Design-Build Contract

A design-build contract appoints a single contractor to both design and construct a facility based on the owner's performance or output requirements, placing design risk and construction risk with one entity and enabling overlapping design and construction phases that can shorten delivery timescales.

What is a Design-Build Contract?

In traditional procurement, the owner appoints a designer separately, completes the design, then bids construction. In a design-build contract, the two phases are integrated: one contractor does both. The owner specifies what the facility must achieve (capacity, performance, quality standard) rather than how to build it. The contractor develops the design and constructs to that design, carrying liability for both. This is why design-build is closely related to the epc model; the FIDIC Yellow Book (Conditions of Contract for Plant and Design-Build) governs this structure in international procurement.

Design-build is used for buildings, transport infrastructure, water infrastructure, and process plant where the design can be meaningfully defined by performance outputs rather than detailed prescriptive specifications. Development banks including the World Bank and ADB allow design-build procurement for infrastructure projects under their Standard Bidding Documents. The overlap between design and construction that design-build enables, sometimes called "fast-track" delivery, can compress the programme compared to design-bid-build, which is attractive when delivery speed is a priority alongside cost efficiency.

The turnkey-contract extends the design-build concept to include commissioning and handover of an operational facility, while epcm contracts separate management from execution responsibility.

Why Design-Build Contracts matter for bidders

Design-build bidding requires contractors to carry a design team or a design sub-consultant from the proposal stage, adding cost and coordination complexity to the bid. Proposals typically include a preliminary design or design concept as part of the technical submission. Evaluation of design-build bids often combines technical assessment (design approach, methodology) with price, making the technical quality of the proposed design a competitive differentiator alongside cost.

FAQ

Which FIDIC book governs design-build contracts?

The FIDIC Yellow Book (Conditions of Contract for Plant and Design-Build, 1999 and 2017 editions) governs design-build contracts internationally, particularly for plant and process facilities.

Who is liable for design errors in a design-build contract?

The contractor is liable for design errors, since the contractor is responsible for both the design and the construction. This is the key risk shift from traditional design-bid-build procurement.

Can design-build contracts use a lump sum price?

Yes, and this is the most common structure. The integrated scope and single contractor accountability make fixed lump sum pricing appropriate when the employer's output requirements are clearly defined.