Bidding 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 bid (or 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, HVAC, and landscaping. Questions may arise during the bid (or tender) period, and the architect will typically issue clarifications or corrections to the bid documents in the form of addenda. From these elements, the contractor compiles a complete bid (or "tender price") for submission by the established closing date and time (i.e., bid date). Bids can be based on the quantities of materials in the completed construction (e.g., as in the UK with
bills of quantities), the operations needed to build it (e.g., as in
operational bills), or simply as a lump sum cost; however, these bid requirements are elucidated within the bid documents. Once bids are received, the architect typically reviews the bids, seeks any clarifications required of the bidders, investigates contractor qualifications, 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. However, the project is typically awarded to the general contractor with the lowest bid. In the event that all of the bids do not satisfy the needs of the owner, whether for financial reasons or otherwise, the owner may choose to reject all bids. The following options become available to the owner: • Re-bid (or re-tender) the construction of the project on a future date when the owner's needs are met, such as when money becomes available and/or construction costs go down. • Abandon the project entirely. • Issue a work order to have the architect revise the design (sometimes at no cost to the Owner, if previously negotiated), so as to make the project smaller or more efficient, or reduce features or elements of the project to bring the cost down. The revised bid documents can then be issued again for bid (or re-tendered). • Select a general contractor, such as the lowest bidder, or an experienced cost estimator to assist the architect with design changes aimed at cost reduction. This process is often referred to as
value engineering. The revised bid documents can then be issued again for bid (or re-tendered). == Construction phase ==