What type of wood is best for an outdoor sauna?

What type of wood is best for an outdoor sauna?

There are many wood options available when purchasing a sauna. The type of wood you choose for your sauna will determine by durability, resistance to temperature and weather changes over time, aesthetic, texture and feel on the skin, if’s scent and therefore should be considered a priority when you buying for a sauna. 
There are five types of timber that are most common among our customers. Siberian Spruce, Siberian Cedar, Larch, Thermowood and Pine. All of them are different in colour and texture as well as in wood characteristics. This will help guide you towards the right wood choice for you.

Spruce/Siberian spruce

Spruce grows in whole Europe.
Siberian spruce sauna is the most popular selection. Wood is white, light, and soft, very versatile, easy to work with and maintain. Spruce wood coming from northern growing areas is the most upmarket spruce wood because it has a finer wavy grain. Spruce timber can be stained virtually in any colour you wish to suit your garden landscaping, which is not the case with Thermo wood or Larch. Spruce is one of the sturdiest types of wood, strong, stiff and tough however, it is not naturally resistant to the rot thus it must be regularly treated and sealed, but with the correct maintenance, Siberian spruce is a perfect selection in most climates. It is highly recommended to treat the wood on the outside 1 or 2 times a year, by using impregnation.
With its strength, flexibility, and natural good looks, spruce is a great choice for wood siding. The wood yields tar, pitch, turpentine, rosin, wood vinegar, and tanning substances. The leaves are used to make spruce beer.
Spruce strengths:
It doesn’t conduct heat and it doesn’t leak resin.
It is one of the sturdiest types of wood.
Versatile, easy to work with and treat
Strong, stiff and tough
Readily available
Spruce weaknesses:
Susceptible to rot
Must be regularly treated and sealed

Siberian Cedar (Pinus Sibirica)

The Siberian cedar (more accurately, the Siberian cedar pine, because botanists classify it in the family of pines) possesses enormous hardiness and is found far to the north. The cedar is even found in the Arctic Circle, and grows in the permafrost.

Siberian Cedar improve the quality of the air, give it curative powers. The essential oils contained in cedar needles, which provide it with a refined aroma, possess a bactericidal effect — the air in cedar forests is practically germ-free.

Siberian cedar wood is soft and is easily machined and processed.
Cedar has heartwood of a light yellowish-pink colour, not sharply demarcated from the wide, yellowish-white sapwood, with a barely noticeable transition from early wood to older wood. Siberian Cedar also has significantly less resin ducts than Scots pine, but they are larger.
The properties of the Siberian Cedar permit it to be machined with ease, the losses from drying process are minimum and when dried the weight of Siberian Cedar falls into medium weight category. These in turn permit cost-effective transportation of the Siberian Cedar products to Europe.
Apart from being highly rot-resistant, it is extremely mosquito-repellent. Unlike its many relatives in Pinaceae family as well as its Fake Cedar brothers, it does not cause skin or respiratory problems for people with relevant health issues. Due to its impressive qualities in Russia and in China floors and walls of operation rooms in hospitals are often lined with Siberian Cedar cladding and decking. Its smell, and energetic properties – if you believe in that kind of knowledge – have a healing effect that assists a speedy recovery of a patient.

Timber from the Siberian Cedar is used in many industries, with most common uses being: saunas, outdoor furniture, boat interior and exterior, decking, cladding, housing construction, musical instruments manufacture, very suitable for pencil production, saunas, pillars and profiled beams.

Nevertheless, the strong value of the Siberian cedar are its nuts. Cedar nuts collected in the environs of Leningrad (and, as an analysis has demonstrated, they are in no way inferior to those from Siberia) contain 61% oil, 20% proteins, 12% carbohydrates.

Key Qualities
Resistance to Decay: Siberian Cedar is graded just as high as the Siberian Larch, and is classified as very resistant.
Longevity: Anything made out of Siberian Cedar has a longevity of service.
Strong and pleasant odour: high natural insects repellent properties.

Larch / Siberian Larch

Larch trees grow throughout Europe and belong to the less deciduous conifer trees.
Larch wood is frequently used for outdoor purposes due to its hardness. It is also used in the ship- and boat crafting area. It is very decorative and reaches a very high hardness level. Larch is a wood valued for its tough, waterproof and durable qualities. Larch is a highly ecological, people-friendly and warm building material. Larch is much more resistant to insects and decay compared to spruce.
Siberian larch becomes more and more requested due to environmental aspects. Because of its density and richness of the tar and resin Siberian larch is very durable material for outdoor use, even without additional finishing. Siberian Larch is a strong and dense timber. Thanks to its high gum content, Larch can be used in its natural form. The gum is distributed very evenly between the fibres of the wood, which has an antiseptic effect, protecting it against moisture and insects. Over time its resilience and density will only grow. The timber is naturally very durable and requires no harmful chemicals to preserve it. Larch is a perfect alternative to impregnated wood for outdoor use.

Colour/Appearance: Heartwood ranges from yellow to a medium reddish brown. Narrow sapwood is nearly white and is clearly demarcated from the heartwood. Flatsawn sections can exhibit a lot of character and interesting patterns in the growth rings. Knots are common but are usually small.

Grain/Texture: Grain is generally straight or spiralled. Texture is medium to fine with a greasy or oily feel.

Rot Resistance:  larch is much more resistant to insects and decay compared to spruce.

Sustainability: This wood species is not listed in the CITES Appendices, and is reported by the IUCN as being a species of least concern.

Common Uses: for outdoor purposes due to its hardness. It is also used in the ship- and boat crafting area. It is very decorative and reaches a very high hardness level. The natural resistance to the weather distinguishes larch wood from all other domestic conifer woods.


Thermo-wood is wood having been modified concerning its qualities by means of thermical processing (high-temperature processing). The qualities desired are set by high temperatures (170 up to 230 °C) without the application of any excipients. The process of kilning the timber is environmentally friendly. Since no chemicals are added during the process, it contains only renewable substances.

Thermo-processed wood is darker than natural wood and more weatherproof. Its insulation qualities are better, it suffers from less moisture deformation and is more stable. The equilibrium moisture is up to 50% less than natural wood, which makes thermo-processed wood a better option for use in outdoor conditions.

Thermo process serves for making timber resistant against rottenness. This opens the possibility to also use domestic wood for outdoor purposes. This process avoids that fungal infestation damages appear on the timber after a short time. The timber does not store water so easily and the typical consequences such as bulging, breaking or rottenness are reduced substantially.

Thermowood is known for:

More resistant against rottenness and mouldiness

The timber is getting darker and these dark shades are not UV-resistant

It is an environmentally friendly choice

It is ecological – no chemicals are used

Maintains attractive appearance

Ensures biological durability and dimensional stability

Ideally suited for challenging environments and changing climate conditions


The pine tree occurs naturally throughout northern, central and eastern Europe. The native woodland pine or common pine (Pinus sylvestris L.) belongs to the botanical family Pinaceae, of which more than 100 different kinds can be found in the northern Hemisphere. The most commonly planted variant comes from south eastern Europe, the black pine (Pinus nigra Arnold).

The heartwood and sapwood are easy to distinguish from one another. The sapwood is yellowish-white to reddish-white, the heartwood is reddish-yellow and darkens to a reddish-brown colour. The annual growth ring breadth can vary from between 1 to 10 mm. The reddish summerwood is much darker than the light springwood, the annual growth rings are clearly visible. Depending upon the direction of cut the wood has a striped (radial cut) or wavy grain (cross cut) patterning.

Pine wood is medium-weight and relatively soft. Its strength and elasticity are good. As with other coniferous woods, the properties of the wood depend upon the density of the annual growth rings: The higher the proportion of summerwood, the heavier and harder the wood.

The heartwood has good natural durability except where it is in direct contact with earth or moisture. It has a high natural moisture content, which can lead to a blue staining of the wood through fungal infection. The colouring only affects the appearance, not the physical properties of the wood.


Pine wood can be worked easily by hand or machine. It can be sliced or peeled. Nailed, screwed or glued connections are straightforward. The surface can be finished with all kinds of paints. The sapwood lends itself well to impregnation, less so the heartwood.


Building and construction

Interior furnishing, furniture

Manufacture of composite wood materials

Wood and paper pulp

Masts and poles

Windows, facade panelling

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