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Building and insulating a sauna

Building and insulating a sauna isn’t especially complicated, but there are some things to bear in mind to get a perfect result.


Building an outdoor sauna

Building a sauna is usually done in two different ways and the most common is to buy a sauna kit or to let a professional company build the sauna on site. The biggest advantage of buying a construction kit is that it can be completed in a few hours (feel free to get help from some friends). Before you start building your sauna, it's good to know the following:


In the picture you can see Sauna Oscar

There are different criteria to consider depending on whether you build the sauna outdoors or indoors. The biggest advantage of building a wood-fired sauna is that you can place it virtually anywhere. Create a magnificent view, place it close to a lake or build a floating sauna. You decide!

Building an indoor sauna

Building a sauna or a  sauna room  indoors doesn't usually require planning permission (in Sweden), as long as the sauna doesn't affect the exterior of the house.

In the picture you can see Sauna room Hasse

How much does building a sauna cost?

The price for building your own sauna depends entirely on the type of sauna you want to build and the conditions. Buying a sauna kit is usually both easier and cheaper than hiring a professional to build one. You can of course build it all yourself to keep the costs down but it's not something we would recommend for a beginner.

When you buy kits from Polhus, you can count on these approximate costs:


The first step in building a sauna is the sauna insulation. It may seem unimportant because the room is small and only heats up sporadically, and it heats to such a high temperature that you might think a few millimetres of insulation material don't matter. But by being meticulous with the insulation, it's faster to heat it up and the temperature will stay at an even and comfortable level more easily.

When you build your sauna, you should put 45-70 mm (1.8-2.8 inches) insulation in the ceiling (for a free-standing sauna) and preferably both in the ceiling and walls for an indoor sauna. Glass wool is the best material to use. It's non-combustible, keeps its shape and is easy to work with. On external walls, there must be at least a 20 mm (0.8 inches) air gap between the sauna and the external wall. The same goes for the ceiling.

Choosing the sauna heating

There are two different types of sauna heaters that you can choose from. They have different advantages depending on whether you’re building a free-standing sauna outdoors, indoors or against the house wall.

Wood-burning sauna heaters

If you build your sauna outdoors, there's nothing that beats the feeling of a classic wood-burning sauna. This provides a more even heat but requires a chimney and masonry.

Electric sauna heaters

These are suitable for building a sauna indoors, e.g. in the basement. The fact that it is powered by electricity and placed indoors makes it easier to use the sauna throughout the year. All it takes is a push of a button to get started. The ouptut of the unit is determined by the size of the sauna. The larger the sauna, the more powerful the heater needed.

(Combi heaters)

These function as both dry and steam sauna heaters, depending on whether you choose to use water to increase the humidity.

Choosing the panel

Different types of wood have different properties. In addition to the difference in colour, they absorb heat differently, which is something you want to avoid. It's the room should be warm, not the walls. For the benches, you also want a knot-free material that's comfortable to sit on, such as alder or aspen, but there's nothing to prevent you from mixing materials in the sauna and, for example, having one type of wood in the walls, another in the ceiling and a third to sit on.

Sauna doors

For safety reasons, a sauna door should always open outwards because the moisture can cause it to swell and it's easier to open it outwards than into the room. In addition, it should preferably be on the same wall as the sauna heater, to optimise circulation.


It may seem like the wrong tactic to ventilate the air in a sauna, where you want to have time to heat it to a really high temperature first, but to get warmth in the sauna the air needs to move.

The air valve should be placed far down, as close to the sauna heater as possible. The outgoing vent should be high up on the wall or ceiling on the opposite side, i.e. at the maximum distance from the intake air valve. The valves must be the same size and open into the same space for optimal ventilation.

Sauna interiors

There is a huge amount of sauna equipment and sauna accessories you can buy. Benches, thermometers, rods, buckets, brushes, hangers, chairs and ornaments are available, but a good rule of thumb is to leave the interior clean and practical.

When you build your sauna, you should place the benches so you don't have to step over each other when you go in and out, and keep the decorations to a minimum.

If you have any questions or problems about building a sauna, feel free to contact our construction experts who can help you with all aspects of your project.

Related to building and insulating a sauna

Polhus Sauna Cabins/Sauna Houses

Polhus Sauna Rooms

Polhus Barrel Saunas

Polhus Sauna Accessories

Installation of the Sauna Heater and Chimney

The key to a good foundation