I'm installing a new bathroom in my house. One of the jobs is to tile the
walls adjacent to the bath, as I'm going to install a shower attachment.

One of the walls seems to be made of thin (8mm or 10mm?) plasterboard. On
that wall, I'll be fixing a shower attachment holder. Is it OK to stick the
tiles directly onto the plasterboard? Or should I face the plasterboard
with say chipboard first, to increase the rigidity and strength?

Also, should I use a special waterproof adhesive and waterproof grout with
the tiles, or is the regular stuff considered OK for shower areas?

The tiles I bought are 300 x 250mm granite effect tiles which are almost
twice as thick as the average small 150mm square wall tiles. So they do
have a lot of rigidity and strength of theor own.

Thanks...

Al