cement fibre board: inside/outside corners and tanking question

[jugglesm]

Hi all, I'm just finishing off the stud wall for my first ever wet room.  I'm using 12mm STS construction board and hoping to construct an alcove within the stud to house showergel/shampoo bottles.  Couple of questions:

 

1) Can I just butt STS at 90 degree angles to create my inside and outside corners? or do I need some form of angle bead?

 

2) Should I just tank the floor joints or do I need to waterproof the cement fibre boards floor to ceiling? if so what product should I use and is taping joints necessary?

 

Many thanks for any help

[Conor]

Not an expert on the boards you are using but we used plasterboard. Just fitted as normal, we're taped and filled, the used a mapai tanking kit. You have to use tape on all the joins and corners. Floor to splash height all round. Then two coats of tanking paste. 

 

I left the tiler to do the alcove as I didn't have time... I don't think he did a good job as looks like the ply underneath is getting wet and swelling. Alcoves really important as you'll have water sitting their for hours.

[jugglesm]

thanks, interested in any more advice on this particularly specific to cement fibre boards