Worse still, the pattern does not continue like one would expect.
Nominal: 2x4 – Actual: 1.5" x 3.5"
Nominal: 2x6 – Actual: 1.5" x 5.5"
Nominal: 2x8 – Actual: 1.5" x 7.25"
Nominal: 2x10 – Actual: 1.5" x 9.25"
Nominal: 2x12 – Actual: 1.5" x 11.25"
There’s just an arbitrary point where they decided to take an extra 1/4" bite out of it. I’m not sure whether that’s more of an effect of shrinkage from kiln drying being proportional to the original length or an effect of industry practice to mill smaller boards to eke out more cuts per tree.
And for the record, yes, I am aware the discrepancy is not entirely explained by shrinkage. They do a planing step after drying. But the shrinkage is a not insignificant part of it. They have to round down to the nearest convenient dimension from wherever the shrinkage stops.
If longer boards shrink more, the finished boards would necessarily have to be smaller. I question whether that’s the effect at play, though, because I believe there was a phase in the industry where that extra quarter inch wasn’t taken off, and they changed their minds about it later.
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”.
That’s not from shrinkage (well the 1/16 might be, especially newer fast heated junk at the Homely Despot). It’s from when they mill the rough sawn 2x4 down to “finished size”. You can buy actual 2x4s, but they won’t have the nice planned surfaces or beveled edges.
I’m not wondering why it’s that sized, I’m annoyed why they insist on calling both rough saw and finished items 2x4s.
I had to go back and re-read the history of dimensional lumber. 2x4 was an actual 2x4 cut until recommendations by the Forest Products Laboratory (American Lumber Congress?) in 1919 to balance functional and economic requirements (1 5/8 x 3 5/8). It’s neither the shrinkage nor just milling after drying, they literally just cut it smaller. And if my last 20 trips to big box stores with lumber are any indication, they don’t care about cupping or warpage either.
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.
Worse still, the pattern does not continue like one would expect.
There’s just an arbitrary point where they decided to take an extra 1/4" bite out of it. I’m not sure whether that’s more of an effect of shrinkage from kiln drying being proportional to the original length or an effect of industry practice to mill smaller boards to eke out more cuts per tree.
And for the record, yes, I am aware the discrepancy is not entirely explained by shrinkage. They do a planing step after drying. But the shrinkage is a not insignificant part of it. They have to round down to the nearest convenient dimension from wherever the shrinkage stops.
If longer boards shrink more, the finished boards would necessarily have to be smaller. I question whether that’s the effect at play, though, because I believe there was a phase in the industry where that extra quarter inch wasn’t taken off, and they changed their minds about it later.
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”.
That’s not from shrinkage (well the 1/16 might be, especially newer fast heated junk at the Homely Despot). It’s from when they mill the rough sawn 2x4 down to “finished size”. You can buy actual 2x4s, but they won’t have the nice planned surfaces or beveled edges.
I’m not wondering why it’s that sized, I’m annoyed why they insist on calling both rough saw and finished items 2x4s.
I had to go back and re-read the history of dimensional lumber. 2x4 was an actual 2x4 cut until recommendations by the Forest Products Laboratory (American Lumber Congress?) in 1919 to balance functional and economic requirements (1 5/8 x 3 5/8). It’s neither the shrinkage nor just milling after drying, they literally just cut it smaller. And if my last 20 trips to big box stores with lumber are any indication, they don’t care about cupping or warpage either.
Yeah whenever I need lumber I plan to set aside at least half an hour to dig through the piles to find OK boards.
You can’t convince me that wood shrinks by 35% by crossection. No way.
Yup, that was wrong.