What is the actual size of 2x4 lumber?
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Also question is, when did 2x4 become smaller?
Size standards, maximum moisture content, and nomenclature were agreed upon only as recently as 1964. The nominal 2x4 thus became the actual 1½ x 3½, imperceptibly, a fraction of an inch at a time. It was a 34 percent reduction in actual volume; as those in the trade would say, it's “selling air.”
Similarly, why is lumber not actual size? Maybe you've noticed that lumber sizes are often misleading. The "nominal" cross-section dimensions of a piece of lumber, such as 2 X 4 or 1 X 6, are always somewhat larger than the actual, or dressed, dimensions. The reason is that dressed lumber has been surfaced or planed smooth on four sides (called S4S).
Beside this, why is a 2x4 actually 1.5x3 5?
The 2x4 refers to the rough-cut green wood: it shrinks during drying, then the dried wood is planed smooth, so the finished lumber is supposed to end up at 1.5"x3. 5". While it doesn't really shrink that much, the mills get more usable finished 2x4's from a given tree if they cut them slightly smaller to begin with.
Is a 4x4 really 4 inches?
Believe it or not, there actually is some rhyme and reason for why the actual measurements of dimensional lumber don't match their names.
Actual Dimensions and Nominal Dimensions.
|Nominal Measurement||Actual (inches)||Actual (mm)|
|2 x 12||1-1/2 x 11-1/4||38 x 286|
|4 x 4||3-1/2 x 3-1/2||89 x 89|
|4 x 6||3-1/2 x 5-1/2||89 x 140|