Difference between “Design & Build” & “Design-Bid-Build”

Design & Build and Design-Bid-Build are two very different construction delivery methods used in today’s construction society.

Design & Build

Design & Build is a method to deliver a project in which the design and construction services are contracted by a single entity known as the design-builder. Design–Build relies on a single point of responsibility contract and is used to minimize risks for the project owner and to reduce the delivery schedule by overlapping the design phase and construction phase of a project.

Currently in the Singapore context, there are two main types of Design & Build methodology – Contractor-led Design-Build & Architect-led Design-Build.

Contractor-Led Design-Build

In contractor-led design–build projects, the organization is structured in a way that the owner works directly with a contractor who, in turn, coordinates subcontractors. Architects contribute to contractor-led design–build projects in one of several ways, with varying degrees of responsibility.


1. Architect as employee of contractor

The architect works for the contractor as an in-house employee. The architect still bears professional risk and is likely to have less control than in other contractor-led design–build approaches.

2. Architect as a subcontractor

Here, the architect is one of the many subcontractors on the team led by the contractor. The architect bears similar professional risk but still with little control.

3. Architect as second party in contractor-led integrated project delivery

The architect and contractor work together in a joint venture, both coordinating the subcontractors to get the project built. The building owner has a single contract with this joint venture. The contractor leads the joint venture, so when supervising the subs, the architect might defer to the contractor. The architect bears the same risk as they do in the traditional approach but has more control in this project delivery, even if they were to defer to the contractor.

In the Contractor-Led Design-Build projects, architect may face a limitation in design and thus compromising the aesthetic value of the project.


Architect-Led Design-Build


Architect-led design–build projects are those in which interdisciplinary teams of architects and building professionals collaborate in an agile management (iterative, incremental method) process, where design strategy and construction expertise are seamlessly integrated, and the architect, as owner-advocate, ensures high fidelity between project aims and outcomes.


Design-Bid-Build is a traditional method for project delivery and the owner contracts separately with a designer and a contractor. The design firm is hired to deliver 100 percent complete design documents. The owner or agent then solicits fixed price bids from contractors to perform the work. Designers and contractors bear no contractual obligation to one another and the owner bears all risk associated with the completeness of the design documents.

There are three main phases to Design-Bid-Build Method:

Design Phase

Architect is to design and produce tender documents which include construction drawings and technical specifications according to owner’s need. Other building professionals may be brought in by the architect to assist in completing the construction drawings and technical specifications. Architect will compile the relevant tender documents and issue to tenderers (general contractors) during the tender phase.

Tender Phase

Architect will issue clarifications or corrections to the tender document if there are any questions from the tenderers. Tenderers will compile a complete tender price for submission before the closing date. Architect will review the tenders and seek any clarification if needed. Architect will then advise the owner regarding the selection of contractors. If the owner is not satisfy with the bids, the owner may choose to reject all bids. The owner can either

  • Re-bid or Re-tender
  • Abandon the project entirely
  • Issue work order to have architect revise the design

Construction Phase

Architect acts as the owner’s agent tor review progress of the construction work. Builders are to construct the project according to the tender document. Thus, changes of design during the construction phase is not recommend as there might be cost incurred.

In summary,

The Traditional Approach

Step 1. Look for an Architect/Designer to begin the Project.

Step 2. Architect advises on Design and Brief Formulation of Concept.

Step 3. Design is finalized with Architect, and approval is sought from relevant Authorities.

Step 4. Architect prepares tender for Contractors to bid on.

Step 5. Builder with a competitive bid is selected to commence Construction Works.

Step 6. Construction Work commences.

Step 7. Architect/Owner monitors progress of works and ensures budget is kept to.

Step 8. Owner to make decisions with regards to material selection for cost considerations.

Step 9. Alterations as required by the Owner.

Step 10. Project Completion.

The Design|Build Approach

Step 1: Look for a Design|Build firm to begin the Project.

Step 2: D|B firm works with owner to develop Design and Brief Formulation of Concept.

Step 3: Design is finalized and approval is sought from relevant Authorities.

Step 4: Construction commences with no variations or changes to the Costs or Plans as specified.

Step 5: Unless new alterations required by Owner, Project Completion.