Ha! It works! You can see the gap left in the drywall where the joint will go. What will fill this joint? Something that looks like this:Several companies make expansion joint covers; this one happens to be by Watson-Bowman. You can kind of see inside it on top how it looks like a "W" in plan, which allows it to expand and contract in place while being attached to both sides of the joint.
But this is below the ceiling. What's happening above the ceiling?
In this case, they just kinda come together. Again, if this joint isn't in a rated wall, then the drywall-over-the-gap should suffice. If it is rated, then we need the cover piece all the way up here. The light stuff you see in the joint is insulation. What's going on on the roof, on the other side of this gap? I think you've seen the photo before....
The leg on the left of this joint is what we're seeing the underside of in the photo before it (if that makes any sense on a Saturday afternoon).
Okay, I think I've beat this topic up quite enough. Next week's DoW will tie in with something that BaxterWatch has explained on her website. Blogging in Stereo: can you stand it? Only one way to find out...!