No, a floor drain is not common in a sauna
Of course, if you are planning to take a cold quick rinse in your sauna, then yes, you will want one.
Adding several ladles of water to your heater or to the walls is fine
Yes, we encourage our sauna customers to add water to the HOT sauna rocks one ladle at a time. Sometimes, mixed with eucalyptus. Helps open the lungs and the steam will warm you to your bones and it just feels good.
Also, a little splashing in the sauna is fine. It’s common in many sauna cultures to throw water on the walls too. The cedar will quickly dry it out. Cedar is very porous — increase the humidity in the sauna room.
If you’re concerned about moisture remaining, then leave the sauna heater on an extra 20 minutes but you’ll see saunas contain the heat very well. All the moisture will evaporate in about 5-10 minutes. Sometimes, right before your eyes.
Some of our customers have installed indoor sinks with a drain in the wall too!