How quickly can we make the shift to building timber cities?

Posted by Derek Mason

17th January 2023

Picture credit: Annie Spratt on Unsplash

Switching from steel and concrete to timber-based construction isn’t happening on a large scale yet, but it could be one of the solutions to preventing catastrophic climate change.

As cities continue to grow, timber could help us avoid more than 100 billion tonnes of carbon dioxide being released over the next 80 years, according to scientists at the Potsdam Institute for Climate Research in Germany.

Their research, published in the journal Nature Communications, demonstrates how switching from steel and concrete to timber would dramatically reduce the construction industry’s impact on climate change.

The research team used computer simulations to check that it would be possible to make the switch using available timber. They were able to work out that the additional 140 million hectares of forest that would be needed could be established on existing harvested forest areas. This means that agricultural land would not need to be sacrificed.

However, they did also suggest that reducing meat consumption would make it easier to free up enough land for new timber plantations.

This is the first study of its kind – analysing the impact of transitioning to timber cities both in terms of land use, emissions and carbon storage in the timber buildings. Wood has the lowest carbon footprint compared with similar building materials. Trees take up CO2 from the atmosphere as they grow, so timber buildings will be “carbon sinks”.

It all sounds very positive, but it will require a dramatic shift in the way we build. It would mean that whenever we’re building something up to 12 stories high, we need to consider timber as a serious option.

Of course, we’re not talking about raw timber. For the strength needed in construction, we’re looking at engineered wood – products such as cross laminated timber and engineered wooden joists.

One of the challenges is that timber connections are bulky, and you often need steelwork to tie it all together. Better glues are being developed as I write, but at the moment lots of steel bolts and steel plates are being used in timber construction. Another issue is that timber beams need to be larger than steel ones, so floor heights must be higher to accommodate that.

I do think timber construction will be used more and more, but initially we’ll see a steel external frame with timber used internally, rather than full timber buildings. We’ll also need more engineers to be trained in timber design and construction, or the lack of expertise will restrict its use.

And, of course, just because you can run a computer simulation of how to get the volume of timber you’d need, it doesn’t mean that timber will be planted. We’d need to commit to planting enough trees now so that in three to five years’ time we have the timber required to make this shift in our cities. And these plantations will need to be widespread, because if you’re transporting materials over long distances in vehicles run on fossil fuels, the carbon efficiencies are lost.

Constructing homes and other buildings from timber could play a huge part in reducing the impact of climate change, but it looks likely to be a long road to get there in the UK.

Meanwhile, if you need assistance with the structural elements of an upcoming project – timber, steel and concrete or otherwise – please do get in touch.

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