Design by Contract

When someone says, "You're D&B," what does that actually mean?

A design does not fit. A client asks for something different. A consultant says it was always required. A drawing has been reviewed or approved. A subcontractor says it designed what it was given. Then somebody points at the contractor and says: "You're Design and Build."

But that does not answer the important questions.

Which design? Which requirement? Which document? Which version? Who created it? Who accepted responsibility for it? Was it part of the original bargain, a later change, a correction, a statutory requirement or simply somebody's preferred solution? And ultimately, who carries the time, cost and consequence?

Design by Contract is a practical examination of how design responsibility is really created, transferred, developed and disputed on construction projects.

Thomas Marriner follows design responsibility from the information that exists before the contractor arrives, through Employer's Requirements, Contractor's Proposals, tender qualifications, amendments, novation and consultant appointments, into design development, coordination, technical review, approval, change, conflicting documents, precedence and finally recourse when something goes wrong.

The central idea is simple:

Design responsibility is not determined solely by who drew the drawing. It is determined by the promises the parties actually made.

That matters because modern projects rarely have one designer. Architects, engineers, contractors, specialist subcontractors, manufacturers, consultants and clients may all contribute to the finished solution. The contractor may inherit design it did not create, coordinate information produced by others and accept obligations that are wider than its own authorship.

The book shows how to work out what those obligations really are.

A recurring ceiling-void problem runs through the book: inherited design, tender derogations, contractor coordination, employer-side review, a later client request and the familiar argument over whether the solution is a contractor correction or a change. Rather than offering a simplistic answer, the book builds the evidence needed to decide the position properly.

Along the way, it introduces a practical set of analytical tools including Contractual Gravity, Requirement Migration, the Five-Position Design Map, the Three-Promise Model, the Mirror Gap, the Approval Effect Test and the Contract State Register. These are not new administrative burdens. They are ways of asking better questions of the documents and decisions a project already has.

This book is written for Project Directors, Construction Directors, Commercial Managers, Quantity Surveyors, Design Managers, Technical Managers, Project Managers, Contracts Managers, Preconstruction teams, Estimators, consultants, Employer's Agents, client representatives and specialist subcontractors - anyone who has to understand, price, administer or deliver Design and Build responsibility in the real world.

If you have ever heard:

"You're D&B."
"It was on the tender drawings."
"Your consultant designed it."
"The client approved it."
"Building Control accepted it."
"That isn't a change."
"It was always in the specification."
"Just get on with it and we'll sort the money later."

- then this book is written for you.

Design by Contract is not a construction-law textbook and it is not a substitute for project-specific legal advice. It is a practical construction book about understanding the bargain before you have to reconstruct it under the pressure of a claim.

Because saying "it depends on the contract" is only the beginning.

The useful skill is knowing what to look at next.