2x refers to the nominal thickness of framing lumber
as in 2x4 is nominal 2" thick and nominal 4" wide
but a 2x4 is actually 1.5" thick and 3.5" wide
This standard continues to 2x6, 2x8 and above have smaller widths, a 2x8 is actually 1.5x7.25
o.c. stands for on center
meaning two 2x4s placed 16" oc in a typical wall would be: 16" measured from the center of one stud to the center of the next stud, 17.5" measured from the outside edge to outside edge, and 14.5" measured from inside edge to inside edge. |