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.
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.