Last edited 24 Feb 2021

Negative float

The concept of float (or 'slack') is used to describe the amount of time that an event or activity can be delayed without delaying the overall completion of the works. Float is calculated by subtracting the time necessary to perform a task from the time available to perform it.

The concept of float (or 'slack') is used to describe the amount of time that an event or activity can be delayed without delaying the overall completion of the works. Float is calculated by subtracting the time necessary to perform a task from the time available to perform it.

Float is generally considered to be positive rather than negative unless stated otherwise.

The CIOB Planning Protocol 2021 (CIOB PP21), a technical information sheet published by the Chartered Institute of Building (CIOB) in February 2021, defines negative float as: ‘Where the float present is less than zero, denoting that intrinsic delay is present.’

Negative total float refers to the time by which the duration of an activity or path has to be reduced in order to permit a limiting imposed date to be achieved. Negative float only occurs when an activity on the critical path is behind programme. It is a programming concept, the manifestation of which is delay. Ref The Society of Construction Law Delay and Disruption Protocol, 2nd edition, published in February 2017 by the Society of Construction Law (UK).

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