Designing Kitchens and Bathrooms - putting in tub with surround

I've got the bathroom gutted, I know I will use drywall on most of it, but what are you supposed to put behind the area where the fibreglass tub surround (1pc) goes against the wall? CB? or is 1/2 drywall OK since it will all be covered by the surround?

thx

The last surround I installed went right against the studs.... the drywall above the surround installed against the lip of the unit.

the more I think about it that's what I thought. Otherwise you'd have to put whatever board behind the tub as well or the tub/surround would be shimmed out different. That makes it easy. Now, I'm thinking I'll try and sneak a one piece surround in here since I'm down to studs, have the door frame out etc. The width it 32" for the surround, any other problems with doing this or should I stick to 2pc? It'll save me a few hundred bucks going with 1 pc....

Nice thing about a 1 piece is... it doesn't leak....

Bad thing is... it's a bear to install...

I'm like thezster, anytime you can go with a one piece, do it. You won't have the leaks, and you'll be finished by dinner. The one pieces are more rigid, giving support where it is needed. Make sure you support your shower control from within the framing structure, and not just from the fiberglas on the tub enclosure. I have had to follow too many sloppy installers who just allowed the control to be supported by the inlet pipes and the shower head pipe. This will, however present a problem installing the one piece, unless you have access from behind the control to release it and reinstall it once the one piece is in place. That is if it is already there.
Good luck.

thanks for the replies. I've done a lot of measuring and at this point it looks like the only way I'll get a 1pc in is to cut a hole in the adjoining bedroom and slide it in. Then as you say I would have access to the plumbing for shoring it up etc. I may end up having to go 2pc though as I looks like I'd have to remove al plumbing in the wall to slide the 1pc in. Do these things come with an installation manual? I'm wondering about what order to hook up the plumbing? I'm not doing the plumbing myself, I'll leave that to the pros. But do I bring the tub in, mount it, secure it, then have the plumber do his thing? I mean, he can't really hook things up until I get the 2nd pc secured on the walls (for the shower head etc) but if I secure it then he can't access the pipes behind it. Cart before the horse sort of thing... :)