Construction bidding is the process of submitting a proposal (tender) to undertake, or manage the undertaking of a construction project. The process starts with a cost estimate from blueprints and material take offs.
The tender is treated as an offer to do the work for a certain amount of money (firm price), or a certain amount of profit (cost reimbursement or cost plus). The tender, which is submitted by the competing firms, is generally based on a bill of quantities, a bill of approximate quantities or other specifications which enable the tenders to attain higher levels of accuracy, the statement of work.
For instance, a bill of quantities is a list of all the materials (and other work such as amount of excavation) of a project which have sufficient detail to obtain a realistic cost, or rate per described item of work/material. The tenders should not only show the unit cost per material/work, but should also if possible, break it down to labour, plant and material costs. In this way the individual who is selecting the tender will be quite confident that the tender is feasible. Bids are not only chosen on cost alone. Sometimes contractors submit lower tenders to win the contract and win the work. Either the costs that the contractor incurs are greater than the price he is charging the client (as a consequence of a lower tender determining the contract sum), and thus is likely to go insolvent, or he will claim for "loss and/or expense" due to discrepancies in the contract documents (this can be done deliberately). The lowest tender is not always a feasible tender. The lowest tender is the most likely to increase the contract sum the most throughout the course of the project.