Modern architectural exterior design has seen a massive surge in the demand for thermally modified timbers. Among the frontrunners is Thermo Ayous — a timber widely celebrated by architects, designers, and homeowners for modern garden rooms, residential extensions, and commercial facades. But what exactly is Thermo Ayous, how is it made, and why has it become the premier alternative to Western Red Cedar and Siberian Larch?
What is Thermo Ayous?
Ayous (Triplochiton scleroxylon) is a tropical hardwood native to West Africa. In its raw form, Ayous is a light-coloured, fast-growing timber with a clean, clear grain virtually free of knots. However, raw Ayous is not naturally rot-resistant for outdoor UK weather.
To turn it into an exceptional exterior cladding, the timber undergoes a specialized thermal modification process (heating the wood in an oxygen-free chamber to temperatures exceeding 180°C to 215°C with steam). This chemical-free heat treatment permanently alters the cellular structure of the wood:
- Nutrient Removal: It burns off hemicellulose and wood sugars, leaving nothing for fungal spores, rot, or insects to feed on.
- Extreme Dimensional Stability: The timber’s equilibrium moisture content drops dramatically, reducing swelling, shrinking, and warping by up to 80%.
- Rich Exotic Hue: The heat naturally caramelizes the timber, turning the boards an exquisite, warm golden-brown resembling exotic teak or walnut.
Key Advantages of Thermo Ayous Cladding
Thermo Ayous has quickly established itself as one of the best cladding materials on the UK market due to several outstanding properties:
- Durability Class 1–2: Thermal modification elevates Ayous to European Durability Class 1–2 (the highest possible durability rating), giving it an expected service life of 25 to 30+ years above ground.
- Clear, Knot-Free Appearance: Unlike cedar or larch which frequently feature knots or dark streaks, Thermo Ayous offers a remarkably smooth, knotless architectural face.
- Lightweight & Easy to Install: Because moisture and resin are eliminated, boards are feather-light, significantly reducing load weight on building frames and easing installation.
- 100% Sustainable & Non-Toxic: The modification process uses only heat and steam — zero toxic chemicals, biocides, or heavy metals.
Why Choose the Shadow Gap Profile?
One of the most popular profiles for Thermo Ayous is the Shadow Gap profile. When installed either horizontally or vertically, the shadow gap creates a sharp, deep recess line between boards. This architectural feature creates bold linear shadow lines across the facade, concealing fixings and giving garden studios and contemporary homes a clean, seamless finish.
Maintenance: Should You Treat Thermo Ayous?
Thermo Ayous does not require chemical treatment to prevent rot. However, like all natural timbers, exposure to UV radiation will gradually weather the boards to an elegant, silvery-grey patina over 12 to 18 months.
- To Keep the Silvered Look: Leave the timber untreated. It will weather naturally while retaining full rot resistance.
- To Preserve the Warm Teak Colour: Apply a high-quality UV-inhibiting exterior wood oil (such as Osmo or Tikkurila) upon installation and re-coat every 2–3 years.
Buy Thermo Ayous Cladding in the UK
At Ctimber, we stock premium 20 x 144mm Thermo Ayous Shadow Gap Cladding (Sold Per Metre) and Thermo Ayous Tongue & Groove (TGV). Need to calculate board quantities? Use our free online cladding calculator or contact our Surrey sales team for custom cutting and delivery.