StructuralAid
StructuralAid
StructuralAid

Selecting Lumber

The quality of lumber available at local lumber yards has decreased over past decades. There are several reasons for this, including the depletion of old-growth timber, new forestry practice of harvesting younger trees, etc. Given this unfortunate state of affairs, a few pointers are provided below for selecting your lumber for that next project. But first, let’s define some terms.

A ‘crown’ or ‘crook’ is a bow along the strong axis, or a smile/frown in a 2×4 that is 3.5″ thick. A ‘bow’ is a bow along the weak axis, or smile/frown that is 1.5″ thick. To get a better idea of this, it is much easier to cause a board to ‘bow’ when stepping on its wide side, then it is to cause a ‘crown’ by stepping on its narrow side.

Now for the advice in choosing lumber:

  • Most 2x boards are at least slightly crowned. More severe crowning is generally less acceptable then bowing, because a bow often be more easily corrected during installation, where a crown is more difficult to correct due to resistance by the strong axis.
  • Sawn lumber boards that have wane on them are usually straighter. So if one side of the boards will be hidden, and they are not being used for a structural purpose, then consider looking for these.
  • Usually straight 2x boards are found together in the same stack. So if you start finding straight lumber, keep looking at that area. The reverse holds true, if you find a few badly twisted boards in a row, move to another pile or area.
  • Look at the board, there may be a change in direction at a central knot, but otherwise the board may consist of two relatively straight portions. If you need to cut a 2x4x8 into two 3′ lengths, then such a board may work fine.
  • Stay away from boards in disarray or no longer stacked neatly. These most always have been previously rejected by another customer. And stay away from twisted boards, or boards with both a crown and a bow.
  • Pressure treated (PT) lumber is usually much wetter and straighter than it will be after drying out at your worksite for a few days. It is impossible to predict how much PT lumber will bow or even twist just by looking at it in the lumber yard. Give this, look for straight boards that are dryer because they are on the outside of the pile. Keep wet PT lumber out of direct sunlight after purchase.