How about putting the cement board over the whole floor then mix up some self leveling cement and pour it over the low area.
Tiling sloped floor.
Step 1 set a piece of transparent paper over the drain.
A slant slope situation might be one where over the course of 15 or 20 horizontal feet the floor slopes down one or two inches.
If there s a noticeable slope to the floor leading into the drain make sure to use smaller floor tile four inches across or less so you can more easily follow those contours.
The slope will not hurt the tile and if you preserve the slope you will also preserve the old drainage pattern of the floor.
Except for that slope the floor itself might be flat.
Once your tile is in place let it set for 48 hours.
If your floor is sloping 1 1 2 then it is really up to you whether or not to level.
Tiling an uneven floor.
You should be aware the shower floor is slightly sloped to ensure that water runs into the drain.
Let the tile set.
Floor leveling compound if the substrate the floor tiles are being installed on is uneven but structurally sound a self leveling floor compound can be used to even it out.
Follow steps for tiling a shower wall.
Slightly sloping floors which are common in older houses often worry homeowners who want to install new rigid floorings such as laminate ceramic tile or hardwood.
Leveling it may make it better for walking and furniture but if you have a leak the water will not flow like the old sloped floor.
For rooms that have a general slope the issue may be foundation problems that require the assistance of a foundation repair company or a general contractor.
Even when we think that the surface seems off it s hard to tell without a measuring tool.
For example a floor that extends 4 feet away from the drain should have 1 inch of overall slope.
Otherwise it is no more difficult to figure out how to tile a shower floor than it is to figure out how to tile a shower wall.
You need 1 4 inch of slope for every linear feet of floor space.
Step 1 check where the peaks and valleys lie.
The most effective is a straight edge a metal bar that can be.