The damning figure in a Royal Institute of British Architects report highlights how unhappy contractors are with designers.
Contractors attacked architects for a lack of “commercial understanding.”
And the report warned: “The larger the project contract value, the more dissatisfied clients are.”
One contractor complained of “too complex design and detailing, despite trying to get the architects to understand our commercial drivers, they were not able to temper the design.”
Another added: “The architect was very focused on visualisations and not build-able details as that is what they thought the client required as this was the service they had provided previously.
“This architect didn’t have the required technical detailing that suited the fast-paced programme”
RIBA ambassador for collaboration Dale Sinclair described the results as “disappointing but no surprise”.
He said: “Architects frequently work for contractors after they have been novated to the role on design and build projects.
“As part of better conveying design status, novated architects need to disclose more detail on design risks with the contractor’s perspective in mind.
“What aspects of the design are robust? Where is further design development required? What aspects of the design have still to be drawn?
“Explaining the rules-of-thumb underpinning our work would communicate our designs better and allow the project team to make more considered decisions about cost and risk.”