What Is Thermo Aspen?

Thermo Aspen is a thermally modified timber produced by heating sustainably sourced Aspen at extremely high temperatures, almost burnt, without the use of chemicals. This thermal modification process permanently alters the structure of the timber, reducing moisture content and improving stability.

The result is a premium sauna timber that performs exceptionally well in environments exposed to repeated cycles of heat and humidity. Compared with standard timber, Thermo Aspen offers improved dimensional stability, reduced movement and greater durability, making it an ideal material for sauna cladding and sauna bench construction. Its smooth texture, low resin content and attractive golden-brown colouring have made Thermo Aspen a favourite among sauna manufacturers throughout Scandinavia and Europe.

Thermo Aspen offers all of the benefits of Aspen with improved durability and a rich brown finish created during the thermal modification process, while natural (untreated) Aspen remains lighter in colour

Why Thermo Aspen Is Different from Standard Timber

Traditional timber can expand, contract and distort when exposed to the extreme conditions found inside a sauna. Thermally modified Aspen is specifically engineered to minimise these issues. The thermal modification process significantly reduces the timber’s ability to absorb moisture, helping Thermo Aspen sauna cladding remain stable over time. The timber is also virtually resin-free, eliminating the risk of sticky resin bleeding during use. For sauna users, this means a more comfortable experience, longer-lasting sauna interiors and reduced maintenance requirements compared with many standard timber products.

Why Choose Thermo Aspen for Saunas?

One of Thermo Aspen’s biggest advantages is its low thermal conductivity. Put simply, it stays comfortable to touch, even when the sauna reaches high temperatures. Unlike many traditional hardwoods, Thermo Aspen doesn’t become uncomfortably hot, making it ideal for wall cladding, benches and backrests where users come into direct contact with the timber.

This is also due to the timber being thermally modified, which means the timber has been heat treated to improve its performance. This process significantly reduces the natural sap, oils and resins found in untreated timber. In comparison, many traditional hardwoods and softwoods can become extremely hot during use, while untreated timber may release tannins, sap or resin as temperatures rise. Thermo Aspen avoids these issues, creating a cleaner, more comfortable sauna environment.

Thermo Aspen Profiles Available from Southgate Timber

Southgate Timber stocks a specialist range of Thermo Aspen sauna cladding and bench slats suitable for a wide variety of sauna projects.

The current range includes:

• Thermo Aspen 15 x 90mm Channel Groove Cladding STS4
• Thermo Aspen 15 x 120mm Channel Groove Cladding STS4
• Thermo Aspen 28 x 90mm PAR + Rounds Bench Slat
• Thermo Aspen 28 x 120mm PAR + Rounds Bench Slat

These profiles allow customers to create complete sauna interiors using matching Thermo Aspen wall cladding and sauna bench timber. The Channel Groove Cladding profiles can be installed vertically or horizontally, while the PAR + Rounds Bench Slats provide smooth, comfortable seating surfaces specifically designed for sauna use. Manufactured from FSC-certified timber, every profile in the Thermo Aspen range offers the stability, durability and appearance required for premium sauna construction.

Thermo Aspen Sauna Cladding

The Thermo Aspen Channel Groove Cladding profiles are designed specifically for sauna wall cladding and sauna ceiling installations. Available in both 15 x 90mm and 15 x 120mm sizes, these profiles create a clean, contemporary finish suitable for both traditional and modern sauna designs. As thermally modified timber, they remain highly stable despite repeated exposure to heat and humidity. For customers looking for premium sauna cladding in the UK, Thermo Aspen provides an attractive and long-lasting solution.

Thermo Aspen Bench Slats

Comfort is one of the most important factors when designing a sauna, which is why Thermo Aspen bench slats are so widely specified. Southgate Timber stocks both 28 x 90mm and 28 x 120mm PAR + Rounds Bench Slats, providing customers with premium sauna bench timber suitable for seating, backrests and bespoke sauna furniture. The rounded edges improve comfort, while the low resin content and thermal modification process help ensure excellent long-term performance in demanding sauna environments.

Sustainability Credentials

All Thermo Aspen sauna cladding and bench slats stocked by Southgate Timber are FSC-certified, supporting responsible forest management and sustainable sourcing practices. The thermal modification process itself relies solely on heat and steam rather than chemical preservatives, making thermally modified Aspen a more environmentally conscious choice for sauna construction.

Thermo Aspen Maintenance Requirements

One of the benefits of Thermo Aspen is how little maintenance it requires inside a sauna. Unlike exterior timber, it doesn’t require regular coating or treatment. Simply wipe benches and cladding with a damp cloth when required and allow the sauna to air out after each use. Good ventilation between sessions helps keep the timber dry and the sauna fresh, ensuring it continues to perform for many years.

Is Thermo Aspen Right for Your Sauna Project?

Whether you’re building a compact garden sauna, a luxury home spa or a commercial wellness facility, Thermo Aspen offers an excellent combination of appearance, comfort and performance. Its smooth texture, attractive grain, low resin content and exceptional stability have made Thermo Aspen one of the most trusted materials for sauna wall cladding and sauna bench construction. For customers looking for premium sauna timber in the UK, Thermo Aspen represents one of the best options currently available.

Explore Southgate Timber’s Thermo Aspen Range

Southgate Timber now stocks a specialist range of Thermo Aspen sauna cladding and bench slats designed specifically for sauna construction. If you would like advice on choosing the right sauna wall cladding or sauna bench timber for your project, our team is always happy to help. Browse the full Thermo Aspen range online or contact Southgate Timber for expert guidance on your next sauna build.

FAQs

Can Thermo Aspen be installed vertically or horizontally?

Yes. Thermo Aspen Channel Groove Cladding can be installed either vertically or horizontally, allowing flexibility when designing a sauna interior.

Does Thermo Aspen contain knots?

Thermo Aspen contains very few knots compared to many traditional timber species, helping create a cleaner and more consistent appearance throughout the sauna.

What colour is Thermo Aspen?

Thermo Aspen has an attractive golden-brown appearance created during the thermal modification process. Over time, the colour may naturally mellow slightly depending on use and exposure.

Is Thermo Aspen suitable for commercial sauna projects?

Yes. Thermo Aspen is suitable for both residential and commercial sauna installations, including home saunas, wellness rooms, spas and leisure facilities.