How Does Thermally Modified Timber Cladding Work?

Thermal modification heats timber to above 180°C in a low-oxygen environment, which permanently alters the wood's cell structure — reducing its ability to absorb moisture and breaking down the sugars that fungi and insects feed on. The result is a timber that resists rot and dimensional movement far better than the untreated softwood it started as, without any chemical preservative involved.

Thermory's process is applied to species like ash and pine that wouldn't otherwise be considered suitable for exterior cladding in a monsoon climate. The trade-off is a modest reduction in the wood's structural strength, which is why thermally modified timber is used for cladding and decking rather than structural framing.

Left unfinished, thermally modified timber weathers to a silver-grey patina over one to two years of UV exposure — the same process untreated timber goes through, just starting from a more stable base material. Fabrich can supply either the natural finish or a pre-weathered silver-grey colourway for projects that want that look immediately.