“Concrete or steel?” is rarely a technical question. Both will carry the building. The question is which costs less, all in, over the horizon the client actually has in mind — and that is not settled by habit.
Construction cost is only one of four axes
Comparing construction sums alone ignores part of the spend. A useful comparison sets four things side by side: construction cost, programme, operating conditions, and maintenance over the intended service life.
Programme is not a comfort criterion. For a building meant to produce or to let, every month gained has a value that can be quantified, and that value frequently exceeds the cost difference between two structural options.
An option cheaper to build and dearer to run is not a saving. It is a deferral.
What a measurement changes
A rate per square metre is useful for framing an order of magnitude, not for deciding. It ignores span, clear height, ground conditions and access constraints — precisely the parameters that make the two solutions diverge.
A measurement quantifies the actual structure. It surfaces what a rate hides: that a lighter steel frame also lightens the foundations, or that a slightly reduced span tips the balance. It is design work, and it costs a fraction of what it avoids.
What a comparison must contain
- A measurement by trade package for each option, against the same brief
- Prices from the local market at a stated date, not from memory
- The effect on foundations and on earthworks
- An outline programme, with the value of time to the client
- Operation: clear height, grid, flexibility of layout
- Maintenance over the intended life, corrosion protection included
Decide, then hold to it
The point of a techno-economic study is not to produce a document but to make the decision explicit and traceable. Everyone can see what it rests on, and which price and programme assumptions support it.
It is also what allows the decision to be revisited properly if the context changes. A decision taken on figures is revised on figures; a decision taken by habit is not revised, it is endured.
