At Harrogate Flooring, we’re always looking for ways to bring high-quality, practical timber solutions to our customers across Yorkshire and the wider UK. While we’re best known for our reclaimed pine floorboards and engineered oak flooring, we know many homeowners, builders and designers are searching for durable, attractive exterior cladding that performs well in the British climate without relying on heavy chemical treatments.
That’s why we’re delighted to supply Pine Thermowood Cladding – Shadow Gap. This is thermally modified redwood pine cladding, carefully heat-treated for improved stability and durability, then machined with an extended tongue-and-groove profile that creates clean single, double or triple shadow gap lines.
If you’re researching Thermowood cladding, Thermowood pine cladding, shadow gap cladding, thermally modified timber cladding, PEFC certified cladding, Class 2 durability cladding, or chemical-free exterior timber cladding, this detailed guide is for you. We’ll explain what Thermowood actually is, why the shadow gap profile is so popular, the practical benefits, how it compares with untreated softwood and other options, and why this product is well suited to both contemporary and traditional projects.
You can view the full product details, available widths and current pricing here:
Pine Thermowood Cladding – Shadow Gap
What Is Thermowood and How Does It Work?
Thermowood (also written ThermoWood or thermo-wood) is timber that has been thermally modified using heat and steam only – no chemical preservatives are added. The process was developed in Finland and is now widely used across Europe for exterior cladding, decking and other outdoor applications.
In simple terms, the timber is heated to high temperatures (typically in the region of 180–230°C) in a carefully controlled, low-oxygen environment with steam. This permanently changes the cellular structure of the wood. The result is:
- Significantly reduced ability to absorb moisture
- Improved dimensional stability (less swelling, shrinking, cupping and twisting)
- Enhanced resistance to decay and fungal attack
- A richer, darker colour throughout the board
Our product uses 5ths grade redwood pine (Scandinavian/Scots pine) that has been thermally treated to achieve Class 2 durability according to BS EN 350-2. Class 2 is rated as “durable” and is suitable for above-ground exterior use such as cladding. The timber is also PEFC certified, meaning it comes from sustainably managed forests.
Because no chemicals are used in the modification process, Thermowood remains a natural, biodegradable material that can be handled and disposed of like untreated wood at the end of its life.
The Shadow Gap Profile – Clean Lines and Architectural Interest
The profile on this cladding is designed specifically to create a shadow gap effect. An extended tongue-and-groove joint produces a consistent 10mm wide shadow line between boards. Depending on how the boards are arranged and the exact machining, this can deliver single, double or triple shadow gap looks.
Shadow gap cladding has become a firm favourite with architects and homeowners for several reasons:
- It creates crisp, contemporary horizontal or vertical lines
- The recessed joint adds depth and visual interest as light and shadow move across the façade
- It works beautifully on modern new-builds, garden rooms, extensions and commercial projects
- It can also complement more traditional buildings when used thoughtfully
The boards themselves are 18mm thick with face covering widths of 78mm and 124mm. Lengths are typically 2–5 metres (most commonly 2.5–3 metres), though we can discuss specific length requirements if needed. Price is charged per linear metre, with approximate square-metre costs of around £51–£52 depending on the width chosen. A minimum order of 120 linear metres applies.
Key Benefits of Thermowood Pine Shadow Gap Cladding
1. Excellent dimensional stability
Untreated softwood expands and contracts noticeably with changes in humidity. Thermally modified pine absorbs far less moisture, so movement is greatly reduced. This helps boards stay flatter and keeps the shadow gap lines looking clean and consistent over time – something that is especially important with a profile that relies on precise joint spacing.
2. Improved durability without chemicals
Achieving Class 2 durability through heat treatment alone means you get a long service life (often cited around 30 years for exterior cladding when correctly installed and detailed) without the need for traditional preservative impregnation. This is attractive for environmentally conscious projects and for anyone who prefers to avoid chemical treatments.
3. Attractive natural appearance
Fresh from the treatment process, Thermowood pine has a warm, rich brown tone that runs through the board rather than being just a surface colour. Left unfinished, it will gradually weather to an attractive silver-grey, much like other softwoods and hardwoods. If you prefer to retain the original colour for longer, suitable exterior oils, stains or coatings can be applied.
4. Sustainability credentials
PEFC certification provides assurance of responsible forest management. The thermal modification process itself uses only heat and steam, and the finished product remains fully recyclable and biodegradable.
5. Versatility of application
Suitable for both horizontal and vertical installation (always following good cladding practice with a ventilated cavity). Ideal for house façades, garden rooms, studios, commercial elevations, boundary treatments and feature walls.
6. Competitive performance
Thermowood offers a strong balance of cost, appearance, stability and durability compared with many tropical hardwoods or more expensive modified timbers, while still delivering genuine solid wood character.
Thermowood vs Untreated Softwood and Other Cladding Options
Many people start by comparing Thermowood with ordinary kiln-dried pine or spruce. The differences are significant:
- Untreated softwood typically falls into durability Class 4 or 5 and needs regular preservative treatment or frequent recoating to last outdoors.
- Thermowood reaches Class 2 without chemicals and moves far less with seasonal humidity changes.
- The reduced resin content after heat treatment also means less risk of resin bleed through coatings.
Compared with Siberian larch (often Class 3), Thermowood generally offers better dimensional stability. Against more expensive options such as thermally modified hardwoods or certain tropical species, it provides an accessible route to high performance with a distinctive softwood aesthetic (including the natural knots of 5ths grade).
Composite or fibre-cement cladding systems can offer lower maintenance, but many homeowners and designers still prefer the warmth, texture and natural weathering behaviour of real timber. Thermowood sits comfortably in that preference while addressing some of the traditional drawbacks of softwood cladding.
Installation and Detailing Considerations
As with any exterior timber cladding, good design and installation practice are essential for long-term performance:
- Always install over a ventilated rainscreen cavity so the reverse of the boards can dry out.
- Use stainless steel fixings suitable for exterior use.
- Allow for the recommended movement gaps and follow manufacturer guidance on fixing centres.
- Ensure the substructure is sound, level and correctly detailed with appropriate membranes and flashings.
- Consider the orientation (horizontal or vertical) and how water will shed from the façade.
Because the boards have already been thermally modified, they arrive with a low moisture content and good stability, which helps the installation process. We recommend ordering a sensible surplus (discuss this with your cladding installer) to allow for cutting and any future needs. Minimum order is 120 linear metres.
Lead times are typically 1–4 weeks depending on demand. Nationwide pallet delivery is available, and local collection from our Harrogate workshop is also possible.
Finishing Options and Long-Term Appearance
You have two main routes:
- Leave it to weather naturally – The warm brown tone will gradually silver over a period of months to years depending on exposure. Many people love this natural, low-maintenance look.
- Apply a protective coating – Exterior oils, stains or film-forming finishes can help retain more of the original colour and provide additional surface protection. Because the timber is more stable and lower in resin, coatings often perform better and last longer than on untreated softwood.
Regular inspection and maintenance of any coating system (or simple cleaning if left to weather) will keep the cladding looking its best for decades.
Why Choose This Product from Harrogate Flooring?
We supply this Thermowood pine shadow gap cladding alongside our established ranges of reclaimed pine flooring and engineered oak. Customers benefit from:
- Competitive pricing and transparent square-metre cost guidance
- Clear product information and advice on quantities and profiles
- Nationwide delivery or local collection
- A Yorkshire-based team that understands both flooring and exterior timber applications
Whether you are cladding a garden room, updating a house elevation, or specifying material for a larger project, we are happy to discuss requirements and help you calculate the quantities needed.
Ready to Explore Thermowood Shadow Gap Cladding for Your Project?
Thermowood pine shadow gap cladding combines the natural beauty of solid timber with modern thermal modification technology. You get improved stability, Class 2 durability, chemical-free treatment, PEFC certification and a clean contemporary profile that looks excellent on a wide range of buildings.
It is a practical, attractive and responsible choice for anyone who wants real wood cladding that performs reliably in the UK climate.
Browse the full specification, widths and current pricing here:
Pine Thermowood Cladding – Shadow Gap
Order samples if available, ask us about lead times and quantities, or discuss your project with the team. We’re always happy to help.
Get in touch with Harrogate Flooring:
Website: www.harrogateflooring.co.uk
Phone: 07479 235832
Email: sales@harrogateflooring.co.uk
We supply Thermowood cladding, shadow gap cladding, thermally modified pine cladding and other quality timber products to homes and projects throughout Yorkshire (including Harrogate, York and Leeds) and across the UK.
Thank you for reading. We look forward to helping you create a durable, beautiful exterior finish with genuine timber character.
Harrogate Flooring – Specialists in quality timber flooring and cladding, manufactured and supplied from Yorkshire, delivered nationwide.