Design Responsibility: Descriptive and Prescriptive specifications

When working for Architects as Design Managers, we are often asked about design responsibility – particularly in respect of architectural specifications and the level of detail at tender. The difference between Descriptive and Prescriptive specifications is often an area of confusion for designers and the distinction needs to be made early as early as possible because it impacts all the deliverables, not just the specification.

A descriptive element will represent the design intent, but the final execution of that design, and the responsibility that goes with it lies with the Contractor. But what does that mean for the drawn information? Regardless of the stage the design is passed over to the Contractor to complete, the design will need be coordinated with the other design disciplines; the design intent will need to work. The design information will include detailed GAs, elevations, sections and a specification. Within these outputs the typical conditions should be captured.

A prescriptive element is one where the designer knows exactly what they want and how to achieve it and the specification reflects that with precise references to industry products and the designers certifies that the chosen solution works. The corresponding drawings will reflect this in that the designer will have to draw each unique condition as well.

In a post novation position, we recommend that the split in roles between the novated Architect and the Contractors specialist sub-contractor is clarified early at pre-novation. Traditionally, the Plan A Consultants role ceases at tender but we are increasingly being employed by Architects and Designers to guide them through this post-novation phase.

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