Pictures Joining different thickness plasterboard and tile backing board

[schismatic]

I'm currently redoing my shower. It's a 3-walled shower enclosure and so far I've removed the old tiles and water-damaged plasterboard which was there previously (15mm British Gypsum plasterboard). It's a new build house (2006) and I'm now left with the metal studding (think it's again standard British Gypsum 'C' shape stuff) (see attached photo).

I intend to put up tile backing boards as the replacement walls, attaching them to the existing metal studs and I need to have the new walls join/butt up against the existing plasterboard so that they are flush. Outside of the existing shower cubicle the rest of the room is also tiled and I'm retaining those, so the new walls need to finish flush with the existing 15mm plasterboard upon which those tiles are mounted.

My issue is matching the wall thickness of the new tile backing boards with the existing 15mm plasterboard. I was going to use Hardiebacker 250 (6mm thick) originally, however if these are flush with the existing 15mm walls then I will then be left with a 9mm gap between the tile backer board and the metal studs.

Would I be ok to put up 9mm thick batons horizontally between the existing studs and then mount the 6mm Hardiebacker on these?

If this is a good way to do it, how many batons should I use, how wide (height-wise) should each one be, and what material should I use? (ply or hardwood I was thinking, seeing as it shouldn't see a moisture environment after sealing properly and tiling)

In the close-up attached photo you can see the tiles on the right-hand side mounted on the 15mm plasterboard and the metal studding where the shower walls will be. That is on the right-hand side in the other photo looking straight on.

 

[WetSaw]

6mm is for overboarding. 12mm for stud work.

 

[Waluigi]

There’s a reason that the metal studs were clad in 15mm board rather than the conventional 12.5mm- for strength. In fact over in Germany it’s expected to double up the 12.5mm board when using metal studs.

When using 12mm tile backer boards, manufacturers often suggest 400mm centres of studwork. 10mm Board is 300mm centres.

For me, if it’s just a domestic shower and if the tiles aren’t heavier than 32kg PSM, I’d use 15mm PB and tank it.

 

[Boggs]

15mm plasterboard and tanking.

 

[schismatic]

Thanks for the replies.

What’s the best approach for tanking?

Also, what’s the right approach to fill and seal the join between the old and the new plasterboards?

 

[Waluigi]

I’d pop some paste on, either Tilemaster or Ardex.

Joining the two boards- tape it up and tank over it.

 

[Wayne Brown]

This is how I do it 12mm Hardibacker fix strips of ply to the studs to make up 3mm difference first . Kop

 

[schismatic]

Wayne, do you treat the ply in any way? Some sort of waterproofing? How wide are the strips?

 

[Wayne Brown]

Use marine ply bud no need to treat it 100mm wide strips will do cheers kop