It’s because the actual cut is 2x4, and the wood shrinks. The typical shrinkage is known and accounted for. It is a treat when a house has an actual 2x though, i.e., it was cut divided by the shrinkage ratio, or cut dry. Related to why framing is done “on center”, i.e., “16 on center”.
What’s even more annoying is that a 2x4 (pronounced two-by-four) isn’t 2 by 4 inches. It’s 1.5 x 3.5 (sometimes even a 1/16 under).
It’s all because of some unfinished lumber bullshit, but it’s still not as confusing as pipe and hose fitting sizing at least.
Unless you’re in the south, in which case it’s pronounced “tuba-fur”.
And I also forgot about the Mainers and their two-by-faws
It’s because the actual cut is 2x4, and the wood shrinks. The typical shrinkage is known and accounted for. It is a treat when a house has an actual 2x though, i.e., it was cut divided by the shrinkage ratio, or cut dry. Related to why framing is done “on center”, i.e., “16 on center”.