I have recently moved here from Europe where bathrooms are constructed with masonry walls and drop in baths use siporex (lightweight aerated concrete) for the structure and so there are no issues with rot!

Now I am trying to get to grip with the extensive use of lumber and urgently need some advice....

I am building a 'wet' bathroom that has a shower immediately adjacent to a drop in tub, so the tub deck will regaularly get wet. The shower has one interior wall and one exterior wall. The drop in tub has a 2" 'lip' to the deck and a 6" 'shelf' on all 4 sides two of which butt up to walls, one interior one exterior. I intend to tile with 18" slate everywhere.

My current plan is:

For the shower:

1) build the shower pan using Noble CPE + pre-slope, reinforcing corners etc

2) staple 15lb roofing felt over the studs down to and overlapping the CPE

3) screw hardibacker board down to the shower pan

4) tile

Is this ok? What do I do with the outside wall bearing in that I have heard you should not use vapour barriers on exterior walls? Is there a better way to go with the waterproofing? Do I need worry about the penetrations of the screws that penetrate the felt and hold the backerboard to the wall studs?

For the tub:

1) Frame out the box for the drop in

2) Felt the walls like the shower and bring the felt over the deck and down the side facing the shower (as per the walls)

3) screw hardibacker to the deck and walls

4) seal hardibacker deck with redguard

5) tile (slate)

6) drop in bath on top of tile with sealant between lip and tile

Is this ok? My hope is that water on the deck will not be able to penetrate through to the felt underneath, otherwise it can only run into the void under the bath. Maybe epoxy grout would help?

Thanks for your feedback, ideas and help. Right now I am looking at this job with significant worry!

Cheers,

Steve