A roll-in shower has to meet ADA criteria to qualify as suitable for those with mobility issues. It must be 60 inches in length, 30 to 36 inches in depth, and have a threshold no higher than 0.5 inches with a beveled edge or 0.25 without a beveled edge.
The showerhead should be adjustable and extendable, while the seat needs to be no higher than 17 to 19 inches for comfort and a minimum of 27 inches from the shower controls.
The controls need to be 38 to 48 inches from the ground, and the grab rails must extend the length and width of the shower on the walls without a seat.