Unlike design-build, the traditional design-bid-build approach entails two prime agreements with an owner for the delivery of a capital project. The first agreement is with an architect/engineer for the design of the project. The second contract is usually secured through a public bidding process with the lowest responsible bidder normally awarded the construction contract.
For example, if an owner wants to build a new water treatment plant using DBB, the owner issues a request for proposal (RFP) to engineering firms for the design services, selects the most qualified firm among those responding to the RFP, and negotiates a fee for such services. The engineering firm then develops the project design and bidding documents. Once a design has been accepted, the owner solicits sealed bids from construction firms to build the project utilizing the design produced by the previously selected architect/engineering firm. A construction contract is awarded to the lowest responsible bidder who has the responsibility to build the project and commission it prior to turning over to the owner for long-term operations.
Design-build allows the owner to contract with a single entity for both the design and construction of the project.