Shower trays tend to come in two types, the classic chuncky design that have a large lip or the low profile trays which are often around 40mm high or lower. Most showrooms and bathroom catalogues tend to show low profile trays in their designs simply because they look great. Having a low profile tray creates a sense of space in the room as well as the face that it is nice not to have to step up into the shower.
Can everyone have a low profile tray then? Well the answer is yes and no. Yes, everyone can have the tray but not everyone can fit it directly to the floor. Low profile trays can only be fitted where there is access to suitable drainage and that the drainage runs inbetween floor joists. It is NOT a good idea to start drilling holes in your joists to accomodate drainage pipe so that it runs across the joists.
You will note that the bottle trap needs plenty of space both beneath the tray and around existing joists. You should also ensure that the trap has a high flow rating and that it can be easily maintained.
So what happens if your floor joists run in the opposite way to the drainage pipe? In this scenario you would have to raise the tray using an upstand kit. This raises the tray by around 100mm which allows space underneath for the trap and associated waste pipework.