Tom Webster asks do we need to rethink what we call ‘best practice’ in a world striving for circularity?

Yesterday we had the privilege of touring 30 Duke Street, a remarkable project delivered by Mace in collaboration with their client GPE. Circular thinking has been embedded throughout; not just in design, but in procurement and delivery too. The achievements in reusing structural steel, façades, windows, and raised access flooring are genuinely impressive (for example, 78% of the frame is from reclaimed steel).

But as we walked the site, I spotted something that made me pause: long-span floor beams, spliced with full penetration butt welds right in the middle third. And suddenly, I heard the voice of my first principal engineer echoing from 20 years ago: “Splices should never be in the middle third of a beam.”

It’s a voice many of us in the profession will recognise, an internal sense of ‘right’ based on rules passed down unquestioned. But experience has taught me to interrogate that voice. These welds were made offsite, in factory-controlled conditions. They’ve been tested. They’re not in key elements. Any failure mode is likely to be ductile and deformation driven. And in truth, the splice is probably stronger than the original section. The rational part of the engineer takes over, and I can climb down from that reflexive anxiety.

Reflecting on the tube back to the office, I realised again how deeply our profession is shaped by received wisdom, much of it rooted in training and codes that were maybe outdated even when we were taught them.

But engineering doesn’t live in a perfect world. Our job is to understand risk, to manage it, and to balance trade-offs in real-world contexts. This is especially true in a circular economy, where the reuse of materials demands us to think beyond tradition. We’re going to face countless moments like this: when the ‘textbook’ solution might go against the sustainable one. In these cases, is it more important that the splice is in the technically ideal position — or to maximise the amount of steel reused and minimise waste? And whilst this is a specific rhetorical question, it will apply to all sorts of problems that we face in a project environment.

I suspect the answer will be ‘it depends’. And that’s why structural engineers are so critical to the circular transition, because we are trained to hold competing risks and make nuanced, informed decisions.

Congratulations to Mace, GPE, and Elliott Wood on delivering a bold and thoughtful project. It’s a real benchmark for how engineering must evolve to meet the challenges and opportunities of a circular future.

Tom Webster is a Board Director at Webb Yates, and a member of The Engineers Reuse Collective’s Steering Group.