The coolest spot in the sauna is the floor (70-85°F or 21-30°C) so heat loss, insulation and heat-proof floor coverings are not very important. It is quiet uncommon that the floor temperature climb to 85°F (30°C). And you may choose among many possible designs in floor construction to suit the sauna location.

▬ Concrete, waterproofed with sealer and finished in ceramic tile is the best sauna floor option.
 
▬ In case the floor is currently covered with vinyl tiles, they can be left as the heat at floor level will not affect them.
 
▬ Seal well large plywood floor areas at all joints and sealed with several coats of wood preservative. 
 
▬ Use ceramic tiles, fiberglass or seamless sheet vinyl and waterproof adhesives to completely waterproof a wooden floor. 
 
▬ Do not use linoleum with a characteristic odor.

Drainage

It is optional to use a floor drain in a home sauna. Today many of the pre-built saunas are installed in locations without drainage. Although the water that splashes on the floor will quickly evaporate anyway in the dry heat of the sauna, excessive use of water must be controlled anyway.