I have a shower Room with a very large shower tray which is accessed with two steps. These are wooden and tiled with marble chip / tiles. The problem is the top step gets very wet. It normally runs off back into the shower tray but every year I have to re-grout them because it cracks. But this year the two layers of 12mm plywood under the tiles has gone soft. So I have taken the tiles off and the plywood and want to replace with concrete.
It's only 790mm x 510mm x 150mm deep. I've got building sand and OPC.
1) But mixture shall I use?
2) I dont want to use gravel, do i need it?
3) and finally should I paint the wood first or something else?
Thanks for your help.