I am in the process of renovating a very large house and converting it into 5 flats and in two of the flats I am hoping to build a wet room style shower area and what I am looking for is a recommendation of a product to fit on the floors to create the waterproof sub floor before the tiles are laid. I have looked at a system called Wedi Board which is like a foam panel with a cement impregnated coating which is cut to size and screwed down with washers and screws and then the joints are taped and filled etc, but what I really want is to have a one piece floor ' tray ' or similar and therefore less chance of a leak. I have had a suggestion that there is a one piece copper layer on the market that is laid and the edges are rolled up the walls and the tiles overlay this but have not been able to find a UK supplier. The shower areas are about 1.5m X 1m being rectangular in shape with a raised step into the room of around 5" to form the water barrier. Any advice or suggestions are welcome. Thank you.