I've spent the past couple days down in the basement constructing some walls for a new store room and furnace/mechanical room. I didn't want a square store room so I put a forty-five degree angle on that room so that it would open up the view of a portion of the basement. I've done this several times before but it posed a problem when it came to finishing the joint. I wanted it good and sturdy but nice and straight. I used to just cut each sheet with a square cut and butt them tight where they meet at the point of the angle. But that leaves a gap and it's hard to fill. I've used flexible metal tape for those kinds of joints and it worked pretty well but was a challenge to make it look right and be sturdy when done. I started thinking about it while constructing the wall. Here's what I came up with.
I should have taken a picture of the plain corner before putting up the sheet rock but already had one side done. I think you'll get the idea though from the picture. Where the two walls meet I put a 22-1/2 degree angle on each wall. I then ripped each 2x4 that makes up the corner with a bevel on one side. This gave me a nice clean solid 45 degree angle to work with. When I applied the sheet rock, I just ran the piece a little long and screwed it into place. Then I used my "power hand saw" which is nothing more than a scaled down sawzall. It has a nice stiff blade and it does a great job cutting drywall. I carefully laid the blade along the opposite side of the angle and cut the sheet rock at an angle. I got it fairly close and then used a small surform plane to make the edge line up nice and clean with the point of the angle. Then I applied the drywall to the other side of the angle and screwed it in place. Then I repeated the cutting procedure but laid the blade parallel with the finished side of the wall on the other side of the angle. Again I cut it close and finished with a surform. It came out very nice. Now I can apply the flexible metal corner tape over the outside of the corner and it will be nice and straight and should be pretty durable. Here's a few pictures of the process.
This is a wide shot of the room.
This is a close up shot of the upper left portion of the undone section.
This is a close up shot of the overlapped corner joint.
Here's a close up of the finished joint prior to tape/mud.
I just thought I'd share a bit of the project with you. Maybe it will help you out some time down the road if you're in a similar situation.