Tub surround question

Hi. I'm new here on this forum . I've been pulling my hair out with indecisions, so I thought I'd ask here. I gutted out my bathroom, and am installing a new tub and using a 5 piece tub surround. My questions are ,

Can I install greenboard first,place in the tub and attach to studs, then install the surround? Or, do I install the tub directly to the studs, bring wall board down to flange of the tub, then cover with the surround? I feel this isnt right because the flange obviously isnt the same thickness as the drywall.Some guy told me to bring the board over the flange and caulk.??? A correct procedure using the surround will be appreciated! Is the a vapor barrior needed behind the green board? Thanks in advance!!

I have never replaced a tub with pre fabricated tub surrond walls. But, i would think the installation would be much the same as with any other standard tub surround materials used tile etc. As a good practice i checked with some contractors/tile setters/masons and the vapor barrier they suggested that i use for the surround was roofing felt paper i affixed to the studs. However, some said the vapor barrier is only needed at the one block exterior wall where this bathroom i remodeled was located. Then the tub is set in place attaching the tub at stud locations (most tubs come with attaching clips) and plumb up the tub drain. Run your green board,and where it meets the tub flange it might bow in after attaching the board...keep a level handy to check how level the board is and for high and low spots that if unacceptable can make for a wavy tub surround wall.In which case you might have to fur out the studs as necessary to make for a flat level wall to fasten your board to ,and adhere your pre fab walls to.

Yes, tub goes in first. Connect the waste and overflow then do the board. Use a VB on outside walls only. The green board will not overlap the flange of the tub. Before the panels go on, fill this gap with silicone. The panel will go to the tub surface. This makes for a nice, thick seal.