My folks are wanting to make their home more accessible for my eleven year old niece who is confined to a wheelchair. We're beginning an expansion of their masterbath that will help significantly. Part of the new bath will be a large walk-in shower. They would like to incorporate a curbless design so the floor of the shower will be flush with the floor of the bathroom. The main question is whether this will be possible to do. I know in new construction they make the slab lower than the slab in the rest of the house in order to accomodate the shower pan. Any resources on how this can be accomplished with existing construction would be greatly appreciated. Water and drain lines are beinging moved so some cutting of the foundation is already being planned. Let me know ya'll's thoughts on this.

thanks