Hi, we expanded our house some time ago. As a result the bathroom window had to be annuled since it didn't face outside anymore. The window is located in the shower wall which is tiled; we could not get tiles to match the color of the original tiles so we decided to convert the window into a niche for the shampoo, soap etc. Now my question is: how do we build the box?, do we have to build a frame first and then put cement board and waterproof it and then tile it?. We want to make it look like that box was there on purpose and it was never a window. Thanks for any advise or ideas.