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Sauna timber and cladding are specifically selected for performance in high-temperature, low-humidity environments where stability, low resin content, and surface comfort are essential. Unlike standard interior timber, materials used in saunas must withstand repeated heating cycles without excessive movement, resin bleed, or surface degradation.
This category includes timber suitable for sauna walls, ceilings, and seating, covering both tongue and groove cladding profiles and smooth planed boards. Common choices such as Nordic spruce and thermally modified timber are widely used in UK sauna construction due to their consistent appearance, reliability, and balanced cost-to-performance ratio.
Sauna cladding is typically installed using tongue and groove (T&G) boards to create a tight, uniform internal lining. These profiles allow for efficient installation while delivering a clean, continuous finish across walls and ceilings. Light-toned timbers are often preferred for sauna interiors, helping to maintain a bright, natural aesthetic while remaining comfortable to touch under heat.
In addition to cladding, dedicated sauna bench boards are used for seating areas. These are manufactured with smooth finishes and appropriate dimensions to ensure comfort, durability, and safe use in high-temperature conditions. Seating timber is selected differently from cladding, focusing more on tactile quality and heat transfer performance.
All sauna timber should be installed onto a suitable battened substructure with provision for airflow behind the boards. Proper detailing, including expansion allowance and the use of stainless steel fixings, ensures long-term performance and reduces the risk of movement or moisture-related issues within the build-up.
Whether you are building a residential sauna, garden sauna room, or a larger spa installation, selecting the correct timber is key to achieving a durable, functional, and visually consistent result.
For seating applications, view our sauna bench boards, specifically designed for comfort and durability in sauna environments.
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Timber cladding performs best when designed as a ventilated rainscreen system rather than simply fixed directly to a wall. A drained and ventilated cavity helps manage moisture and improves long-term performance in UK weather conditions. Species choice then becomes a balance between dimensional stability, durability class and surface behaviour over time. ThermoWood cladding (Thermo Pine / Thermopine) is selected for enhanced stability and reduced movement. Siberian Larch cladding offers natural durability and strong grain character. Shou Sugi Ban wood (technique), often referred to as charred timber or burnt Japanese wood, provides a surface-stabilised architectural finish with distinct visual depth. Nordic Spruce cladding is a consistent softwood solution commonly specified for coated or treated façade systems. Where reaction-to-fire performance is part of the specification, review fire rated cladding options early, as Euroclass performance depends on the full wall build-up and treatment process. For broader façade detailing and installation context, see The Ultimate Guide to Timber Cladding in the UK.
| Feature | ThermoWood | Siberian Larch | Shou Sugi Ban (Charred Timber) | Nordic Spruce |
|---|---|---|---|---|
| Dimensional stability | High (thermally modified) | Moderate | High (surface-stabilised) | Moderate |
| Typical durability (EN 350) | Class 2–3 | Class 3 | Improved surface durability | Class 4–5 (untreated) |
| Moisture movement | Reduced | Medium | Reduced | Higher than modified timber |
| Fire treatment options | Available | Available | Available | Available |
| Typical applications | Modern façades, battens | Rainscreen, mixed-use builds | Feature elevations, architectural façades | Coated façade systems |
ThermoWood cladding is thermally modified to reduce moisture movement and improve dimensional stability. Siberian Larch cladding relies on its natural durability and dense grain structure. ThermoWood typically offers lower movement risk, while Larch provides a more pronounced natural character.
Shou Sugi Ban wood, also known as charred timber or burnt Japanese wood, forms a carbonised surface layer. Depending on the finish level (brushed, sealed or stained), periodic inspection is recommended. Sealed systems require maintenance similar to other coated cladding systems.
Timber cladding can be supplied with fire-retardant treatment to achieve improved European reaction-to-fire classifications. The final Euroclass rating depends on the species, treatment process and complete wall build-up. Always confirm the required classification with building control before specification.
Service life depends on species, detailing and exposure. Thermally modified timber and naturally durable species such as Siberian Larch typically provide long above-ground service life when installed as a ventilated rainscreen system with correct ground clearance.
Yes. All exterior timber, including ThermoWood, Larch and Nordic Spruce, will gradually weather to a silver-grey tone if left untreated. This colour change does not reduce structural performance and can be managed with UV-protective coatings if colour retention is required.