It was 50x100 when I was building in Chch ~10 years ago. It was explained to me that the rough cut timber was closer to the stated size, and that the finished

It was 50x100 when I was building in Chch ~10 years ago. It was explained to me that the rough cut timber was closer to the stated size, and that the finished timber we used for framing was named after the unfinished dimensions. Of course, I don't know how true that actually is. Certainly the unfinished 75x50 we used for roofing purlins (spelling?) was noticeably thicker than the finished structural 100x50s