A recent judgment by the Technology and Construction Court in MJS Projects (March) Ltd v RPS Consulting Services Ltd [2025] EWHC 831 (TCC) has shed light on the scope of design liability in design and build contracts, emphasizing the distinction between negligent design and defective construction.
The dispute arose from the development of a container park near Felixstowe Port. MJS Projects, acting as the main contractor under a JCT Design and Build contract, subcontracted design duties to RPS Consulting Services. Within months of completion in 2017, concrete deterioration around three slot drains led to legal action.
MJS alleged the damage stemmed from RPS’s negligent design, particularly errors in load calculations and dowel placement. However, the court found that while the actual construction deviated from the design—using incorrect dowel sizes and positioning—the root cause of the failure was poor construction, not flawed design.
Expert testimony played a central role, with the court reviewing technical evidence on dynamic loading, joint performance, and the necessity of mass concrete tapers. Although both parties acknowledged construction errors, RPS maintained that these caused the damage and not any design flaw—a position the court ultimately accepted.
Her Honour Judge Kelly ruled that RPS’s design met the contractual standard and was not negligent. Attempts by RPS to shift blame to MJS for inadequate supervision of subcontractors were dismissed due to insufficient pleading.
The judgment reinforces the importance of proper construction practices and highlights that liability does not automatically transfer to designers when implementation is faulty. It also underscores the benefits of early dispute resolution methods, such as adjudication or mediation, in managing complex technical disagreements.
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