When your hot tub is fully occupied and filled up it is going to weigh around 2 tons. This weight means it must be placed on a solid base. It can only be placed on the decking if you have first consulted the decking company to ensure it can hold the weight. You are able to have your hot tub sunken into the ground or have decking around it, as long as airflow is not obstructed and you are still able to drain your hot tub.