Just completed the demolition of the old ceramin tile and backing board of out bathtub surround. Went to Home Depot and bought my 1/2" Durock and screws.

The bathtub has a flange on it and I would prefer to mount the Durock on top of the flange. We are going to use RedGuard for our moisture barrier.

I really dont have to hang the Durock over the tub flange and have to ferr out the walls. In doing this when 1/2 durock, the thinset and the 1/2 travertine will cover the majority of the tub surround and I could potetially have to adjust plumbing as well.

Any reason I can't mount Durock to the studs and butt it up against the top of the tub flange.

Run it down to the top of the flange, fill the gap with silicone and continue with redgard.