A DIY infrared sauna is a genuinely different build from a traditional one, and in most respects an easier one: no stove, no stone load, no chimney and no clearance envelope around a hot appliance. What you are really doing is building a small insulated room and mounting bought panels in it correctly.
What you buy and what you build
Panels, a controller and usually a wiring harness come as a kit from the panel maker. You build the enclosure: framed and insulated walls, a foil vapour barrier, cladding, benches, a door and the lighting. Because the cabin runs cooler than a traditional sauna, the build is more forgiving, but the vapour barrier still belongs on the warm side.
Panel placement is the design
This is where a self build wins or loses. Panels behind the bench only warm your back. Plan front, side and calf or floor coverage before you frame, because the panels have to sit flush in the cladding and the cable runs have to reach the controller. Mark it all out on the studs first: retrofitting a front panel means taking cladding off.
The wiring
Panels are mains appliances in a warm room. Use the maker's harness and controller rather than improvising, keep the driver and any transformer outside the hot enclosure, use heat resistant cable for anything inside, and have the supply circuit installed by a licensed electrician. This is the part of the build where saving money is a bad trade.
Whether it is worth it
Against a prefab cabin, a self build wins on fitting an awkward space and on using better cladding for the money. It rarely wins on outright cost once panels, controller and timber are added up, and you take on the warranty risk yourself. Build if the space demands it or you want the job; buy if you just want the sauna.
Questions people ask about diy infrared sauna
Can you buy infrared panels separately?
Yes, most makers sell panel and controller kits for self builds. Buy them as a matched set rather than mixing a controller with panels it was not made for.
Is a DIY infrared cabin cheaper?
Not usually by much once panels, controller and timber are counted, and you carry the warranty risk. It wins when the space is awkward.
Does it still need a vapour barrier?
Yes. It runs cooler than a traditional cabin but it is still warm and humid inside, so the foil barrier goes on the warm side.