- Lunawood ThermoWood is thermally modified Nordic pine and spruce produced in Finland using only heat and steam — no chemicals, no preservatives.
- It is not the same as generic ThermoWood — Lunawood is a specific brand with its own production process, profile range, and quality standards.
- Lunawood carries a BRE-accredited 30-year service life for external cladding and is classified as Durability Class 2 (BS EN 350).
- Fresh Lunawood has a warm honey-brown colour that weathers naturally to silver-grey — both are popular finishes requiring no ongoing treatment.
- Available in the UK in triple shadow gap, double shadow gap, shadow gap, tongue and groove, and rainscreen profiles — all from stock with delivery in 7–14 days.
Lunawood ThermoWood is one of the most frequently searched timber cladding brands in the UK specification market — and one of the most misunderstood. The term is often used interchangeably with "ThermoWood" as if they mean the same thing. They do not. Lunawood is a specific Finnish manufacturer with its own patented production process, its own profile range, and its own quality standards — all of which set it apart from generic thermally modified timber available from other suppliers. This guide explains exactly what Lunawood ThermoWood is, how it is produced, why architects specify it, and what you need to know before buying it in the UK.
We are a specialist UK supplier of Lunawood ThermoWood, stocking the most popular profiles for immediate delivery across the UK with FSC and PEFC certification. This guide draws on our direct experience supplying Lunawood to architects, contractors, and homeowners across the UK.
What Is Lunawood ThermoWood?
Lunawood ThermoWood close-up — the warm honey-brown colour and resin-free, consistent grain are the result of thermal modification using only heat and steam.
Lunawood ThermoWood is thermally modified Nordic pine (Pinus sylvestris) and spruce (Picea abies) produced by Oy Lunawood Ltd at their production facility in Finland. The timber is heated to 185–215°C in a closed kiln environment using steam, without oxygen and without chemicals or preservatives. This permanently alters the cell structure of the wood — reducing moisture absorption by up to 50%, improving dimensional stability, eliminating resins, and increasing natural resistance to biological decay. Lunawood was a founding member of the International ThermoWood Association and remains one of the world's leading producers of thermally modified timber.
The thermal modification process works by breaking down the hemicellulose in the wood's cell walls — the carbohydrate compounds that absorb moisture and provide a food source for the fungi and bacteria that cause biological decay. Once these compounds are eliminated, the timber becomes significantly less attractive to biological organisms and significantly less reactive to changes in humidity. The result is a timber that behaves more like a hardwood in terms of stability and durability, but retains the workability and weight of the softwood it started as.
Lunawood uses a patented continuous kiln process — rather than the batch kilns used by some competitors — which produces more consistent modification depth and colour uniformity across each timber run. This consistency is one of the reasons Lunawood has become the preferred ThermoWood brand for architects who need to guarantee a specific visual result across large facade areas.
Is Lunawood the Same as ThermoWood?
This is the most common question from UK buyers encountering Lunawood for the first time. The short answer is: Lunawood ThermoWood is a type of ThermoWood, but ThermoWood is not always Lunawood.
ThermoWood is a generic term — and a registered trademark of the International ThermoWood Association — that describes timber which has been thermally modified according to the Association's production standards. Multiple manufacturers produce ThermoWood, including producers in Finland, Sweden, Germany, and other countries. Lunawood is one of these manufacturers — and one of the most technically advanced and quality-consistent in the market.
- Thermally modified using heat and steam
- No chemical preservatives used
- Improved moisture resistance vs untreated timber
- Improved dimensional stability
- Improved natural decay resistance
- Dark honey-brown colour when fresh
- Weathers to silver-grey when untreated
- Patented continuous kiln process — more consistent results
- Founding member of International ThermoWood Association
- BRE-accredited 30-year service life — independently verified
- Specific profile range — triple shadow gap, Luna Aalto, Luna Duo
- PEFC certified from sustainably managed Finnish forests
- CE and UKCA marked — full UK compliance documentation
- Available with Euroclass B-s1,d0 fire rating on request
Lunawood ThermoWood Colour — Fresh, Weathered and Treated
Lunawood ThermoWood weathering to silver-grey — one of the most popular low-maintenance finishes for UK residential and commercial facades.
Colour is one of the most important practical questions for anyone specifying or buying Lunawood ThermoWood. The timber goes through three distinct colour stages over its service life:
Fresh — warm honey-brown
Freshly delivered Lunawood ThermoWood has a warm, uniform honey-brown colour — the result of the caramelisation of natural sugars during the thermal modification process. The colour is consistent from board to board and batch to batch — one of the advantages of Lunawood's continuous kiln process. This is the colour shown in most Lunawood marketing imagery and the colour the timber will have on installation day.
Weathered — silver-grey
When left unfinished on an exterior elevation, Lunawood ThermoWood weathers gradually to a consistent silver-grey patina. The weathering process takes approximately 12–24 months on an exposed south or west-facing UK elevation, and longer on sheltered or north-facing walls. The silver-grey finish is self-consistent — it does not show UV fading or maintenance lapses in the way painted or stained finishes can, and it requires no ongoing treatment whatsoever. This is the most popular finish for Lunawood on UK projects.
Oiled — maintained honey-brown
If you want to maintain the original honey-brown colour rather than allow natural weathering, apply a UV-stable exterior oil within 2–4 weeks of installation before the initial weathering process begins, and re-apply every 3–5 years depending on exposure. Our Koopmans Houtolie and Remmers HK Stain are both compatible with Lunawood ThermoWood and well proven on UK projects.
Lunawood ThermoWood Performance in the UK Climate
Lunawood ThermoWood performing on a UK exterior — the thermal modification process gives the timber Durability Class 2 performance with a BRE-accredited 30-year service life.
The UK climate presents specific challenges for exterior timber — high annual rainfall, frequent wet-dry cycles, persistent low temperatures, and significant UV exposure on south-facing elevations. Here is how Lunawood ThermoWood performs against each of these:
| Challenge | How Lunawood performs | vs Untreated softwood |
|---|---|---|
| Moisture / rainfall | Moisture absorption reduced by up to 50% | High absorption — swells, moves, splits |
| Wet-dry cycling | Excellent dimensional stability — minimal movement | Significant movement — joint gaps open |
| Biological decay | Durability Class 2 — 30-year BRE service life | Class 4–5 — requires chemical treatment |
| UV exposure | Weathers consistently to silver-grey | Uneven greying, surface checking |
| Cold / frost | No issues — stable in sub-zero temperatures | Frost can accelerate surface checking |
| Sauna conditions | ✓ Suitable — resin-free, stable at high heat | Untreated pine unsuitable — resin bleeds |
Where Lunawood ThermoWood Is Used in the UK
Lunawood ThermoWood on a contemporary UK facade — used across residential, commercial, and public building projects for exterior cladding, soffits, and feature elements.
Lunawood ThermoWood is used across a wide range of UK building types and applications. Its combination of stability, durability, and consistent appearance makes it suitable for projects where performance and aesthetics are both critical:
- Exterior facade cladding — the primary application. Shadow gap, triple shadow gap, and rainscreen profiles on residential extensions, new builds, commercial buildings, and public buildings. The triple shadow gap 26x92mm is the most widely specified profile.
- Garden rooms and garden offices — Lunawood ThermoWood is one of the most popular cladding materials for contemporary UK garden office builds, chosen for its low maintenance and consistent appearance.
- Soffits and canopies — the resin-free surface and dimensional stability make it ideal for soffit applications where surface quality and consistency matter.
- Interior feature walls — tongue and groove profiles in ThermoWood pine are increasingly specified for interior wall and ceiling applications in contemporary UK homes and commercial spaces.
- Saunas — Lunawood ThermoWood pine is one of the most widely used materials for sauna interior walls and ceilings. The tongue and groove 19x140mm is the standard interior sauna profile. For more on sauna applications see our ThermoWood sauna profile guide.
- Decking — Lunawood ThermoWood decking boards offer the same stability and durability advantages as the cladding range, in profiles suited to horizontal deck applications.
Lunawood Thermo Pine vs Lunawood Thermo Spruce
Lunawood Thermo Pine — the primary species for exterior shadow gap and tongue and groove profiles, with a tight, even grain that machines to precise profile tolerances.
Lunawood ThermoWood is produced from two Nordic species. Understanding the difference helps you specify the right material for your application:
Lunawood Thermo Pine (Pinus sylvestris)
Nordic pine is the primary species for Lunawood exterior cladding profiles. Its tight, even grain structure machines to precise tolerances — essential for the clean shadow groove edges that define the triple and double shadow gap profiles. Thermo Pine has a warm honey-brown colour with small, round knots and minimal grain variation. It is the species used in all Lunawood shadow gap, tongue and groove, and rainscreen profiles available in the UK. Also the standard choice for sauna interiors — its low thermal conductivity keeps board surfaces comfortable against skin at high temperatures.
Lunawood Thermo Spruce (Picea abies)
Nordic spruce is used for some wider-format boards and interior profiles. Its longer grain sections allow wider board dimensions than pine. Thermo Spruce has a slightly lighter colour and more prominent round knots than pine, giving it a warmer, more characterful appearance suited to projects where a rustic or natural aesthetic is wanted. Both species achieve the same Durability Class 2 rating and BRE-accredited 30-year service life.
For exterior shadow gap cladding, interior tongue and groove, and sauna applications — specify Lunawood Thermo Pine. For wider-format boards, feature walls where knot character is wanted, or interior applications where a more rustic appearance suits the design — consider Thermo Spruce. If in doubt, contact our team and we will advise on availability and lead time for your project. For a full overview of all available Lunawood profiles see our Lunawood ThermoWood cladding UK guide.
Lunawood ThermoWood is thermally modified Nordic pine and spruce produced by the Finnish company Oy Lunawood Ltd using only heat and steam — no chemicals. The process permanently improves the timber's moisture resistance, dimensional stability, and natural decay resistance. It carries a BRE-accredited 30-year service life for external cladding and is classified as Durability Class 2 (BS EN 350). It is one of the most specified thermally modified timber brands by UK architects.
Lunawood ThermoWood is a specific brand of thermally modified timber produced by Oy Lunawood Ltd in Finland. ThermoWood is the generic term for thermally modified timber produced by members of the International ThermoWood Association — of which Lunawood was a founding member. All Lunawood products are ThermoWood, but not all ThermoWood products are Lunawood. The Lunawood brand is associated with specific profile designs, consistent quality standards, and the Finnish production process of Oy Lunawood Ltd.
Fresh Lunawood ThermoWood has a warm, uniform honey-brown colour. When left unfinished externally, it weathers gradually to a consistent silver-grey patina over 12–24 months. The silver-grey finish requires no maintenance. If you prefer to maintain the original honey-brown tone, apply a UV-stable exterior oil every 3–5 years.
No preservative treatment is required. The boards can be left completely unfinished to weather naturally to silver-grey, or finished with a UV-stable exterior oil every 3–5 years to maintain the original honey-brown colour. Lunawood does not require painting, staining, or any chemical preservative at any point in its service life.
Lunawood Thermo Pine has a tight, even grain and is the primary species for exterior cladding profiles including shadow gap and tongue and groove. Lunawood Thermo Spruce has a more open grain with more prominent knots and suits wider-format boards and interior applications where a more rustic appearance is wanted. Both achieve Durability Class 2 and a 30-year BRE-accredited service life.
Lunawood ThermoWood — UK Stock, Nationwide Delivery
We supply Lunawood ThermoWood cladding profiles across the UK — triple shadow gap, double shadow gap, shadow gap, tongue and groove, and rainscreen — all from stock with delivery in 7–14 days. PEFC certified. Fire rated options available. Send us your profile, m², and postcode for a quote.