Dalibor Savovic, Senior Associate at DeSimone, highlights mass timber’s role in sustainable building, retrofitting, and reducing carbon emissions in construction.

The familiar rhythm of development with steel beams and concrete slabs, the heartbeat of modern construction, has begun to feel a bit... predictable.

Look out over any of the world’s major cities and you’ll observe that the physical projection of human ambition has long been expressed in steel and concrete — which, for sure, have been the go-to structural materials to give form to our lofty ambitions and desired urban density. 

In the realm of structural engineering, this material selection has long been driven by factors such as strength and performance, and I've had a hand in designing buildings constructed using these materials in bustling metropolises like Dubai, Mumbai, and, more recently with DeSimone, in London. 

Beneath the veneer of modern engineering, though, a persistent question lingers for us all: How can we balance the impulse to build more, and taller, with the urgent need to confront the environmental challenges of our time?

While concrete and steel will undoubtedly remain pillars of construction, and without sounding like a false preacher (there are obstacles!), the resurgence of a material as ancient as civilisation makes sense.

Mass timber construction is picking up pace as developers consider more sustainable and efficient building materials. It’s no silver bullet, but a hugely important part of the solution when it comes to lowering the embodied carbon footprint of buildings, if it’s harvested responsibly.

Mass timber products are composed of layers of wood joined together to form strong panels or beams. Due to its laminate composition, meaning it’s stronger, stiffer and more consistent than soft or heavy timber, various engineered mass timber products such as cross-laminated timber (CLT), glued laminated timber (GLT), nailed-laminated-timber (NLT), and laminated veneer lumber (LVL) have made constructing larger spaces more viable. As such, timber buildings are becoming taller and more prevalent worldwide, notably in nations such as Denmark, Germany, and Sweden, which culturally embrace the material for construction.

While living in Denmark for a few years, tasked with spearheading the high-rise engineering team for an international consultancy, I saw timber becoming popular in Scandinavian architecture again. Unsurprising, perhaps, for a nation that puts ‘hygge’ living — an atmosphere of comfort, contentment and wellbeing — at the heart of its cultural experience.

While this movement toward mass timber isn’t exclusive to Scandinavia, the region’s played a pioneering role due to its abundant natural resources, wellbeing focus, and strong support from key industry and government stakeholders.

Fast forward to today, and Wood City, which will become the world's largest mass-timber development, is close to breaking ground in Stockholm.

International building codes have adapted to accommodate this trend. While regulations once limited timber buildings to a maximum of six stories, they now permit structures up to 18 stories tall, expanding the possibilities for mass timber construction as evidenced by Mjøstårnet in Norway.

In the UK, with more stringent legislation and changes to Part B of the Building Regulations banning the use of structural timber in the external walls of residential buildings over 18m tall—which has affected confidence (including among insurers) in using timber for residential multi-storey construction—and a shortage of skills around modern methods of construction, we’re not quite there. 

However, the Timber in Construction Roadmap, launched last year, will (touch-wood!) provide a catalyst for collaboration across the built environment supply chain to accelerate our journey.

As a structural material, timber does not require the energy-intensive production processes of steel or concrete. It also stores carbon as it grows, and can be recycled and reused, which is key to a circular economy. 

Due to its inherent properties of being carbon-friendly and lightweight, we’re seeing timber used to retrofit office buildings with additional stories 

Just a stone’s throw from DeSimone’s office in Clerkenwell, London, the refurbishment of 8 Bleeding Heart Yard transformed an historic Victorian warehouse into a modern, eco-friendly office space by adding two CLT floors as part of an £8m overhaul. What happens, then, if we want to go taller? 

While there’s a case for using timber on buildings up to 18 stories, other materials are likely to be better suited, and more economical, at heights above. We need to choose what’s best for any given situation.

One mass timber project that’s left an impression on me is the 18-storey Kaj (Quay)16 in Gothenburg, Sweden, which I helped design at a previous firm and expects to top out in 2027. It’s a personal project highlight because it offers a path forward for optimum efficiency at greater heights: hybrid timber construction.

Part of the holistic sustainability strategy involved reusing concrete for the cores and podium levels, and employing timber for the remaining superstructure – beams, columns, and slabs. If the cores had been made from timber, they’d have been too large because of the lateral load, leading to inefficient use of materials. By retaining more of the existing structure and building less, the design team countered the developer’s original view that the ‘greenest’ solution would be to construct solely out of timber. 

Buildings are a big part of the problem when it comes to climate change, accounting for 39% of the world's energy-related carbon emissions. A big chunk of that, about 28%, is from the energy we use to heat, cool, and power them. And about 11% of what remains comes from the materials used to build them. Understanding the relationship between embodied carbon and operational performance is key to making targeted decisions to reduce emissions across supply chains and design processes. 

Design for Disassembly (DfD) is an inter-linked sustainable design approach that focuses on creating buildings that can be easily deconstructed and reused at the end of their lifespan. 

As a practice, it’s gaining significant traction alongside mass timber construction because it aligns with the broader goal of reducing waste and embracing circularity. For example, it was considered when forming the sustainability strategy on another project I had some involvement with at Novo Nordisk’s Grange Castle office building in Dublin.

When we use timber to build, that carbon is locked away in the material. Ideally, we'd keep it there forever. But, after a building reaches the end of its lifespan, the timber elements offer the potential to be reused for something else, like building a new eco-home. If that's not possible, it could be turned into a sturdy material with a new purpose, such as an OSB board, or even broken down into fiber and made into paper used to jot down calculations by the next generation of problem-solving engineers. This way, the carbon stays out of the atmosphere for as long as possible.

As a structural engineer, I think it’s more important than ever to be mindful of the materials we use to build things. From the very beginning of a project, I collaborate with architects and other designers to adopt the most sustainable option. We’re not just building buildings; we’re building a better future. We want to create spaces that are not only functional but also kind to the environment and the people who use them. 

That’s a shared vision we can all get behind, right?

Want to hear more? Catch Dalibor Savovic at London Build 2024, where he’ll join the session on Sustainable Practices and Green Building Technologies in Skyscraper Design and Construction.