Starting a cloakroom job on Monday, walls are all internal, fairly new house so plasterboard. 2 are half tiled, 1 of which has burglar alarm control box high up which I can't touch/don't want to move. It will be boxed in, with access.
Customer wants them all fully tiled, I will probably have to replace the walls where existing tiles are but on the alarm box wall I will have to leave the higher portion in place. I am expecting to cut horizontally, adding additional supports and fit new boards. Never done this before, would I use jointing tape and what would I use over it, would tile adhesive do or do I need plastering product? Apologies for what is probably very straightforward but don't want to mess up.
Thanks in advance.................

hi yes its best to use jointing tape over joints including internal corners and 2 coates of base coat if your tiling over dont use top coat let plaster dry out befor tiling dont forget weight limits on pb hope this helps
the reason for using tape is to join sheets together with reinforcing if you dont it will crack and more than likley that crack will carry through tiles

You may well end up not having to replace any of the wall if you remove existing tiles carefully.
If you do have to then do as you say.
No need for jointing tape as it's not a wet area.
Just prime with acrylic primer if using bagged addy.

No need for joint tape. You might need to get it re-plastered to level it out. If it was tiled with tubbed gear, you might be lucky and not have to re-board.

Many thanks guys. As a new build, doubtful they would bother with powdered, so may be lucky. Cheers.