMMON LUMBER. Each of
these grades is subdivided, also in descending
order of quality.
SELECT LUMBER has a good appearance
and good qualities for finishing. One kind of select
lumber is suitable for natural finishes; another
kind, for painted finishes. Select lumber for
natural finishes is graded A or B. Grade A is
nearly free of defects and blemishes, but
Grade B contains a few minor blemishes. Select
lumber for painted finishes is Grade C or D. The
blemishes in Grade C are more numerous and
significant than those in Grade B. Grade D has
even more blemishes than Grade C does. Either
grade, C or D, presents a satisfactory appearance
when painted.
COMMON LUMBER is suitable for general
construction and utility purposes. It, also, is
subdivided by grade in descending order of
quality. No. 1 common is sound, tight-knotted
stock, containing only a few minor defects. It
must be suitable for use as watertight lumber.
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