Definition
Contractor’s Designed Portion (CDP) refers to specific parts of the
construction works that the contractor is contractually required to design, in
addition to executing them, while the employer or its team handles the overall
design.
The contractor assumes full responsibility for these portions, including
fitness for purpose, coordination with other works, and compliance with
regulations and codes.
Examples of CDP
- Façade system design: The employer specifies the performance requirements, and the contractor designs the curtain wall, anchors, brackets, and interfaces with the structure.
- Steel connection design: The structural frame may be generally designed by the employer’s engineer, but the contractor designs the shop details and connection calculations.
- Precast concrete design: The employer defines the geometry and load requirements, while the contractor designs the lifting points, joints, and reinforcement details for fabrication.
- Temporary works with permanent influence: For example, the contractor may design retaining wall propping or embedded items that become part of the permanent works.
- Specialist roofing system: The employer specifies the required waterproofing performance, and the contractor designs the membrane build-up, fixings, and edge details.
Key Responsibilities
- Contractor must submit designs for approval, manage coordination (e.g., with services or structures), and obtain necessary consents like building regulations.
- Employer provides performance specs in Employer's Requirements; design team reviews but avoids liability for CDP.
- Differs from JCT Design & Build (full contractor design) or FIDIC Yellow Book (contractor-led design) as the contractor is only responsible for the design of parts of the scope not the whole works.
- Although the contractor takes on some design responsibility, a contract with a CDP element is still generally classified as a traditional contract rather than a full "design and build" contract (where the contractor would be responsible for designing the entirety of the project)
When a construction contract includes a CDP, the contractor assumes
additional obligations specifically related to their design work. These
obligations include:
- Professional Indemnity: An obligation to take out and maintain professional indemnity insurance
- Copyright Licence: Granting a copyright licence to the employer, which allows the employer to use the copyright material contained within the contractor's design for the CDP
- Warranty: Providing a warranty to the employer guaranteeing that the contractor will use an appropriate level of skill, care, and diligence when carrying out the design for the CDP