Looking for exterior cladding that delivers a smooth, contemporary appearance, excellent dimensional stability and strong durability without chemical preservatives? Ayous Thermowood Shadow Gap cladding is increasingly popular for exactly those reasons. This thermally modified African hardwood offers a clear-grade, largely knot-free surface, a warm medium-brown tone after treatment, and performance characteristics that make it well suited to modern façades, garden rooms, extensions and commercial projects.
You can view full product details, available widths and current pricing here:
Ayous Thermowood Cladding – Shadow Gap
What Is Ayous and Why Is It Thermally Modified?
Ayous (also known as Obeche, African whitewood or Triplochiton scleroxylon) is a lightweight hardwood native to the forests of Central and West Africa. In its untreated form it is relatively soft and has limited natural durability for exterior use. Thermal modification changes that.
The Thermowood process uses carefully controlled heat and steam only — no chemical additives. The timber is heated to high temperatures in a low-oxygen environment, permanently altering its cellular structure. The result is:
- Greatly reduced moisture absorption
- Improved dimensional stability (less swelling, shrinking, cupping or twisting)
- Enhanced resistance to decay and fungal attack
- A richer, more uniform mid-brown colour
According to the product information, this process gives Ayous durability comparable to higher-performing species and achieves Class 2 durability under BS EN 350 (with some sources noting Class 1 performance in certain tests). Density is approximately 400 kg/m³, making it one of the lighter hardwood cladding options available — easy to handle and fix while still delivering solid-wood character.
Clear Grade for a Clean Modern Aesthetic
One of the standout features of this Ayous Thermowood is the Clear 4 Sides grade. Boards are largely free of knots, with soft, even grain patterns. This produces a smooth, consistent appearance that many architects and homeowners prefer for contemporary designs. Unlike more characterful species that show frequent knots or strong colour variation, Ayous Thermowood delivers a refined, uniform look that pairs particularly well with glass, render, metal and minimalist detailing.
After thermal modification the timber takes on a warm medium-brown tone. Left untreated and exposed to the weather it will gradually weather to an even silver-grey, much like Western Red Cedar. If you prefer to retain the original colour for longer, exterior oils, stains or suitable coatings can be applied — the timber accepts finishes well.
The Shadow Gap Profile
These boards are machined with an extended tongue-and-groove profile that creates a consistent 10mm wide shadow gap. This allows single, double or triple shadow-gap effects depending on installation and design preference.
Shadow gap cladding is popular because it:
- Creates crisp architectural lines and visual depth as light moves across the façade
- Works equally well horizontally or vertically
- Accommodates minor movement while keeping the joint lines tidy
- Suits both residential and commercial projects seeking a clean, modern finish
Board thickness is 18mm, with face covering widths of 78mm and 124mm. Lengths are typically 2–5 metres (most commonly 2.5–3 metres). Price is charged per linear metre, equating to approximately £81–£83 per square metre depending on width. A minimum order of 120 linear metres applies.
Key Performance Benefits
Dimensional stability
Thermal modification dramatically reduces the timber’s ability to take up and release moisture. This means far less seasonal movement than untreated softwoods or many unmodified hardwoods — an important advantage for maintaining clean shadow-gap lines over time.
Durability
Class 2 durability (BS EN 350) makes the product suitable for above-ground exterior cladding when correctly detailed. Expected service life is typically cited in the 25–30+ year range out of ground contact, provided installation follows good rainscreen practice.
Lightweight and easy to work
At around 400 kg/m³, Ayous Thermowood is noticeably lighter than many traditional hardwoods. This makes handling, cutting and fixing more straightforward on site.
Chemical-free modification
The heat-and-steam process contains no toxic preservatives. The finished product remains a natural, biodegradable material.
Clean, contemporary appearance
The clear grade and even grain give a sophisticated look that many clients prefer for modern architecture, while still offering the warmth and texture of real timber.
How Ayous Thermowood Compares
Versus untreated softwoods
Ordinary pine or spruce generally need preservative treatment and more frequent maintenance for exterior use. Thermally modified Ayous starts with far better inherent stability and durability.
Versus Western Red Cedar
Cedar is a classic choice with beautiful natural colour variation and proven longevity. Ayous Thermowood offers a cleaner, more uniform appearance with fewer knots, excellent stability, and a comparable warm brown tone after modification. It is often selected where a more minimalist, knot-free aesthetic is required.
Versus Thermowood pine
Thermowood pine is an excellent, more affordable softwood option. Ayous provides a hardwood base with a finer, clearer grain and a slightly different visual character that many designers favour for high-end contemporary work.
Installation Considerations
As with any exterior timber cladding, correct detailing is essential:
- Always install over a ventilated rainscreen cavity so the reverse of the boards can dry after rain.
- Use stainless steel or other corrosion-resistant fixings suitable for exterior use.
- Follow recommended fixing centres and allow appropriate movement gaps.
- Ensure the supporting structure, membranes and flashings are properly designed.
- Boards can be fixed horizontally or vertically according to the project design.
Because the timber is already thermally modified and relatively light, it is pleasant to work with. Discuss surplus quantities with your cladding installer to allow for cutting waste and any future needs. Lead times are typically 1–4 weeks. Nationwide pallet delivery is available, and collection from the Harrogate workshop is also possible.
Finishing Options
You have two main routes:
- Leave to weather naturally – The medium-brown colour will gradually silver to a soft grey, creating a low-maintenance, weathered appearance.
- Apply a protective coating – Exterior oils or stains help retain more of the original colour and add surface protection. Re-application intervals depend on exposure and the product chosen.
Either approach can look excellent; the choice depends on the desired long-term aesthetic and maintenance preference.
Why Consider This Product?
Ayous Thermowood Shadow Gap cladding sits in an attractive middle ground: the refined, clear-grade appearance of a hardwood, the enhanced stability and durability of thermal modification, chemical-free processing, and a clean shadow-gap profile that suits contemporary design. It is lightweight, easy to work, and offers strong performance for exterior applications when correctly installed.
For projects that call for a smooth, modern timber façade without heavy chemical treatments or pronounced knotting, it is a compelling option.
Browse the full specification, widths and current pricing here:
Ayous Thermowood Cladding – Shadow Gap
If you would like advice on quantities, lead times, samples or any aspect of your project, get in touch. The team is happy to help.
Contact details:
Website: www.harrogateflooring.co.uk
Phone: 07479 235832
Email: sales@harrogateflooring.co.uk
We supply Ayous Thermowood cladding, other Thermowood options, Western Red Cedar and a full range of quality timber flooring and cladding products to homes and projects throughout Yorkshire and across the UK.
Thank you for reading. We look forward to helping you create a durable, elegant exterior finish with this versatile thermally modified hardwood.
Harrogate Flooring – Specialists in quality timber flooring and cladding, manufactured and supplied from Yorkshire, delivered nationwide.