Mikey:
Every timber in a frame gets it's name by its location. A tie beam is called a tie beam because it does actually "tie" the two broad walls together.
Timbers in a wall, as mentioned are usually called girts and sometimes even connecting girts.
And most timbers do not shrink in length, very much if any at all.
It may appear that they shrink if there is a gap between the girt shoulder and the post. But most likely the post has shrunk, some.
Jim Rogers
