Indoor Sauna in a Garage, Basement or Spare Room

Indoors you don't need a slab, but you do need to check the circuit, the floor, the ceiling height and ventilation. A garage often has a 240V circuit or a panel nearby. A spare bedroom almost never does. The electrical guide has the specifics.

Garage

A garage is the easiest indoor spot: concrete floor, often a 240V circuit for a dryer or EV charger nearby, and no carpet to worry about. An unheated garage gets as cold as outside in winter, so size the heater as you would for an outdoor sauna and take the bigger heater if you are in the overlap. The heater size calculator does the math.

Basement

Basements usually have a suitable floor and are often close to the panel. Check the ceiling height first. Sun Home's placement notes for the Solstice list three things to measure before ordering: the footprint plus clearance (at least 4 inches on every side and 12 inches above the roof), the delivery path for the crated panels, and the floor. The delivery path is the one that catches people with a narrow stair turn.

Basements also tend to be damp. A traditional sauna with steam adds moisture every session, so plan for ventilation and don't box the cabin tightly into a corner.

Spare room or bedroom

A spare room is a good fit for infrared. Infrared cabins run cooler, and many install on existing flooring; Almost Heaven says so for its Hinton. A traditional heater with steam is harder on carpet or hardwood, which is why makers sell floor kits (Almost Heaven's indoor floor kit starts around $529).

The smallest traditional option