How to Build a Good Sauna

Pre-Sauna Construction Planning

Sauna manufacturers provide good instructions about how the sauna package shall be installed, and what is required from the set-up, space, frame, insulation etc.

But as also explained in “How and Where to Buy a Sauna” section, it is very important to plan for the location, size, shape and access as early as possible. This pre-sauna construction planning step is unfortunately often neglected, making less desirable the usability of the sauna and the overall comfort level of the sauna. Not all architects understand the nature and the basic physics of the sauna room, either. So, it is strongly recommended that a sauna manufacturer or dealer will be contacted in the initial design phase of the house, addition, upgrade or e.g. basement finishing project.

Insulation of the sauna room is important, with the ceiling being the most critical location to insulate well. Regular fiber-glass insulation plus an aluminum foil vapor barrier should be used.
Electric heaters should be sized according to the size of the sauna. All UL-listed heaters have specific size ranges within which they safely operate. Heater kilowatt sizes typically range between 1.5 kW and 15 kW, and the respective breaker size varies between 15 and 60 Amps. Always read heater instructions and use a licensed electrician for wiring. As part of your pre-construction planning process, it is advisable to have an electrician verify your breaker panel has enough power is available.

Use only UL listed heaters!


The UL Safety Standard (UL 875) requires the maximum sauna temperature in the US not to exceed 195 F. All the UL listed heaters or sauna units follow this requirement. Higher temperatures are possible to reach saunas equipped with wood-burning stoves, but it is advised to not to exceed this temperature level regardless what type of heater is used.

Where to Build

Three primary factors usually determine the location of a home sauna: physical space available, proximity to a shower (existing shower or new shower as part of the sauna suite plans), and proximity to a cooling off area. (Please also check the “design guidelines” page). The most typical set-up for a sauna in the US is in connection to a home gym, typically in the basement (if such exists). Another popular and convenient location is a master bath suite, space permitting. Other possible set-ups would be in the garage, in a converted spare bedroom, in a finished or unfinished basement without a gym. With America’s fast growing interest in backyard living, outdoor saunas are becoming more and more popular—near a pool, on the pool deck, on a patio, or simply nestled somewhere in the backyard landscape plan.

Free-standing saunas can be located in almost any space. However, what follows below about the basics applies them, too.

Basic Requirements

A sauna needs a space which is preferably 7 feet high, has a smooth and level (unless drainage is used) waterproof floor. The floor can be tile, concrete or vinyl (not carpet!). To best utilize the space, and to get a balanced temperature level, the shape of the sauna room should be close to a square, or e.g. 6:4 ratio between the wall lengths. The best location for the door (swings out!) is on a longer wall. If space allows most sauna users like to have the option of lying down in the sauna. A 6’ wide sauna, or greater, is recommended for lying down. Sauna designs typically maximize the upper bench length by putting the main upper bench along the longest wall. Manufacturer’s websites nicely illustrate many of the most common sauna layouts and all offer free CAD design assistance.
Basic Requirements continued
The sauna room needs ventilation; incoming and outgoing. Good ventilation is one of the most commonly over-looked sauna design features. A good ventilation system insures adequate amounts of fresh air in the sauna—which in turn makes the sauna feel much more open, much more comfortable and helps users avoid the sense of light-headedness.
Though there are several ventilation options, the most common guidelines advise for the air inlet (typically about 4” x 6”) to be located near floor level on the heater wall (often just below a wall-mounted heater), and the outlet on the opposite wall just below the upper bench.

What is the Right Size for a Sauna

If you have a choice, don’t make it too small. A good size for an average two or three person sauna is from 4’ x 6’ to 5’ x 7’. Depending on the number of users and the set-up, the sizes can go up to 12’ x 12’, while also one-person 3’ x 3’ saunas still work. Public saunas are usually at least 100 square feet in size.

What Else?

A shower should be located nearby, if not even in the same specific area (master bath suite). Access to outside of the house (back yard, porch, balcony…) is a good plus, as well as a window. Glass doors and inside window panels give natural light and prevent any claustrophobic feelings inside the sauna. A drain inside the sauna room allows a more freely use of water, and makes cleaning of the sauna easier.