Design stages
Why there is more than one design
Section titled “Why there is more than one design”Because design answers different questions, at different times, and different people use it.
Expect a single document and two things go wrong: either details have to be decided too early, before they can be, or it emerges too late that an early decision was wrong.
The stages
Section titled “The stages”Concept design
Section titled “Concept design”The stage of decisions: how big, where, in what arrangement, in what structure. Change is cheapest here, and most of the cost of the project is decided here. Concept design.
Permit design
Section titled “Permit design”Produced for the authority procedure, with the content set by legislation. It is not for building from: it presents the siting, the dimensions, the use and compliance with the regulations. The content of the permit design.
Detailed design
Section titled “Detailed design”Produced for building from, with the content required by government decree 191/2009. It contains the structural design, the connections, the build-ups, the services drawings and the quantities. The content of the detailed design.
Shop drawings
Section titled “Shop drawings”Detailed drawings produced from the detailed design for the manufacturer, matching the equipment and technology of the factory and containing the further information needed for production. Shop drawings.
What happens between the stages
Section titled “What happens between the stages”The stages are not copies of one another. Information is created at every transition:
- from concept to permit design: demonstrating compliance with the regulations,
- from permit to detailed design: the structural design, coordination between disciplines, the connections,
- from detailed design to shop drawings: the requirements of the manufacturing technology and machine processing.
An important rule: the content of the construction documentation may not depart from what the final and enforceable permit contains, and the designer is responsible for observing that.
The typical mistake
Section titled “The typical mistake”Skipping the detailed design and building from the permit drawings. In practice that means the decisions are made on site, by the contractor — generally to suit their own convenience and the material available, not the designer’s logic.
On a light gauge steel or steelwork project this is especially expensive, because manufacture happens in advance: a bad decision cannot be corrected with a chisel on site.
The point
Section titled “The point”Every stage answers a different question. Skipping stages does not save time; it moves the decision to where it will be made worst.