Sauna floor: selection, insulation, and materials


Choosing the right sauna floor is crucial, both in terms of aesthetics and functionality.

The sauna floor must be heat and moisture resistant, and designed so that it can be walked on barefoot without the risk of slipping on wet feet.

There are no other water sources in the sauna as it is a ‘dry’ sauna, so it may seem that the floor can be made of any material.
In this article, we will suggest what type of flooring should be found in outdoor and domestic saunas.

Wooden floor in a garden sauna

Wooden flooring is a classic choice in Finnish dry saunas, where the emphasis is on natural materials and aesthetics. Here are the key aspects of a wooden sauna floor:

  1. The most commonly used timbers are pine, thermos and spruce, due to their durability and temperature resistance.
  2. To ensure adequate strength and insulation, the boards should be no less than 25 mm thick.
  3. An important aspect is to allow ventilation of the floor from underneath to prevent moisture build-up and rotting. In the case of a closed foundation (e.g. ribbon type), adequate air intakes are necessary.
  4. Regular maintenance and proper care of the sauna floor are key to its longevity. In the case of wood, proper ventilation must be kept in mind.
  5. In traditional Finnish saunas, no additional thermal insulation of the floor is used. However, it is important to heat the sauna well before use and to dry it after.
  6. A garden sauna may require additional protection from weather conditions such as rain or snow. This can be achieved by applying suitable protective measures to the wood.
  7. Special wooden floor mats can be used to enhance comfort.

A wooden sauna floor, properly made and following the above rules, will ensure long-lasting use and will retain its aesthetic and health benefits.

Sauna floor 26mm

Insulating the sauna floor

When building a traditional Finnish sauna with a wooden floor, additional insulation of the floor is not recommended. Why? Wood itself is a material that insulates well and does not conduct cold. A properly constructed and ventilated floor will not be prone to rot and will not feel cold. Additional insulation could interfere with the natural weathering process of the wood, leading to moisture retention and potential damage to the floor. In a traditional Finnish sauna, where the humidity is low and the floor is often made of pine or spruce boards, the natural properties of the wood are sufficient to ensure comfort and durability, without the need for additional insulation.

Won’t the floor be cold if it is not insulated?

In a Finnish sauna, where temperatures can reach up to 90-100°C, and where wooden planks are used as flooring, wood itself is an excellent thermal insulator. A wooden sauna floor conducts heat well, but not so much as to be unpleasant for the feet.

The main principle of the sauna is to distribute heat evenly throughout the room, including the floor. Because the floor is made of wood, it will be warmer than, for example, a concrete or ceramic floor without additional insulation.

In addition, the room is properly heated before the sauna is used, which ensures that the entire structure, including the floor, is properly heated.

In practice, a properly constructed and heated wooden sauna floor will not feel cold, even if it is not additionally insulated.

Flooring in an indoor sauna

If the sauna is part of the interior of the house or adjacent to the bathroom, here are the rules and recommendations for the floor of such a sauna:

  • Ceramic tiles are the ideal choice, available in a variety of shapes, shades and types. They are characterised by high durability and water resistance. It is important to pay attention to the non-slip properties of the tiles.
  • The surface on which the tiles will be laid must be suitably insulated, preferably using XPS insulation.
  • Tiles can be hot, so walking on them may be less comfortable. A solution may be to use a wooden mat on top.

Example of sauna floor structure in a room:

  1. XPS insulation
  2. Concrete floor
  3. Waterproof coating
  4. Flexible adhesive for tiles
  5. Ceramic tiles

This indoor sauna floor configuration combines both visual appeal and practicality. Choosing the right materials and carefully planning the structure is the key to creating a long-lasting and functional floor.

For a sauna located in an interior room, proper drainage is an important aspect. You should think about locating the drain at a strategic point, such as under the cooker, where water naturally collects, especially in a steam sauna. The drain should be integrated with a siphon to prevent unpleasant odours from entering the sewer system, and also protected with a grille for extra safety. Drainage of excess water in this way will make it easier to keep the sauna clean and help maintain proper hygiene.

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Since 2011 I have had my own business selling sauna building materials, sauna cookers and sauna accessories. I know all about building a quality sauna!