Designing Kitchens and Bathrooms - Stopping drywall/starting backerboard for tiling shower

Howdy-

I removed the old tile/backboard from my bathroom and realized that the edge of the backerboard wasn't located at a stud. I've included a link to a drawing:

http://i157.photobucket.com/albums/t65/chrisatunc/DrywallinBathroom.jpg


My desire: I'm going to install 1/2 backerboard and retile the show. I only want to make the backboard wide enough for the tub plus 2" or so for the egde tiles. The existing 'hole' is larger than my tile plan, so I assume I'll have to make up the difference by redoing all the drywall, too.

Questions:

1) Should I sister a 2*4 stud to the 2*4 at the edge of the tub and have the drywall end on the sistered stud?

2) OR should cut the hole bigger to the next stud to the left (see picture) and take the backerboard out to that next natural stud? That would prevent me from having to redo rest of the drywall along that wall. I wouldn't tile all the way out there, so it's a matter if whether or not painted backerboard would blend well enough with existing drywall. I know it wouldn't look perfect.

3) do I tape the joint between the backerboard and the drywall? I'm thinking
'no' and instead use silicone caulk at the seem after I've layed the tile.

Thanks!

Chris

#1 - yes

#2 - no, you would have to finish the backerboard similiar to plaster to have a chance of it not being noticable.

#3 - usually this joint is under the tile

Great, thanks for the reply.

Even if the seam of the drywall/backerboard is under the tile, would I tape that joint or just make sure the joint is filled (with mud) before I start the tile job.

-Chris

I'd fill the joint with thinset, durabond would also be ok.