To get that answer, we have to discuss a little more about the wood itself. So we know that standard sizes became important during WWI and WWII, but that still doesn’t seem to explain the discrepancy between nominal and actual sizes of dimensional wood. Commercial Lumber Sizes Chart Table - Engineers Edge WebRough lumber cannot be less than than 1/8 (3.2mm) thicker or wider than the nominal finished. ![]() Incidentally, grading lumber by specific standards began at about this same time as well. Those standard sizes required by the war effort resulted in the adoption of the same size standards that are still in use today. Those standards were revised several times until the demand for lumber during World War II led to the use of large quantities of wood in specific sizes. Actual size is anywhere from 1/4 inch to 3/4 inch less than nominal size. Actual dimensions may vary slightly between grades. If you have full-dimension lumber it is about 1.33 times stronger by being 2 inches instead of 1.5 inches (goes directly with thickness), and about 1.34 times for being 8 inches vs. Maximum lengths apply to molded grade only, extruded is continuous and limited only by transportation methods. The increasing demand for dimensional wood after World War I led to the first national size standards in 1924. 'A planed 2x8 is actually only 1.5 x 7.25 inches. ![]() At that time, sizes weren’t a problem because the needs of local carpenters were understood, and hand-fitting lumber, as they were building, was pretty normal. ![]() The board which is advertised and being sold by using nominal dimensions is a bit larger in size as compared to the actual size. Prior to that, until the middle of the 19 th Century, lumber was produced locally in the place where it would be used. 2×8 actual size A 2×8 board is 1 1/2 x 7 1/4 inches (38 x 184 mm) dimensions in actuality. Common Dimensional Lumber Sizes Softwoods such as Douglas fir, spruce, or Hem-Fir (a mixture of Western Hemlock and Amabilis Fir) used for building framing have the following nominal and actual dimensions. The need for a common size understanding between mills and the markets began over 100 years ago when lumber started traveling further to get to its destination via rail or boat. Actual size is anywhere from 1/4 inch to 3/4 inch less than nominal size. Actual Dimensions: 1.6875-in x 7.625-in x 12.
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