When looking at the height of the shower walls consider two measurements.
Wall mounted shower height.
If you are considering using a standard wall mounted shower head use a shower head height with measurements ranging from 80 off the floor or 6 to 8.
Inside the shower the height from the drain to the top of the wall needs to be at least 70 inches.
The shower wall should be at least 72 inches in height from the bathroom floor outside the shower inside the shower the height from the drain to the top of the wall needs to be at least 70 inches.
The top of the seat must be a minimum of 17 inches and a maximum of 19 inches above the shower floor.
This allows patients to be raised to a comfortable working height that wont strain the caregivers spine but also lowered for easier transitions onto and off.
The requirement for seat height however is very simple.
For those using rain shower head it will require you a 4 5 or 8 height while handheld shower head is best if fitted with 36 to 72 hose pipe that can also be mounted.
The ada provides detailed requirements for shower seat design and placement including clearances between the seat and the shower opening between the seat and the shower wall.