Undefined provisional sum
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’.
Undefined provisional sums are less well described as they refer to work which is not completely designed. As such, the contractor cannot be expected to make allowance for them in their programming, planning and pricing preliminaries. This means the contractor may be entitled to an extension of time and/or additional payments when the actual works are undertaken.
An example of an undefined provisional sum might be work required below an existing structure, where the ground conditions, and so the extent of work required, cannot be determined until the structure is demolished and the ground opened up.
With undefined provisional sums, the client typically bears the price and scheduling risks.
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.
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