Designing Kitchens and Bathrooms - Greenboard flush with bathtub problems

I am aware that the greenboard that is being used around the tub walls must be overlapped into the tub flange. My problem is that the studs don't line up with the flange, so I end up with a slight slant in the greenboard towards the tub. To me this makes absolutely no sense because its impossible to tile over unflat surfaces.

My question is how do I hang my greenboard so that its level with the studs and the tub flange?

Also, I've read over 100 threads now and it seems as though greenboard should not be used around where water will be going. Is the cement board absolutely necassary or can I use the greenboard?

I found this thread (http://forum.doityourself.com/showthread.php?t=299352&highlight=drywall+flange) about the same problem as mine but didn't quite help me.

Thanks for all your help and looking forward to becoming a frequent member! :)

I would not recommend greenboard at all within a shower.

Why did you choose greenboard and not CBU?

At the time I purchased the Greenboard I did not know that CBU was the better standard. Not to worry, I didn't put up any walls yet around the tub because of the leveling problem I stated in my initial post. So, about that, should I pull out the tub and notch the studs in order to fit the lip of the tub into them to level the CBU/Durock?

You should install lattice strips over the face of all your studs in the tub area. This will build up the wall so your cbu will be square with the wall, and not force an angle as you described. Stop the lattice strips at the tub edge, or continue them along that wall if you like to give a smooth transition.

If you have tiles that are larger than 4", then you can stop the cbu about an 1/8" above the tub flange and caulk the gap. That little bit of area on the tile with no thinset will not cause any problems. On the other hand, you do not want to use greenboard unless you plan on using a waterproofing system like Kerdi. If that is too expensive then you should go get yourself some durock or Hardie. Put a min of 4mil plastic on the studs and overlap the tub flange, then secure the cbu with screws for the cbu or deck screws. The plastic is used to prevent moisture getting to the lumber since the grout, thinset and cbu will absorb water.

http://www.schluter.com/5288.aspx