Willis's Elements of Quantity Surveying
This edition begins with an overview of the need for measurement and the differing rules governing measurement at different stages of the design or project cycle. As in previous editions the focus remains the detailed measurement of building elements, but the text has been fully revised in line with the NRM2 rules. A range of new and revised examples illustrating the use of NRM2 rules are a key feature of the book, which concludes with guidance on how to use the data collected during the measurement process to create the tender documents.
In the 12th edition the hallmarks of previous editions – clarity and practicality – have been maintained while ensuring the book is fully up to date, providing the student of quantity surveying with a first class introduction to the measurement of building elements.
Sandra Lee is Head of Product Development at the College of Estate Management in Reading.
William Trench is an Associate Tutor for the College of Estate Management, Reading.
Andrew Willis is Regional Managing Director at Franklin and Andrews, London.
Willis's Elements of Quantity Surveying
Method of analysing cost
It is evident that if a building is divided up into its constituent parts, and the cost of each part can be estimated, an estimate can be compiled for the whole work. It was found in practice that by making a schedule setting out the quantity of each item of work for a project, the labour and material requirements for these could be more readily assessed. This schedule at RIBA stage 5 can be in the form of a bill of quantities which, when priced by a contractor, provides a tender sum for a project. It must not be forgotten that a traditional bill of quantities only produces an estimate. It is prepared and priced before the erection of the building and gives the contractor s estimated cost. Such an estimated cost, however, under the most commonly used construction contracts, becomes a tender and a definite price for which the contractor agrees to carry out the work as set out in the bill. The bill must, therefore, completely represent the proposed work so that a serious discrepancy between actual and estimated cost does not arise.Origin of the bill of quantities
Competitive tendering is one of the basic principles of most classes of business, and if competitors are given comprehensive details of the requirements it should be fair to all concerned. However, historically when tendering based on drawings and specification, builders found that considerable work was involved in making detailed calculations and measurements to form the basis for a tender. They realised that by getting together and employing one person to make these calculations and measurements for them all, a considerable saving would be made in their overhead charges. They began to arrange for this to be done, each including the surveyor s fee for preparing the bill of quantities in their tender, and the successful competitor paying. Each competing builder was provided with the same bill of quantities which could then be priced in a comparatively short space of time. It was not long before this situation was realised by the architect and employer. Here the employer was paying indirectly for the quantity surveyor through the builder, whereas the surveyor could be used as a consultant if a direct appointment was made. This would give the employer greater control over the amount paid to the surveyor and the opportunity to increase the service that was provided. In this way, the quantity surveyor began to get the authority of the employer and was employed to prepare a bill of quantities for tendering purposes.The measurement process
The main purpose of a bill of quantities is therefore for tendering. Each contractor tendering for a project is able to price the work on exactly the same information with a minimum of effort. This gives rise to the fairest type of competition.
Despite the demise of bills of quantities on large projects, over 50% of the value of all building work in the United Kingdom is still let using lump-sum contracts with firm or approximate quantities. Most other procurement routes, such as design and build and management contracting in its various forms, also involve quantification of the work in some form or other by the main contractor, subcontractor or package contractor, and therefore the measurement process continues to be of importance.
Computerised and other alternative measurement systems have become more and more widely used. However, it is only by having a detailed understanding of the traditional method of setting down dimensions and framing descriptions that such systems can be fully understood and properly utilised. There continues to be development of 3D computer-aided design software that integrates with building information modelling, and the potential exists to generate quantities directly from the computer model. These sof