Sizes and specification
The approach to the primary conversion of hardwood logs varies to some extent, both by sawmill and by species. The industry works on principles designed to achieve maximum lumber yields, by cutting boards from around the log to optimise volume. As export demand grows, production techniques are being used to further improve yields of higher grades and to offer special cuts, such as rift and quarter sawn.
American hardwoods are produced in non-metric measure - lengths in feet, widths in inches, and thickness expressed in quarters of an inch. Therefore 1 inch (1") is expressed as 'four quarter', written as 4/4".
The standard thicknesses produced are:
3/4" (3/4" = 19.0mm)
4/4" (1" = 25.4mm)
5/4" (11/4" = 31.8mm)
6/4" (11/2" = 38.1mm)
8/4" (2" = 50.8mm)
10/4" (21/2" = 63.5mm)
12/4" (3" = 76.2mm)
16/4" (4" = 101.6mm)
Lumber is produced in random widths (measured to the nearest inch) usually 3" (76.2mm) and wider. Width specification will vary from producer to producer, by geographic region and by species, although ultimately it is the size of the tree that will be the determining factor. Generally, widths over 12" (304.8mm) are rare. Some producers do cut fixed widths as special requirements, but this tends to be part of further processing (described on pages 14-15 in the dimension and components section).
Lumber is produced in random lengths (measured to the next lowest foot) usually 4' (1.22m) and longer up to a maximum of 16' (4.88m), depending on the grade. As a general rule lengths over 12' (3.66m) are relatively rare. Some producers offer fixed lengths although availability tends to be limited.
Board feet are the units of measure used by the American hardwood lumber industry and are referred to as board measure. A board foot (bf) is 1' (0.30m) long, 1' wide and 4/4" (25.4mm) thick. Lumber prices are usually expressed in terms of cost per thousand board feet (mbf). 1,000 bf is equal to 2.36m3 (for 4/4" and thicker). Lumber cut to 3/4" (19mm), or planed below 4/4" is usually charged as 4/4" for weight purposes.