We are renovating our 1890 farmhouse and adding an extension to it. In this extension will be a new stand up shower for which we have bought some 12 x 12 marble tiles. The beginning of the project will be on a wood floor, but we just need to know the steps for making the right foundation and slope for the floor of the shower. The tiles are not the flexible smaller squares, but the 12 x 12 solid slabs. If anyone knows the correct procedure for this please educate us?