Design–bid–build (or design/bid/build, and abbreviated D–B–B or D/B/B accordingly), also known as Design–tender (or "design/tender") and traditional method, is a project delivery method in which the agency or owner contracts with separate entities for each the design and construction of a project.
Design–bid–build is the traditional method for project delivery and differs in several substantial aspects from design–build.
There are three main sequential phases to the design–bid–build delivery method:
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In this phase the owner retains an architect (or engineer for infrastructure works) to design and produce tender documents on which various general contractors will in turn bid, and ultimately be used to construct the project. For building projects, the architect will work with the owner to identify the owners needs, develop a written program documenting those needs and then produce a conceptual or schematic design. This early design is then developed, and the architect will usually bring in other professionals including mechanical, electrical, and plumbing engineers (MEP engineers), a fire engineer, structural engineer, sometimes a civil engineer and often a landscape architect to complete documents (drawings and specifications). These documents are then coordinated by the architect and put out for tender to various general contractors.
Bids (tenders) can be "open", in which any qualified bidder may participate, or "select", in which a limited number of pre-selected contractors are invited to bid.
The various general contractors bidding on the project obtain copies of the tender documents, and then put them out to multiple subcontractors for bids on sub-components of the project. Sub-components include items such as the concrete work, structural steel frame, electrical systems, and landscaping. Questions may arise during the tender period, and the architect will typically issue clarifications or addenda. From these elements, the contractor compiles a complete "tender price" for submission by the closing date and time. Tender documents can be based on the quantities of materials in the completed construction such as in the UK with bills of quantities, or the operations needed to build it as in operational bills.
Once bids are received, the architect typically reviews the bids, seeks any clarifications required of the bidders, ensures all documentation is in order (including bonding if required), and advises the owner as to the ranking of the bids. If the bids fall in a range acceptable to the owner, the owner and architect discuss the suitability of various bidders and their proposals. The owner is not obligated to accept the lowest bid, and it is customary for other factors including past performance and quality of other work to influence the selection process. The project is usually awarded to the lowest bid by a qualified general contractor.
In the event that all of the bids are in excess of the goals of the owner, the owner may elect to reject all bids. The following options become available:
After the project has been awarded, the construction documents may be updated to incorporate addenda or changes and they are issued for construction. The necessary approvals (such as the building permit) must be achieved from all jurisdictional authorities for the construction process to begin.
In most instances, almost every component of a project is supplied and installed by sub-contractors. The general contractor often provides work with its own forces, but it is not uncommon for a general contractor to limit its role to management of the construction process and daily activity on a construction site (see also construction management).
The architect acts as the owner's agent to review the progress of the work and to issue site instructions, change orders or other documentation necessary to the construction process.