4: Technical design

The technical design stage (sometimes referred to as ‘design’) develops the design in sufficient detail for co-ordination to be completed and enables packaged, production information to be prepared which can be passed to the contractor and their supply chain to construct the development. It should also allow applications for statutory approvals to be completed. Increasingly, technical design involves design undertaken by specialist subcontractors.

The employer should develop their strategies for occupation of the completed development during this stage and the project management plan may be reviewed and revised.

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Employer’s information requirements and master information delivery plan

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Both the employer’s information requirements and consequently the master information delivery plan should be reviewed and revised to outline the requirements and plan to deliver information needed to manufacture, procure, schedule, cost, build, and install elements, systems and parts.

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Technical design

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The supplier co-ordinates the appointment of specialist subcontractors to assist in the preparation of the technical design. This should include an assessment of their BIM and IT capability and capacity, which may reveal the need for training. It may be appropriate to arrange visits to the specialist subcontractors' premises to assess samples or mock-ups and to witness tests.

If they do not already have one, the supplier may appoint a design co-ordinator with specific responsibility for co-ordinating and integrating specialist subcontractors' designs.

Specialist designs should be incorporated into the developing project information model. Model files with generic objects should be progressively replaced with more specialist models containing specific objects with specifications and method statements attached, along with information about space allocation for operation, access, maintenance, installation, replacement and so on. This may require a 'change of ownership' procedure for those parts of the model.

Clash detection simulations should be undertaken. Other model simulations may also be undertaken to demonstrate compliance with remaining building regulations and other statutory approvals, such as structural performance, energy use, acoustic performance, fire and smoke modelling and evacuation modelling.

Packages of work should be identified and critical interfaces highlighted. Production level models with embedded specification should be developed that will allow tenders to be obtained from contractors (or their supply chain if the contractor has already been appointed) and may be used for fabrication, co-ordination, sequencing and estimating.

The construction sequence should be developed in detail and may define crane zones and lifting operations, formwork, access details, construction sequences and movements and logistics. This should be linked to a project management scheduling tool to co-ordinate the works. As part of this, there should be a particular emphasis on equipment with long manufacturing times such as; switchgear, chiller units, lifts, escalators and bespoke cladding systems, some of which may justify early ordering. In addition, there may be front-end construction work such as; service diversions, demolition, setting out , underground drainage, piling and other groundworks that merit placing preliminary contracts.

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Cost plan

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The elemental cost plan should be developed into an approximate quantities cost plan which may be produced from the model, accompanied by a schedule of assumptions made and a cash flow projection. A pre-construction whole-life cost plan may be prepared. If necessary a value management exercise may also be undertaken.

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End of stage report and information exchange

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An end of stage report is prepared identifying key issues as well as details of packaging, long lead time items and preliminary contracts.

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.

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Employer’s decision point:

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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.

Plain language questions	Information required
Is the information compliant with employer's information requirements? Has the work of specialist subcontractors been properly co-ordinated? Are there works that should be procured separately from, or in advance of, the main works? Have statutory approvals been completed? Is the project affordable? Are funds available? Should funds be committed for construction?	Native and industry foundation classes (IFC) building information model files. COBie file. Updated employer's information requirements. Updated project management plan. Specification. Approximate quantities cost plan Project programme. Drawings and reports.

If a supplier has not already been appointed to construct the development, it will now be necessary to prepare tender documentation and a pre-tender estimate and to tender the construction contract.

If a suppler has already been appointed to construct the development, they will have to appoint their own supply chain, which will involve preparing tender documentation, including their own version of the employer’s information requirements, and assessing cases in which they may want to procure information other than that required by the employer.

In addition, the employer may award separate occupation services contracts for delivering and installing equipment, fixtures and furniture (sometimes from other premises) outside of the main contract. This may also pick up small building changes to be instructed outside the main contract. It is important that these suppliers have a proper understanding of the development and its operation and that the information they generate is consistent with the employer's information requirements.

For a description of the process necessary to appoint a supplier see 1c: Preparation and brief (supplier appointments).

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Next stage >> 5: Construction.

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--Cohesive