The main use of a bill of quantities in support of a contract is the traditional and proven means of securing a lump-sum price for carrying out the building works for the client. SC Quantity Surveyors produce several types of Bill of Quantities which include :
- Firm (to obtain a lump-sum price for a fully designed building project)
- Approximate (subject to re measurement as built)
Firm Bill of Quantities
The reliability of the tender price will increase in relation to the accuracy of the quantities provided (i.e. the more precisely the work is measured and described). Provided there were no design changes, then firm bills of quantities would provide a price at tender stage, which would equal the final cost. However, there will be changes, and the bill of quantities provides a good basis for cost control, since the direct cost can be assessed with reference to the bill of quantity rates. In general the firmer the bill of quantities the better it is as a means of financial control.
Approximate Bill of Quantities
SC Quantity Surveyors can produce approximate bills of quantities which are mainly used when there is insufficient details to prepare firm bills of quantities or where the client has decided that the time and cost of a firm bill of quantities is not warranted. These types of contracts do not provide a lump-sum price, but instead tender price totals (ie. a quantified schedule of rates), since the quantities are subject to re-measurement on completion by the quantity surveyor. In general these contracts are usually subject to greater variation than lump sum contracts and therefore should only be used where time is a limiting factor or where there is great uncertainty in respect of certain elements, such as major excavations and earthworks.
It is important to note that the initial resource cost of approximate bills of quantities is likely to be lower than firm bills of quantities, but the need for re-measurement invariably results in an overall higher resource cost. Although the measured quantities are approximate, the descriptions of work items should be correct in the approximate bill of quantities
A bill of quantities or contract bills is also a written document providing fundamental information about a proposed project, but varies from a specification in that it arranges the information into a form more suitable for direct pricing by a builder or contractor. Bills of quantities are used for larger and more complicated contracts, and are prepared within the organisation of a Design Team by a quantity surveyor using the information supplied by production drawings and specification notes. A currently acceptable method of presentation for bills of quantities consists of three main parts:
- Preliminaries: as described for specifications.
- Preambles to trades: a general specification and description of materials and standards of work.
- The quantities: a description of the individual items to be priced and also the numbers, amounts or quantities of each required for the project.