Lumber Terminology – A Few Basics

Have you ever gone to buy lumber and realized you couldn’t speak the language?  Here are a few basic terms to get you started:

Is it a hardwood or a softwood?  You may think this would refer to the hardness of the wood, but it is not so.  After all Balsa is in the hardwood group.  So what is the difference?  A good rule of thumb to determining the difference is in the leaves.  If the tree is deciduous  (has broad leaves and loses them in the winter) it is a hardwood.  Some examples are Oak, Maple, Ash, and Birch.  If on the other hand the tree is coniferous (it has needles and maintains them through the winter) it is a softwood;  for example Pine and Fir.

Is it Green or Dry?  This does not refer to color.  If it is freshly cut and not seasoned (dried)or treated it is Green.  It is wood as close to the natural state as possible and generally has a high moisture content. Much of the lumber you will find at the lumberyard will be either Air Dried or Kiln dried.   Both of the processes remove much of the natural moisture of the wood.

What is Pressure Treated Lumber? Pressure treated wood is wood that has undergone a process to make it more durable so that it is not susceptible to water, rot, termites, or fungus. It is typically used in outdoor applications such as decks where protection from weather and insects is important.

What is a board foot?  Most lumber is sold by the board foot which takes into account thickness and width of the board and not just the length.   To get a board foot multiply the length (in feet) x the width (in inches) x the height or thickness (in inches) and divide by 12 to get 1 board foot.

Most hardwoods are sold by the quarter inch in thickness.  A 4/4 piece of lumber will be approximately 1″ and a 5/4 will be 1.25″ and 8/4 with be 2″.   Surfaced lumber’s thickness will vary slightly in thickness and be slightly smaller, for example a 4/4 board may actually be anywhere from 3/4″ to 13/16″ thick.