branded/sts construction boards
The Construction Board being water-resistant, more impact resistant and fully A1 fire-rated, it is a product that can be used instead of plasterboard and gives. Construction Boards will lose some strength when wet. Multiple tests have been carried out which included a pull through test at control.
https://s3.dualstack.us-west-1.amazonaws.com/kerakoll.grout/kerakoll-grout-for-porcela.html