Space and access
Indoor saunas need ceiling height, a suitable floor and access for delivery of panels. Outdoor saunas need a level foundation and a route for freight delivery to the installation site.
Climate
Outdoor saunas in cold or wet climates benefit from a roof kit and proper sealing. Indoor saunas are protected from weather but need ventilation.
Electrical runs
Running power to a backyard sauna can add meaningful cost. Get a quote from a licensed electrician before deciding.
This guide is general information, not installation advice. Always follow the manufacturer's instructions and local building and electrical codes, and use licensed trades where required.