We recently took a trip to Finland to get a close, in-depth look at the thermal modification process and the ever-popular Thermo-Nordic Pine.

A winding highway surrounded by dense Finnish forest under cloudy skies, captured during Duffield Timber’s journey.

The journey began at 4am Sunday morning, with a five-hour flight to Helsinki via Amsterdam.

Greeted by the autumnal Finnish air and our host for the trip, we made our way north into the remote pine forests of Mantta-Vilppula.

Did you know? Finland is dominated by Scots pine and Norwegian spruce, which make up roughly 80% of Finland's forest area.

A stand of tall evergreen trees reaching into a bright blue Finnish sky, photographed during Duffield Timber’s visit.

After 260km (161 miles), we pulled up to a traditional log cabin to receive a warm Finnish welcome, some traditional food - including kalakukko, fish baked inside a loaf of bread - and of course a traditional Finnish sauna.

A quiet gravel road curving through a sunlit Finnish forest, captured during Duffield Timber’s visit.

Well-rested after a good night’s sleep, we met with our US-based client, an innovative modular home builder from Los Angeles.

We’ve been working closely with them as they bring their vision to life, which combines pioneering engineering with cutting-edge technology to achieve an impressive build time of just three months.

All present and correct, we made our way to the ThermoWood® thermo-treatment yard to get a close look at the process.

Stacks of neatly piled timber boards outside a Finnish treatment yard, surrounded by pine trees and lakeside scenery during Duffield Timber’s visit.

ThermoWood® pioneered the thermal modification process in the 1990s, as researchers set out to create a natural alternative to chemical treatments for timber.

Developed by the VTT Technical Research Centre of Finland, the process uses heat and steam to transform locally-grown species, such as Scots pine and spruce.

The heat causes hemicellulose - a sugar that decay-causing organisms feed on - to break down. In turn, this improves the wood's resistance to decay. The process also alters the sites that bond with water, improving moisture resistance and stability.

This pioneering technology became the ThermoWood® process, later managed by the International ThermoWood Association.

Stacks of freshly processed timber boards neatly arranged outside a red-roofed building at a Finnish treatment yard, during Duffield Timber’s visit.

During the visit, our hosts shared more about their origin story.

Interestingly, the family business began in beef farming, but with a desire to diversify, they spotted an opportunity to industrialise the thermo-process. Teaming up with a local sauna maker, they designed and built what is believed to be the first thermo-kiln, crafted from a storage container, over 30 years ago.

Since then, they have continued to spearhead the evolution of the industry.

A Finnish timber treatment yard with stacks of timber boards neatly arranged beside red and grey industrial buildings, surrounded by dense forest during Duffield Timber’s visit.

Today, ThermoWood® is exported worldwide and is recognised as the original benchmark in thermal modification, offering sustainable, high-performance timber with a distinctly Nordic heritage.

Stacks of thermally-treated wooden boards neatly piled inside a Finnish sawmill facility, post-thermal process.

As we explored the site, we got a close-up look at their highly developed thermo-chamber (kiln), where the timber is placed ready for the thermo-process.