A scale plan of your space is a good place to start. Measure carefully as accurate dimensions are key and include features that are likely to affect the design, including windows, chimney breasts and doors.
Waterproofing wet rooms involves priming the floor, the lower section of the walls and the whole of the wall area around the shower and then covering with a syrupy membrane. Once it’s set, the room is then tiled.
Cut out to-scale shapes of everything – loo, basin, bath and shower enclosure, for instance – and rearrange them until you find a layout that works best. Incorporate plenty of space between the elements and consider how the room will work with more than one person in there at the same time.
It’s also worth raising the bathroom door threshold by about 5mm from the floor in case the room fills with water (if someone covers the shower drain with a towel, for example). This will keep the water contained.