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CDM designer duties: what contractors need from an engineer

Designer duties under CDM 2015 are not paperwork. Here is what they mean in practice and what a contractor should expect from the structural engineer.

What the duty actually is

A designer must eliminate foreseeable risk where possible, reduce it where not, and provide information about the risks that remain. That applies to the permanent works designer, not only to whoever is appointed principal designer.

Designing out rather than warning about

The hierarchy matters. Changing a detail so a hazardous operation is not required is a discharge of the duty. Noting the hazard on a drawing is not, if the hazard was avoidable. A connection that can be made from a working platform rather than a ladder is better engineering and better compliance at the same time.

Temporary works are part of it

Permanent works designers are expected to consider how the structure will be built, not only how it will stand once finished. A sequence that requires an unstable intermediate condition is a design issue, even though the finished structure is sound.

What contractors should be given

The residual risks that are not obvious to a competent contractor. Assumptions about the construction sequence. Any element whose stability depends on something being installed before something else is removed. Temporary works requirements identified at design stage rather than discovered on site.

What good looks like

Information issued when it is needed rather than after the event, and an engineer reachable when the sequence turns out to differ from the assumption. Ground conditions and existing structures rarely match the survey exactly, and the cost of that is measured in how quickly it gets resolved.

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