Last edited 30 Nov 2018

Defined provisional sum

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A provisional sum is an allowance (or best guess), usually estimated by a cost consultant, that is inserted into tender documents for a specific element of the works that is not yet defined in enough detail for tenderers to accurately price.

A provisional sum can be categorised as ‘defined’ or ‘undefined’.

Defined provisional sums are those which have been described in sufficient detail that the contractor is expected to have made allowance for them in their programming, planning and pricing preliminaries. The work may not have been completely designed but the following information may be known:

  • The nature and construction of the work.
  • How the works may impact on the existing building or surroundings.
  • The quantities that indicate the scope and extent of the work.
  • Any specific limitations.

An example might be where a defined amount of brickwork is required, but the exact design has not be finalised and so the price cannot be accurately determined. Or the cost of installing a timber frame where the specific type of timber has not yet been specified and so its price is not known.

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