The UK Design & Construct PI Guide: Contractors With Design Liability

The moment a contractor takes on design, it takes on a professional indemnity exposure its liability policies won’t touch. This guide covers the D&C essentials, from fitness for purpose to novation.

Why contractors need PI at all

Traditional contracting kept a clean divide: consultants designed, contractors built, and each insured accordingly. Design and construct procurement erased that divide. Under a D&C contract the contractor takes responsibility for the design — whether produced by its in-house engineers, by sub-consultants it appoints, or by a novated design team it inherits from the employer. Design responsibility means design liability, and design liability is a professional indemnity exposure that a contractor’s public liability and contract works policies simply do not cover: they respond to injury and physical damage, not to the pure financial cost of a design that is wrong.

Any contractor signing a D&C contract, a design-portion supplement, or even taking informal design decisions on site (“we’ll detail that connection ourselves”) is carrying PI exposure and needs cover shaped for it.

How D&C PI differs from architect and engineer PI

A contractor’s D&C policy is a different animal from the annual policy an architect or consulting engineer buys, in several ways that matter at claim time:

• What counts as the professional activity. A consultant’s policy covers a firm whose entire output is design. A contractor’s policy has to isolate the design element inside a business that mostly builds — wordings differ on how they treat design carried out by sub-consultants, design checking, temporary works design and workmanship that shades into design choice.
• The costs that flow from a design error. On site, a design defect usually surfaces as a physical problem needing rectification. Whether a D&C wording covers the costs of re-doing work, and how it draws the line between design failure (covered) and poor workmanship (not), is the most litigated boundary in this class. Read the rectification and mitigation provisions with care.
• Interface with other project insurance. D&C PI has to sit coherently alongside contract works, latent defects and the consultants’ own policies. Consultant PI rarely needs this choreography.

Fitness for purpose versus reasonable skill and care

This distinction decides more D&C insurance outcomes than any other. As a matter of general law, a professional designer’s default obligation is to exercise reasonable skill and care — to perform to the standard of a competent member of the profession. A contractor supplying a completed thing can, by default or by contract, take on the stricter obligation that the result will be fit for its intended purpose — a promise about outcome, not effort. The gap between them is stark: under fitness for purpose you can be liable even though nobody was negligent, because the building simply doesn’t perform as promised.

The insurance consequence is equally stark. PI policies are negligence-based: they generally respond to failures of reasonable skill and care, and commonly exclude liability assumed only because a contract promised a guaranteed outcome. A contractor who signs a fitness-for-purpose design obligation may therefore hold liability its PI does not cover. The practical defences are contractual: negotiate design obligations down to reasonable skill and care, hunt for fitness-for-purpose language hiding in performance specifications, employer’s requirements and warranty schedules, and where such an obligation is commercially unavoidable, make sure everyone prices the uninsured residue knowingly.

Collateral warranties and third-party rights

D&C projects generate paper: collateral warranties (or third-party rights schedules) in favour of funders, purchasers and tenants, each extending your design duty to someone who isn’t your client. Every warranty you sign widens the population who can claim against your PI. Three checks before signing: that the duty warranted does not exceed the duty in the underlying contract (watch for fitness-for-purpose creep); that any insurance-maintenance clause — typically requiring PI at a set limit for a set period after completion — is something you can actually sustain; and that step-in and assignment provisions don’t multiply beneficiaries beyond what was priced. Keep a register of every warranty given; at renewal your broker needs it.

Novated design teams

On many D&C schemes the employer’s architects and engineers are novated to the contractor at contract award: the designers who once worked for the employer now work for you, and their past design becomes part of the design you are responsible for delivering. Novation questions worth resolving in the documents rather than in litigation: whether the consultants owe you a duty in respect of their pre-novation work; whether their own PI is adequate and maintained, since your first recovery route for their errors is against them; and how the novation agreement allocates responsibility for reviewing and adopting the earlier design. A contractor is well advised to collect evidence of each novated consultant’s PI, on sensible limits, as a condition of the novation.

Single-project versus annual cover for D&C

A contractor with a steady flow of design responsibility usually carries an annual D&C PI programme sized for its typical book. Project-specific PI earns its place when a particular scheme is far larger than the normal run of work, when the employer or funder demands a dedicated policy with a ring-fenced limit, when the job sits in a special purpose vehicle or joint venture with no annual programme of its own, or when the required post-completion maintenance period is long enough that relying on year-by-year renewals feels fragile. The two can also combine — annual cover for the ordinary book, a project policy for the outlier — and the right structure is worth deciding before the contract fixes the insurance clause.

Placing D&C PI well

Insurers will want your design turnover as distinct from build turnover, the split of in-house versus sub-contracted design, your sectors and methods, warranty commitments, and your procedures for design review and sign-off. Presenting that clearly is most of the battle. Apex is an independent FCA-authorised broker with a construction professional-risks practice; if you are pricing a D&C tender or renewing a contractor’s PI programme, we can review the contract’s insurance and design obligations alongside the placement itself.

Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This page is general information, not advice; policy terms always take precedence.