Flexing roof truss and wall causes crack?

[Eshelon]

Hello, I'm new to the forum. I was looking for a place where I might ask such a question. I'm not sure if this is the right place but here goes.

It might be better to take a picture but I'll try to describe the problem as best I can. Our living room has a vaulted ceiling. The hallway that connects to it obviously isn't. Where the hallway and the living room connect there is a wall. Where the top of the wall seams with the vaulted wall (going up to the ceiling) a horizontal crack appears, along the top of the wall, below the vaulted portion of the wall. I've patched and painted, patched again, painted.. I guess the wall and the ceiling truss do not expand / contract the same and so the crack appears. Any advice?

[concretemasonry]

Nothing you can do because of the angles and weather (temperature, humidity) conditions. You can minimize the annual movement effects if you have the commonly recommended "floating joints". If not molding can hide the signs of movement.

With wood, you are dealing with a building material that is really not stable.

[Eshelon]

I'd like to learn more about this "floating joint".