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Last edited 01 Oct 2020
Design and build: detailed design (design by consultant team)
This stage is concerned with developing the detailed design and technical design for the project. It is also likely to include making a detailed planning application and applications for statutory approvals.
The tasked below are based on a project where the detailed design is prepared by the consultant team up to technical design, and is then taken on by the contractor. For projects where the detailed design is undertaken by the contractor, see: Design and build: detailed design (design by contractor).
 Starting the work stage.
The client updates the project execution plan to reflect comments made at the end of the previous stage. The lead consultant co-ordinates a start-up meeting attended by the consultant team and the client to issue revised documentation and to pass on comments made at the end of the previous stage, discuss the procurement strategy for the project and to agree the programme for the stage.
The consultant team or the client may identify a requirement to appoint additional consultants, such as an approved inspector or party wall surveyor(s). Go to work stage: Design and build: appointment. If an approved inspector is appointed, the client and approved inspector must jointly issue an 'initial notice' to the local authority. Unless the local authority reject the initial notice, responsibility for verifying that the project complies with the building regulations will then fall to the approved inspector.
 Developing detailed design options.
The lead designer co-ordinates the development of a detailed design based on the approved concept design and co-ordinates consultation about the functional aspects of the detailed design with the client's user panels and champions, and if necessary external stakeholders.
The lead designer co-ordinates consultations with statutory authorities, non-statutory authorities, insurance providers, neighbours etc. The client may need to issue party wall notices and to appoint party wall surveyor(s). Go to work stage: Design and build: appointment.
 Developing the outline specification.
- The client identifies requirements for equipment to be provided within the main contract, or equipment which has installation requirements to be provided within the main contract.
- The lead designer co-ordinates the sourcing of materials, components and assemblies for approval by the client.
- The lead designer co-ordinates the identification of requirements for design by specialist contractors.
 Developing the detailed design.
The lead designer co-ordinates the consultant team to undertake a design review of the detailed design and outline specification and then develop the detailed design and outline specification to take on board comments made. The cost consultant updates the elemental cost plan and cash flow projection.
The lead consultant presents the final detailed design to the client and requests approval to appoint specialist contractors and if necessary to make a detailed planning application (or reserved matters applications if a previous application was made for outline planning permission). Go to work stage: Design and build: planning permission (design by consultant team).
The client may wish to appoint additional independent client advisers, in particular if the consultant team has been novated or switched to the contractor. Go to work stage: Design and build: appointment.
NB from this point onward, all design development is attributed to the 'contractor'. The different disciplines working for the contractor (such as architects or engineers) are not separately identified. We do continue to identify the specific role of the principal designer as this is a requirement of the CDM Regulations. Any design reviews carried out on behalf of the client (or any other advice given to the client) is attributed to independent client advisers. Independent client advisers may previously have been members of the consultant team or could be new appointments if the consultant team have been novated or switched to the contractor.
 Appointing specialist contractors to assist in the technical design.
If appropriate, the contractor advertises the specialist contracts and prepares and issues pre-qualification questionnaires. It may be appropriate to hold pre-tender interviews with prospective tenderers. A short list of prospective tenderers is then by prepared.
The contractor issues tender documentation to prospective tenderers and co-ordinates the review of submitted tenders. The contractor assesses the financial offers of tenderers and carries out financial checks to ensure the contract is within the financial capability of the tenderers (ideally the contract should not be more than 20% of the annual turnover of the tenderer). Interviews may be carried out if necessary.
If necessary, based on the price of the tenders received, the contractor may need to amend the design and seek revised tenders, or to carry out a value management exercise, amend the design and seek revised tenders (this may require agreement by the client).
 Preparing the technical design.
The contractor co-ordinates the preparation of the technical design including the incorporation of design by specialist contractors. The contractor may wish to appoint a design co-ordinator to be responsible for the co-ordination and integration of the technical design.
The contractor co-ordinates a design review of the technical design and, if appropriate, arranges visits to specialist contractors' premises to assess samples or mock-ups and to witness tests. Where appropriate, the contractor obtains samples for client comment. NB This can only be done in relation to compliance with the employer's requirements. Comments which amount to a change in the employer's requirements must be consented to by the contractor (although this consent may not be unreasonably withheld) and may result in an adjustment to the contract sum and a claim for extension of time.
The contractor co-ordinates amendment of the technical design in line with comments made during the design review and develops the elemental cost plan into an approximate quantities cost plan and revises the cash flow projection.
 Preparing a detailed design report.
The contractor co-ordinates consultations with the statutory authorities to establish submission requirements for statutory approvals. The contractor may appoint an approved inspector to consider building regulations submissions (rather than making submissions to a local authority inspector).
The client considers the contractor's design documents and comments within the specified time, either accepting, making comments or rejecting the contractor's design documents. NB This can only be done in relation to compliance with the employer's requirements. Comments which amount to a change in the employer's requirements must be consented to by the contractor (although this consent may not be unreasonably withheld) and may result in an adjustment to the contract sum and a claim for extension of time.
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