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ThermoWood cladding is thermally modified timber designed to improve durability, dimensional stability, and long-term exterior performance. We supply Lunawood ThermoWood — produced by Oy Lunawood Ltd in Finland, one of the world's leading thermally modified timber manufacturers and a founding member of the International ThermoWood Association.
Using a controlled heat and steam process (185–215°C) without chemical preservatives, the timber's internal structure is permanently altered. This reduces moisture absorption by up to 50%, limits swelling and shrinkage, and increases resistance to fungal decay — achieving Durability Class 2 (BS EN 350) with a BRE-accredited 30-year service life for external cladding applications.
Lunawood ThermoWood is widely specified across the UK for residential facades, house extensions, garden rooms, garden offices, and commercial buildings. Thermo Pine and Thermo Spruce offer excellent dimensional stability in the UK's wet climate, minimising distortion, surface cracking, and movement when installed as part of a ventilated rainscreen system with stainless steel fixings.
The thermal process gives the timber a rich honey-brown tone which weathers naturally to a consistent silver-grey if left untreated — no preservative treatment required at any stage of its service life. Performance characteristics remain consistent regardless of colour change.
PEFC certified — sustainably sourced from managed Nordic forests. All Lunawood ThermoWood profiles are available with Euroclass B-s1,d0 fire retardant treatment on request, subject to full system specification and building control approval.
We supply Lunawood ThermoWood cladding from UK stock in a range of profiles including triple shadow gap, double shadow gap, shadow gap, shiplap, tongue and groove, and rainscreen — suitable for modern and traditional architectural projects across the UK. Nationwide delivery in 7–14 days.
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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.