I'm n the process of having my 1 1/2 story house upgraded to two stories. One of the things that isn't changing is the floor area where the bathroom will be located. The floor in that area has always had an inward slope. When I use a level I find that the drop is 1.5 to 2 in over the 6ft or so of the slope. After that the floor levels out.

Given the fact that I already have a slope I was thinking it might be a good idea to put in a zero entry shower with a trough drain on the wall at the bottom of the slope. I'm here today to try to get an idea of what this would entail. I have seen kits and looked at videos on the creation of zero entry showers. But they all start with the premise that the floor is level and therefore the slope needs to be created. Since I am starting with a slope I am trying to figure out where to start on the process. I figure I may have to manipulate the slope a bit in places (like on the far side of the drain since I don't think it should go right against the wall) but my main concern is the "layers" that I will actually need. Currently my plan is to use a floor patch/leveler over the whole area to make sure my slope is correct all the way around. Then to use a paintable waterproof membrane as my waterproof layer before putting on the thin set and the tile floor. What has me most confused is will this be enough to waterproof the area. Any advice would be greatly appreciated.