You need to isolate the room thermally. Insulate the floor, cieling and walls. You need to consider the envirornment when selecting the refrigeration equipment. The best floor, and cheapest, it to frame it up with wood, put down tar paper and waterproofing shower pan goop. You can then tile right over this and use a polyurethane sealant to fill the wall gaps and cracks. I assume you are using a walk in cooler?