Why the concept decides the cost

What the sketch design settles

Not details. The sketch design is about:

• how big the building is and what shape, how many storeys,
• how it sits on the plot,
• what the structural system is and how large the spans are,
• where the bracing elements go,
• where the service risers run,
• roughly which build-ups we are working with.

Most of the cost follows from these. Concept design.

Four typical examples

The span

Half a metre less span often means a whole section size smaller — throughout the building.

The position of the bracing

The floor plan determines where the bracing wall segments go. If there is no continuous wall segment in the right direction, the bracing has to be solved more expensively. Designing a shear wall.

The openings

Too many or badly placed openings take away the wall area available for bracing and create lintel problems. Openings and lintels.

The service risers

If the route of the large-diameter pipes is decided early, the service cavity is enough and no lining wall is needed. Service cavity.

Which is why we say it in the first week

If a form can only be built with a disproportionate amount of steel or concrete, we say so at concept — not at detailed design, when changing it would be expensive.

That is the main difference from a general design where the structure is just one of many disciplines brought in.

What we do not fix yet

Connection details, exact section sizes, named products. Those are the job of the detailed design — fixed early, they are fixed on the wrong basis.

The point

The concept is the cheapest stage and the one with most at stake. An hour of structural discussion here is worth more than a week of patching the detailed design.