Drain Placement and Floor Slope
Fall Is Not Negotiable
A shower floor needs a consistent slope toward the outlet across its whole area, with no flat spots and no reverse falls at the edges. Standing water is what stains grout, grows biofilm and eventually finds a weakness. This is measured with a level during construction rather than judged by eye afterwards.
A Centre Drain Means Four Planes
With the outlet in the middle, the floor falls from every side toward it, which means the tile has to bend across four sloping planes meeting at diagonal lines. Small format tile or mosaic handles that easily. Large format tile does not, because a rigid piece cannot sit flat on two planes at once.
A Linear Drain Means One Plane
Put the outlet in a channel along one edge and the whole floor becomes a single sheet falling in one direction. Large tiles work, the floor can match the rest of the bathroom, and the visual break is a single line. That simplicity is why linear drains have largely taken over, and it is a plumbing decision made at rough in.
How Much Depth Is Available
Fall requires depth, and depth is whatever exists between the finished floor level and the structure below. On a concrete slab, achieving it usually means cutting the slab to drop the trap and the branch. On a suspended floor it means working within joist depth without cutting anything structural. Establish which situation applies before drawing the shower.
Curbless Needs Planning, Not Just Willingness
A level entry needs the shower floor recessed relative to the bathroom floor, which is a structural adjustment, plus enough fall inside the recess and often a longer linear channel to keep water in. It is very achievable and it is not a decision that can be made once tiling has started.