3: Developed design

Developed design (sometimes referred to as 'detailed design' or ‘definition’) develops the concept design into a dimensionally correct and co-ordinated design, describing all of the main components of the building and how they fit together. It should provide sufficient information for applications for statutory approvals to begin.

It may be useful to consult with specialist subcontractors during this stage to begin to address specific technical aspects of the design that will be developed fully in the next stage.

Employer’s information requirements and master information delivery plan

The employer’s information requirements and the master information delivery plan should be reviewed and revised at the start of the stage. They will develop to outline the requirements and plan to deliver information needed for statutory approvals and to build and install elements, systems and parts.

Developed design

The supplier co-ordinates the development of the design based upon the approved concept design. The spatial coordination and information exchange processes described in PAS 1192-2 should be adopted to ensure the design team shares and coordinates information effectively.

The supplier develops the project information model in accordance with the master information delivery plan. They may also develop other information they have identified as important through the course of their activities.

The project information model is developed based upon generic representations with approximate quantities, size, shape, location, tolerances and so on.

Specification properties and attributes are developed so that the selection of systems and products is possible. Where the employer has already specified that certain building products should be used, or where there are key components that have already been selected, these may be incorporated into the model.

Structural information and architectural information should develop in detail, and services design may include generic information about sizes, capacity and control systems. The model may allow early contractor engagement, and an outline construction sequence may be developed. Plans, cross sections, elevations, and visualisations may be produced as well as schedules of facilities.

Clash avoidance (rather than detection) should be a continuous part of the process. Software-driven clash detection can provide a safety net, but should not be used as a substitute for careful design.

The supplier should consult with specialist subcontractors regarding important technical aspects of the design. They should also consult the employer and other stakeholders about functional aspects of the design.

The design is amended and developed based upon the outcome of consultations that have taken place.

Statutory authorities

The supplier should consult the statutory authorities to establish requirements for approvals (such as building regulations approvals), including the preferred form and content of submissions. An approved inspector may be appointed to consider building regulations submissions rather than making submissions to a local authority inspector, and in this case, the appointment process should include assessment of the inspector's BIM capability.

Cost plan

The elemental cost plan should be updated from the model, accompanied by a schedule of assumptions made and a cash flow projection. A detailed assessment of whole-life costs might also be undertaken. If necessary a value management exercise may be undertaken.

End of stage report and information exchange

The supplier prepares an end of stage report summarising key issues, identifying risks, identifying products that have been selected, any performance specified work and the requirement for design by specialists. The report may include a developing soft landings strategy and might summarise the outcome of consultations, such as the likelihood of receiving building regulations approval.

The supplier prepares an information exchange (or 'data drop') as required by the employer's information requirements. This involves issuing published information into the employer's information environment.

Employer’s decision point

The table below sets out examples of plain language questions that an employer might ask at this decision point and the information they might require to answer those questions.

Next stage >> 4: Technical design.

--Cohesive