Lumber question for those in the building trades
It is because of shrinkage. The nominal dimensions are for green, rough lumber as cut at the saw mill. As it loses moisture, a piece of lumber will shrink on a percentage basis, say 6%. 6% of 8" or 10" is more than 6% of 4" or 6". The attached chart shows Doug Fir. Others woods shrink more. So the board shrinks when air drying/kiln drying and then gets planed to final size.
But everyone is also right that old 2x4's used to measure 1 5/8 x 3 5/8. Now they are 1 1/2 x 3 1/2.
It is because of shrinkage. The nominal dimensions are for green, rough lumber as cut at the saw mill. As it loses moisture, a piece of lumber will shrink on a percentage basis, say 6%. 6% of 8" or 10" is more than 6% of 4" or 6". The attached chart shows Doug Fir. Others woods shrink more. So the board shrinks when air drying/kiln drying and then gets planed to final size.
But everyone is also right that old 2x4's used to measure 1 5/8 x 3 5/8. Now they are 1 1/2 x 3 1/2.
