38 | Sector Focus: Timber Construction
LANDMARK BUILDING PROVES CLT’S MULTIPLE PLUSES
TTJ asked Dr Mila Duncheva, Stora Enso business development manager
for UK and Ireland, and global business project manager, about the use of its engineered wood in the construction of London’s Timber Square
course of months, with those materials exposed to adverse weather conditions such as rain. That can damage the visual quality of the materials and, in extreme cases, their functionality. Therefore, we pre-applied a temporary membrane and end grain sealer to the CLT panels to mitigate the risk.
Above: Dr Mila Duncheva
TTJ: Was the use of engineered wood on the table for Timber Square from the start?
Dr Mila Duncheva: The developer Landsec envisaged this project as one of the first net zero commercial buildings. This meant turning to a material that could cut both operational and embodied emissions, and so mass timber was an option early on.
TTJ: What function does Stora Enso CLT perform in the building? MD: Timber Square is an excellent example of how concrete, steel and timber materials can be combined in a hybrid project. The structure consists of retention of an existing structure concrete core, structural steel frames (beams and columns), and timber CLT slabs to transfer the horizontal load. The CLT provides a fundamental structural role for the floors in supporting people and equipment.
TTJ: What volume of CLT was used and how was it protected during the construction process? MD: The two buildings of Timber Square use approximately 6,500m3
of CLT,
manufactured by us and supplied to Mace by Hybrid Structures. The significant scale of the project is an important consideration when it comes to the materials used because construction took place over the
TTJ: Is transport of the CLT to site accounted for in building carbon footprint calculations? MD: The CLT for Timber Square was manufactured in Sweden, Austria and the Czech Republic. For the Austria and Czech Republic transport routes, the material travels by truck from the mill to Rotterdam, then by ship to Purfleet on the Thames, followed by truck to the Timber Square site. From Sweden, the CLT is transported by truck to Gothenburg port, then ship to Immingham, and truck to site. The trucks stay packed for transit by ship, so there is no need for the CLT to be unloaded and reloaded. That transport is considered and measured using Stora Enso’s carbon calculator. We identified that the transportation of the CLT emitted 200 tonnes of CO2
e and the
manufacturing of the CLT emitted 345 tonnes of CO2
with the 7,500 tonnes of CO2
e. This compares favourably e avoided
by using wood in place of non-renewable construction materials and the 5,000 tonnes of CO2
trees and stored in Timber Square.
TTJ: Advantages cited for building with engineered wood are that it’s a quieter, cleaner, quicker process than masonry construction – were these apparent on Timber Square? MD: Timber Square is close to the Thames and London landmarks such as the Shard and Tate Modern, which means space is precious. The use of CLT has an efficiency advantage in these crowded urban environments because it arrives according to a pre-agreed schedule and can be lifted directly from the truck using a crane, reducing storage time needed in a
e removed from the air by the
TTJ: According to an office building rental business a timber building they commissioned recently rented quicker than its other premises due to its environmental positives. Do you recognise this experience? MD: Mass timber elements have significant benefits that increase a building’s value to tenants and developers. The first is the biophilic nature of wood surfaces that contribute to physical and mental well- being. Forest & Wood Products Australia found the presence of wood correlated with higher satisfaction and lower absenteeism among employees, as well as improved concentration and productivity.
premium location. CLT is additionally fast to install; across Stora Enso projects we see a 30% decrease in construction time compared to traditional methods. CLT is also a highly precise material, cut to a specific size in advance of arrival on site, meaning there is no need for cutting or other adjustments on site. This makes it a lower risk material to handle than concrete, which produces stone dust containing silica that is potentially harmful to workers.
TTJ: CLT is also relatively light, how did that benefit construction and how else were its advantages maximised? MD: Mass timber has a high strength- to-weight ratio, meaning more square metres of the building can be loaded onto fewer trucks. For Stora Enso CLT used in residential building projects there are approximately 80% fewer truck deliveries needed than traditional construction. Ultimately, reaping the largest rewards
from CLT depends on efficient planning and preparation. In the case of Timber Square, the main contractor Mace set the construction programme and brought in sub-contractor Hybrid Structures to optimise structural installation. Additionally, Hybrid Structures worked with Stora Enso to streamline the order of CLT panels on the trucks, which included 3D modelling. That close collaboration is an essential part of keeping these major projects on track.
TTJ | July/August 2025 |
www.ttjonline.com
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