Greetings, I am not sure if this s/b in this section or in construction, so I will post it in both.

We are adding a whirlpool tub to our bathroom addition and it requires a tub deck.

The exterior walls are all framed and insulated (Icynene).

Should I rock the walls first and then build the support deck on top of the drywall? (Hopefully this is the right way as the wall is already rocked).

OR

Should I cut out the rock to attach the framing members directly to the studs?

Should I have used cement board instead of drywall? (The drywall is DensArmor Plus if that makes a difference)

Now for the shower enclosure. I am forced to use a mudbed as I can't move the existing drain. So...

For the walls, should I use an EPDM membrane behind the cement board (hardie board)? I have found a good link for how to build the mudbed for the shower pan which will use an EPDM membrane.

As always, thanks for your help.

Dan