A game of two halves

Specifying design-and-build projects can be very complex or very simple, depending on the form of contract, the relationship of the parties carrying out the work, the complexity of the project, and other such factors. In reality, however, the basics required to complete a building project do not change: the client determines the need and use, the designer produces a solution and the builder makes that solution reality.

The attraction of design and build for the client is that it has a single point of responsibility (usually the builder) that generally offers a fixed price and "guaranteed" completion date very early in the design and construction process. The builder is able to make such a commitment because its risk is severely reduced. This is because it is able to "control" the design, or, to be more precise, manipulate the design in order to ensure timely completion and make a profit.

To the independent designer, this process is often seen as a way of reducing the dependency on good design. Ultimately, however, it is the client's decision. Design and build can produce good buildings but the opportunity to "down-spec" presents itself very easily and, in the end, quality can suffer if not controlled properly.

The type of specification required depends on which side of the fence specification writers find themselves. Generally, there are two sets of documentation included in any design-and-build contract: the employer's requirements and the contractor's proposals, both of which may include a specification of some sort. This is true whether the whole project is design and build, or whether specialist trades within a project are to be provided on this basis using, for example, the Contractor's Design Portion Supplement in JCT98.

The employer's requirements can be a general statement that simply states location, size, use and financial restraints. This allows the tenderer to produce a design solution from scratch. But they can also be specific, providing a design that has to be maintained and completed by the contractor. It is fashionable on many such projects for a client to employ an architect to obtain planning permission, produce a schematic design for tender and then novate its services to a selected contractor in order to maintain the benefits of single-point responsibility. Traditional design-and-build contractors, however, offer a "seamless" service using an in-house design team or a firm with which they work continuously. The novated solution is a little like an arranged marriage, but at least the client is not subjected to disputes and doesn't have to pay for the divorce.

•  Outline specs should help the design-and-build tenderer understand the design intent
•  Post-contract, specifiers must make sure the spec does not bust the budget or the programme

So, where do specifications fit into all of this? If the employer's requirements include a partially complete design, an outline specification is usually required. In this document, the specifier should ensure that the tenderer has sufficient information to enable it to understand the design intent. This can be a general description of elevations or systems, plus typical design detail, material selection and performance criteria. As in all tender submissions, the better the information available at the time of tender, the better the chance of maintaining design intent.

The contractor's proposals should incorporate all the stated requirements and provide further details plus product names to reassure the employer that the project will meet its needs. When the employer's requirements are general, the contractor must produce a design and select systems and products in order to achieve the stated criteria for agreement before contract award.

In any design-and-build contract, detailed post-contract specifications are required to provide the builder or the subcontractors with the information necessary to carry out the work. Here, the specifier's role changes because he or she is often obliged to ensure that the specification does not compromise the programme or exceed the cost limits agreed in the contract. These specifications have little contractual significance and may deliberately be left loose to afford the builder a certain amount of flexibility. Certainly, clauses that are onerous in terms of levels of workmanship are often resisted. Where the services of an architect have been novated to the contractor, trouble can arise because the designer fights to maintain design intent while the contractor tries to find cheaper and quicker solutions that, in the opinion of the architect, compromise the design.