8 7 2025 | Environmental safety | Fire protection | wood construction
8 7 2025 | Environmental safety | Fire protection | wood construction
Photos: Kivinen Rusanen Architects, Buckland Timber, Nordtreat
The use of ecological mass timber is expected to increase in the construction of demanding industrial and infrastructure projects. This is made possible by Nordtreat’s bio-based NORFLAM® fire protection technology. Excellent examples include Fingrid’s substation in Espoo and Transport for London metro and railway stations in London.
Massive CLT elements and glulam structures are a responsible and efficient means to reduce the climate impact of construction. They combine the advantages of sustainable, fast, and cost-effective prefabricated construction with the visually appealing look of real wood.
There are no longer obstacles to using mass timber in demanding industrial and infrastructure projects: mass timber structures can be reliably protected to meet the commonly required fire classification B-s1, d0. The certified NORFLAM® fire protection solution is suitable for protecting timber surfaces in both industrial processes and on-site applications.
Completed in 2025, the Hepokorpi substation represents a new way of thinking in critical infrastructure construction, using glulam and CLT structures for the first time in a substation in Finland.
“The ecological benefits, ease of installation, and cost-effectiveness of mass timber structures were realized for the first time in an electricity distribution facility. We believe that the use of properly fire-protected CLT and glulam will increase in demanding industrial projects like these.”
Outi Kallio, CEO, Nordtreat
The glulam and CLT structures of the high industrial hall are large-scale. Using timber in the electricity distribution hall was made possible by Nordtreat’s NT DECO fire protection treatment, which achieved both the required B-s1, d0 classification and the desired light translucent tone.
Nordtreat supports wood product manufacturers and surface treatment companies in certifying their fire protection processes. Additionally, painting and surface treatment contractors are trained on-site to ensure and verify compliance when using Nordtreat’s fire protection products.
Due to the scale and complexity of the Hepokorpi project, Nordtreat carried out the fire protection treatment on-site with its experienced specialists Markus Strömberg and Janne Hirvonen.
“Fire protection of large timber surfaces is often easier to complete on-site after the structures have been installed. The most important aspects are scheduling the work according to the construction progress and ensuring the correct treatment conditions.”
Pekka Hurri, VP Services, Nordtreat
The challenges in fire protecting the wooden surfaces of Hepokorpi’s substation included the building’s height, scale, and managing fire protection across two different types of wood surfaces. The correct amount of NORFLAM® W310 (NT Deco) flame retardants needed to be absorbed within the required timeframe to verify the fire classification. Since glulam surfaces are denser than CLT, their absorption and drying rates differ.
“We carried out the fire protection in sections using a personnel lift, treating one area between pillars at a time from top to bottom. We utilized the ceiling seams to ensure even application while maintaining consistent color tones. Achieving the B-s1, d0 classification required four coats on each surface.”
Janne Hirvonen, Surface Treatment Specialist, Nordtreat
Working at a height of 10 meters required caution and precision. The variable weather conditions during the rainy season affected temperature and humidity, impacting the treatment process. The work was planned and documented according to the building layout, ensuring fire protection was verified for each section.
“We completed 150–200 m² of treated surface per day. Janne handled the application with a high-pressure sprayer and lift, while I ensured proper conditions, calculated the required application amounts, and monitored the process.”
Markus Strömberg, Surface Treatment Specialist, Nordtreat
The fire protection work took about four weeks during spring 2024. The light translucent tone of the product allows the wood grain to remain beautifully visible, resulting in a clean, refined finish. After the treatment dried and settled, the surfaces were wiped with a damp microfiber cloth, completing the fire protection treatment.
Explore the Fingrid Hepokorpi Substation Reference
In 2024, Buckland Timber delivered CLT structures for two flat roofs at the Surrey Quays railway station in London. Additionally, Buckland Timber manufactured and installed striking glulam arches and structural beams made of CLT and glulam for the new ticket hall at Colindale Underground Station.
"Nordtreat’s flame retardant solution is perfect for us. Besides providing the required B-s1, d0 reaction to fire performance, the product is waterborne, non-volatile and suitable for the on-site and offsite treatment of our large CLT and glulam structures. I also find the range of translucent colours very useful.”
Jess Pearce, Engineer & Project Manager, Buckland Timber
For London’s transport projects, the certified fire protection treatment of the massive timber structures was carried out at Buckland Timber’s factory.
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