Last edited 22 Aug 2018

Design and build - pros and cons


Design and build is a term describing a procurement route in which the main contractor is appointed to design and construct the works, as opposed to a traditional contract, where the client appoints consultants to design the development and then a contractor is appointed to construct the works.

Design and build can be advantageous in terms of time and allowing the overlap of design and construction to reduce the overall project delivery time. As the contractor is responsible for the design, time can be saved by running design and building elements concurrently.

The fact that there is a single point of responsibility for the client to deal with once the contract is awarded also makes things simpler. The client is also able to engage with the contractor and their design team or supply chain earlier in the design process to try and achieve a more practical solution if necessary.

In terms of cost, it allows the client a certain amount of control since lump sum or guaranteed maximum price contracts mean that the contractor agrees to take on the responsibility for the design and construction for a pre-agreed price. The contractor takes on much of the financial risk that is inherent in the project which lowers the risk, for example, of labour and material rises, for the client. It may also enable overall costs to be reduced as contractors may be able to design specialist elements at lower cost than professional suppliers or consultants.

The client will have reasonable price certainty if the design remains largely unchanged throughout the project. The contractor may want to make variations at certain points, and by calculating from a lump sum it should be relatively easy, not just to arrange the changes in the design but also to estimate how these changes will affect the overall costs.

Another advantage is that design and build provides the ability to novate the design team to the contractor, which can benefit quality. This can be beneficial to clients as it maintains continuity between pre-tender and post-tender design whilst leaving sole responsibility for designing and building the project with the contractor. For more information, see Novation.

There are some disadvantages to the design and build procurement route. In terms of quality, the contractor may exploit a specification that is open to interpretation and propose the cheapest route, which can lead to low quality products and build quality. This can mean that quality may be compromised if the employer’s requirements do not adequately ensure the specifications are adhered to. There can also be the problem that arises from the fact that builders are not architects and may not be expert in the latest legal and design requirements of new-builds. A poor design that is completed by a non-architect, could affect the buildability of the project.

There is also the risk that the client may have to pay more if the contractor has to take on an unreasonably high level of risk due to a lack of design clarity when tendering. In terms of design flexibility, it is also important to consider that any request for changes will have cost and time implications.

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