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Last edited 24 Sep 2020
Design and build: detailed design (design by contractor)
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.
In this option, 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 Principal Designer as this role 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 who 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.
For design and build projects where the detailed design is carried out by the consultant team, see: Design and build: detailed design (design by consultant team).
 Starting the work stage.
The client updates the project execution plan to reflect comments made at the end of the previous stage. The contractor co-ordinates a start-up meeting attended by the client to receive comments made at the end of the previous stage, and to discuss procedures and the programme for the stage.
The client may identify a requirement to appoint additional independent client advisers (in particular if the consultant team has been novated or switched to the contractor), an employer's agent to administer the contract or party wall surveyor(s). Go to work stage: Design and build: appointment.
 Developing detailed design options
The contractor co-ordinates the development of a detailed design based on the concept design and co-ordinates consultations about the functional aspects of detailed design with the client's user panels and champions, and if necessary external stakeholders.
 Developing the outline specification.
The contractor co-ordinates the sourcing of materials, components and assemblies identified within the employer's requirements as to be submitted for comment by the client. NB there is no provision for the client to reject items unless they are inconsistent with the employer's requirements. Any other instructions would constitute a change which 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. Additionally, the client should be wary of 'approving' contractor proposals as this might be deemed to relieve the contractor of their liability for those items.
 Developing the detailed design.
The contractor arranges a design review of the detailed design and outline specification and then develops the detailed design and outline specification to take on board comments made. The contractor updates the elemental cost plan and cash flow projection.
The client considers the contractor's design documents (if required) 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.
If required by the employer's requirements the contractor makes 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 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 prepared.
The contractor issues tender documentation to prospective tenderers and co-ordinates the review of submitted tenders. The contractor 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.
 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. This can only be done in relation to compliance with the employer's requirements.
The contractor co-ordinates amendment of the technical design in line with comments made during the design review, 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. This can only be done in relation to compliance with the employer's requirements.
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