As per BS 5385, the maximum weight restrictions for wall substrates are:
Gypsum plaster: 20kg/m2
Gypsum plasterboard (12.5mm thickness): 32kg/m2
Sand and cement rendering: 64kg/m2
Lightweight foam-cored tile backer boards: 60kg/m2
Glass reinforced cement-based boards: 50kg/m2
Gypsum fibreboards: 40kg/m2
Other rigid tile backer boards: Consult manufacturer