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 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 / the 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.