For precuts, you may need construction help. With these, you provide the wall studs, insulation, and exterior walls, and then must build the unit from precut pieces. A precut kit typically includes wall and ceiling boards, assembled benches, a pre-hung door, floor decking, a sauna heater, and a variety of accessories, from back rests to heater fences, vents, and controls.

Major manufacturers may modify their precut kits to accommodate custom sizes. From your blueprint or floor plan, they will custom-size a sauna to fit any space—even if the design includes curves and angles, or just if you want dramatic windows. But unless you’re working with an odd space, custom- made saunas aren’t usually necessary because many sizes and configurations of both precut and prefabricated standard kits are available and are less expensive.

Modular or prefabricated saunas cost a bit more than precut kits but are much easier to erect. Because of the labor savings, total costs are similar to precut saunas—and you can have one installed (or do it yourself) in half a day. If you move or want to relocate the sauna, you can take it apart and reassemble it somewhere else. They have two-sided, pre-insulated walls and ceilings that simply lock together. Benches, back rests, and floor decking are all pre-assembled.

For example, Harvia makes a prefabricated system that has 1-by-4 clear cedar or vertical-grain redwood on the interior and rough-sawn fir on the exterior. Between the two surfaces are 2-by-2 wall studs and R11 foil-backed fiberglass insulation. Other options are also available—for instance, you can get rough-sawn Douglas fir plywood exterior or an imported sauna that is built from Nordic spruce logs.

The concept of prefabricated modular saunas is the fastest growing part of the sauna business. Precuts represented about 90% of sales until recent years; now choice is gravitating more to prefabricated saunas. Although prefabs once were just square boxes, now designs of prefabs are handsome and contemporary with deluxe interiors, low-voltage lighting, interesting angles, and plenty of glass.

Finlandia offers a complete, insulated outdoor sauna, complete with roof package; available in 4-by-4-foot to 8-by-8-foot sizes, it is designed to be assembled on an existing slab.

Taking the prefabricated concept to its ultimate conclusion, the Helo Porta-Saun and the Finnleo Thera-Port come complete in just two pieces that you can lock together in a couple of minutes. These are popular “portables” for people who live in apartments or condos.