Thermowood Saunas

Thermowood is the same slow-grown Nordic spruce used across our range, heat-treated at around 200°C in a chemical-free process. The heat permanently alters the cell structure of the timber, driving out moisture and the sugars that fungi feed on.

The result is a sauna that holds its shape. Thermowood is significantly more dimensionally stable than untreated timber, so it moves, swells and warps far less through the wet-dry-freeze cycle of a British year. It is naturally more resistant to rot and decay, and it needs less maintenance to keep looking its best.

It also looks different. The treatment gives the timber a deep, even, honey-brown tone throughout, rather than a surface colour that wears away.

Every Thermowood sauna carries the same 5-year structural warranty and free mainland UK delivery as the rest of our range.

Thermowood sauna FAQs

What is Thermowood?

Thermowood is Nordic spruce that has been heat-treated at around 200°C in a chemical-free process. The heat permanently changes the timber's cell structure, driving out moisture and the sugars that fungi feed on.

Is a Thermowood sauna worth it?

For a sauna that stands outside all year, it is a strong choice. Thermowood moves, swells and warps far less than untreated timber through wet, dry and freezing weather, is naturally more resistant to rot and needs less maintenance to keep looking its best.

Does a Thermowood sauna need treating?

It does not need treating to keep your warranty valid, as long as the sauna is maintained in line with the care guidance in the manual. Pro tip: the exterior colour naturally fades over time, so we recommend a UV-protective finish if you want to keep that rich honey-brown tone.

Which saunas come in Thermowood?

Our Tyyni, Usva and Löyly barrel saunas are all available in Thermowood, from one-person to four-person models, with glass wall options on selected sizes.