Slope of wet room shower tray

[Triassic]

I need to construct the shower tray in a wet room. What sort of fall do I need to ensure the water flows to the plug hole.

[nod]

If your forming it in a screed I normally aim for 20 mil fall 

15 minimum 

[Onoff]

My Geberit wall drain said 1 - 2%. With my wet room corner that equated to I think 14 - 28mm. I ended up at about 20mm so circa 1.5% and it drains a treat. I was worried that you would feel the slope when you walked across it. You don't. With hindsight I'd have gone 2%.