When I built my house, I left a drain stub to install a shower in the basement. I would like to install a large shower space which I will tile. I'm wondering how to best prepare the base. Do I need a copper pan or can I just install the cement board on the walls, flash where the board and floor meet and create a mortar base which I will tile over. I'd appreciate a referecne to a site which details my options. Commercial shower bases are not of a size I would like to use.