Filling and Sealing Joint between Tile Backer and Ceiling

[schismatic]

I’m just about to install 12.5mm Hardiebacker boards in my 3-wall en suite shower and I’m just wonder how I should fill and seal the joints with the existing ceiling (believe it is just plasterboard and painted).

What should I use for filler? Tile adhesive and then tape the joints as normal after that? Or is it better to use a Silicon sealant and then tape the joints after that?

I plan to install the boards with a slight gap (2mm) between top of board and ceiling tonallow for expansion, then fill that. Is that the best approach?

Thanks in advance.

 

[One Day]

No need to seal if it's to be tiled over.
Normally I would seal the tile-to-ceiling joint with a paintable caulk, or Silicon if already painted.

 

[schismatic]

Great, thanks buddy