Life: the bit in-between

An internally-located concrete frame that is specified to last for 50 years can last for 100 or more – it’s buy-one get-one-free

The circular economy has been occupying my mind a lot recently – there seems to be a real appetite for more information on exactly how this can be achieved. There’s necessarily been a lot of focus on decarbonisation, but that’s not the end of the story: we will still need to think about how we can design buildings better to meet the challenges of the future.

A core principle of the circular economy is longevity – keeping materials in use for longer – and this is an area where concrete can make an important contribution. In this issue of CQ, we feature an underground station, a school and a house – none of these are fly-by-night structures, and we want them to be useful for decades, ideally for many generations.

We can reduce the embodied carbon of a concrete frame with material-efficient design and low-carbon mix specification. But once it’s built, it becomes a lowcarbon resource for the future. Designed well at the start, a concrete frame can be stripped back, retained and reused many times, as the more temporary layers are replaced and upgraded. In fact, from a structural engineering point of view, a new internally located concrete frame that is specified to last for 50 years can last for 100 or more – it’s buy-one-get-one-free.

That’s not the end of the story. From an architectural point of view, we also need to think about how to make that frame adaptable over time, not to mention beautiful so that people actually want to use them. There can be potential conflicts to resolve – for example, longer 9m spans offer greater flexibility for space planning compared with a more material-efficient 6m span – but, as with everything, it comes down to making reasonable assumptions and working out the optimum balance. We don’t need to design a building to become absolutely anything, we just need to think about what the most likely uses are and build in some capacity
for those alternative futures. Here, the lessons that project teams are currently learning on reuse projects (such as 160 Old Street) will be very valuable.

Embodied carbon is often described in language relating to the birth of a building, and the circular economy is often spoken about in terms of designing for end of life. But I think we’re missing a vital piece of the story: we need to look at what happens in between, the life and health of a building or structure, so that it can continue to serve us for as long as possible. Concrete requires little maintenance over its lifetime, by comparison with other materials, and where required digital technology and AI is helping with diagnosis.

Keeping the buildings we have as healthy as possible for as long as possible is surely the most sustainable solution for all of us – not just in terms of carbon but for the stability of the cities and societies we’re building now.

Elaine Toogood, head of architecture, The Concrete Centre