We cannot model for the year 2126

We can model structures to extraordinary precision, calculate carbon and optimise almost every element of a building. But we cannot model for the year 2126. We do not know who will occupy the buildings we are designing today or what society will ask of them.

So perhaps our responsibility is not to predict the future, but to leave the future choices.

London is full of buildings designed for another age that have found new lives. Their original designers could not have anticipated how they would be used today, yet some have accommodated change remarkably well.

Often the reasons are ordinary: robust structures, useful spans, generous floor-to-floor heights, materials that can be understood and repaired and spaces not so precisely optimised for one purpose that another becomes impossible.

Working with existing buildings teaches humility. The building has already survived one set of assumptions about its future. Perhaps we should design new buildings with the same humility, as future existing buildings.

What we design today may still be standing in 100 years

Optimising for today and tomorrow's brief

Efficiency matters. We should use less material, reduce embodied carbon and eliminate waste. But efficiency today and resilience tomorrow are not always the same thing. Remove every apparent redundancy, and we may remove capacity for change. Optimising around today's brief and tomorrow's use may become impossible.

The better question may be not simply how little material we can use, but how much value it can provide over its life.

Retention, adaptability, durability, repairability and disassembly then become part of engineering value. At GPE’s 30 Duke Street St James's, approximately 78% of the steel structure uses reclaimed steel, giving material from one generation of buildings a role in the next.

Engineering becomes not simply an exercise in optimisation, but in stewardship.

This is where Engineering a Better Society begins for us. It is Elliott Wood's purpose, but it is not intended as an answer. It is a challenge to consider what sits beyond the immediate brief.

What should we preserve? Where should we use less? Where might doing slightly more today create greater value tomorrow? Could the existing building do more? Could we create something not simply capable of lasting, but worth keeping?

We will not always know the answer. That is why the questions matter.

The most sustainable building may not be the one with the most impressive performance on the day it opens. It may be the one that, a century later, remains useful and valued enough that somebody chooses to keep it.