Last edited 10 Oct 2018

Common mistakes in bill of quantities

A bill of quantities (sometimes referred to as 'BoQ' or 'BQ') is a document prepared by a cost consultant (often a quantity surveyor) that provides project-specific measured quantities of the items identified by the drawings and specifications in the tender documentation for construction works.

It is very important that bills of quantities are prepared according to a standard, widely recognised methodology. This helps avoid any ambiguities or misunderstandings and so helps avoid disputes arising through different interpretations of what has been priced.

However, there are some common mistakes that can be made in the bill of quantities. These include:

  • Inaccurate measurement of quantities.
  • The inclusion of irrelevant preliminary items (this can be due to using preliminary items from a previous project which, although it may be similar, contains differences in scope).
  • Insufficient information given in the descriptions.
  • Omissions and discrepancies between the BoQ and the drawings or specifications (perhaps due to out-of-date or inaccurate information being used).
  • Omissions or double-counting of items (this can be due to more than one quantity surveyor working on the same bill).
  • Omission of temporary works items.

There can also be errors made in the pricing, such as:

  • Incorrect understanding of the work method.
  • Past performance used to assume future productivity.
  • Inexperience of the estimator.
  • Ignoring the relationship between items of work.
  • Changes that are made late in the process.
  • Inaccurate assumptions regarding items in the BoQ.
  • Arithmetic errors.
  • Differences in currencies not considered.

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