preferred waterproof barrier for tile tub surround

What is the best waterproof membrane to use for a tile tub surround? I plan on concrete backer board over fiberglass-insulated studs, but that is not a water barrier. Surely some of these membrane products are better than others. Anybody care to point out the proper layup so I may get this right the first time?

The tub is enameled cast iron, if that makes a difference. Floor will be tile too. Glass tub doors are planned.

Now you did it...... You will never hear the end of this story!!!!!!!!!

Might as well throw in putty or silicone......... copper or pex............

I personally like Laticretes Hydrobarrier for hops.You need to use fabric(you should with all liquids for that matter)ofcourse,in all transitions and change of plane.

I prefer this liquid for this circumstance because it is very light blue,and enhances visibilty in a typically dark area.This can be a problem with other darker liquids when trying to follow levelk and plumb lines.Also,the price is very affordable.

Hope this helps

Thanks for the tips. Good point on weighting the tub with water, although I did not see attachement points on the cast iron tub to fasten it to the studs.

Need some clarification..on weight ballasting the tub.
Are ya'll advising to ballast the tub full before putting the board on ?

The joint between the CBU and tub, so you *lift* the nobleseal, bond the membrane to the tub and then liquid away including liguid in the joint.
Or if I'm reading this right, you use mesh and thinset on the CBU, leaving the mesh *open* in the joint - in which the liquid membrane interlocks with the mesh that is hanging above the joint....

The tub when full of water might deflect, or sink a little. So, since you don't want your waterproofing to be stretched and pull away, creating a gap, if you fill it so it's down as much as likely ever to be, then install the waterproofing, as long as the joint is flexible, it will remain intact.

Got it. Picked up the flashing detail on the old *wood window in bathroom* thead awhile back.

Interesting read on locking in the tub. Any tub for me is going to be CI. Nothing else.
What's the point of a non CI tub when you lose the heat.

I suppose mortar on the legs might help but between the weight, and the ledger board, it's fairly snug.
I don't set tubs for a living so what do I know..

Screws/fender washers to the flange to lock in the wall. Never read that before.
I'm assume you are using SS hardware. Must be a #10 or #12 SS screw cause anything smaller than that is too brittle.

IF your floor is nice and level, a CI tub doesn't need anything underneath it, as it is not going to deflect. If the tub has feet, and it doesn't sit flat, you can either shim it, or set the whole thing in piles of mortar. Mortar is often used for two purposes: leveling, and support (important for less structurally strong things like fiberglass and acrylic tubs or shower bases).