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Last edited 15 Nov 2020
Quantity in a general sense is the amount of something that there is, was or will be. This amount may be measured in terms of number, weight, length, area, volume and time. For example, there were 50 accidents last year, or 2kg of flour will be required to make the cake. The same general sense may be applied to construction: the estate when completed will comprise 250 dwellings housing a maximum of 1,000 people.
A bill of quantities is a document prepared by the cost consultant (often a quantity surveyor) that provides project-specific, measured quantities of the items of work required to complete the project. These quantities are usually highlighted in the drawings and specifications that form part of the tender documentation.
Preparing a bill of quantities requires that the design is complete and a specification has been prepared. The bill of quantities is issued to tenderers to enable them to prepare a price for carrying out the works. The bill of quantities assists tenderers in the calculation of construction costs for their tender, and, as it means all tendering contractors will be pricing the same quantities (rather than taking off quantities from the drawings and specifications themselves), it also provides a fair and accurate system for tendering.
However, it is usually the case that during the construction period, the quantity surveyor prepares different forms of quantities by measuring and valuing the work carried out at regular intervals. These new quantities allow the client to accurately and fairly pay the contractor for the work completed.
In order to ensure cross-industry harmonisation, it is important that the way building quantities are measured is conducted on a consistent basis and allows the costs of different projects to be compared meaningfully. To achieve this, quantity surveyors can use standard ways to measure quantities. This includes the Standard Method of Measurement (SMM7) or New Rules of Measurement (NRM 2) and Agreed Rules of Measurement 4.
A development of the elemental cost plan of estimating construction project costs, approximate quantities form part of an approximate quantities cost plan which represents a first attempt to measure defined quantities from drawings (or to ‘take them off’)
An approximate quantities cost plan is part of the iterative cost planning process and is a development of the elemental cost plan. Unlike the elemental cost plan (in which the cost of elements is broken down from the overall construction cost, based on the experience of the cost consultant and known costs of similar completed projects), the approximate quantities cost plan is a first attempt to measure defined quantities from drawings. In effect, it is a costed approximate bill of quantities.
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