Dimensional lumber is a term used for lumber that
is finished/planed and cut to standardized width and depth
specified in inches.
Common sizes are 2×4 (pictured, also two-by-four
and other variants, such as four-by-two in the UK,
Australia, New Zealand), 2×6, and 4×4. The length of a board
is usually specified separately from the width and depth. It
is thus possible to find 2×4s that are four, eight, or
twelve feet in length.
Standard lengths of lumber are 6, 8, 10, 12, 14,
16, 18, 20, 22, and 24 feet.
A grade stamp is printed on
lumber produced in North America, but what does it mean?
Since lumber comes from a natural source, much of it has
naturally occurring defects, such as large knots or splits,
and these can reduce its strength. Because of these and less
obvious defects, lumber that leaves a sawmill must be
appraised by trained inspectors and assigned a grading
"Select" = at least 80%
clear wood Lumber grade stamp
"#1 Structural" = at least
75% clear wood; SPF (Spruce, Pine, Fir): Due to
similar appearance and structural properties, these three
softwood specie are commonly processed and sold under the
grade stamp of "SPF." Because "SPF" lumber is readily
available, light weight and easy to nail.
"#2 Structural" = at least
66% clear wood; # 2 & Better Grade: Lumber is graded
according to the size and location of commonly found
defects, such as knots and wane. The grain orientation
within each board is also considered, to determine its
structural integrity and strength capacity. Ultimately, an
official grade is designated which is typically proportional
to the amount of clear wood. The grade of "#2 & Better" is
approximately 65% clear wood and is considered to be the
preferred grade for construction purposes.
"#3 Structural" ("stud" grade)
= at least 50% clear wood;
"Construction Grade" = at least 57%
"Standard Grade" = at least 43% clear wood;
"Utility Grade" = at least 29% clear wood.