When a design checker is needed

When it is mandatory

Legislation prescribes it within a defined range, generally tied to the significance of the structure or the works. That range changes from time to time, so we check the text in force on a specific project. The design checker.

When we ask for one ourselves

For a bespoke structure

Where there is no catalogue and every calculation is bespoke — a thin-walled steel frame, for example — a second pair of eyes is worth a lot. Not because the designer makes mistakes, but because assumptions slip easily in a complex model.

Where several designers work

Contradictions arising at the boundaries between disciplines can often only be spotted from outside.

Where the structure repeats in quantity

In a structure built in series, one mistake is multiplied. Here the cost of the review is a fraction of the risk.

What a good design check looks at

• the relationship between model and reality: the actions taken, the restraint conditions, the modelling of the bracing,
• the load path: whether the load can be traced from roof to foundation,
• the connections — most mistakes are here, not in sizing the members,
• contradictions between the disciplines’ drawings,
• the completeness of the documentation.

Timing

It works when it happens before manufacture. A fault found at the drawing board is a few hours; the same fault after manufacture means members made, erection and time.

This is not the same as plan review

Design checking is a role defined in legislation and tied to a qualification. Plan review is our service: a professional opinion, with no formal constraints. This is not a design check.

The point

A design check is not mistrust but risk management. Where a bespoke structure is being built, an independent review is the cheapest insurance.