Step 5 — Activity Durations

Step 5 Estimate activity durations

Activity durations should be realistic, achievable, and most likely with no padding for margin or risk.

Activity durations should be as short as possible to assist with the measurement of accomplished work, and durations in the short and medium term generally should not exceed the program updating period (i.e. 4 weeks). 

Long duration activities should be broken into shorter activities where practical. Exceptions include procurement of long lead time items and equipment.

Programs with a large ratio of activities with very short durations (i.e. 1 day or less) may be too detailed and will make it difficult to update and manage the program.

Methods for estimating activity durations include:

A first principles approach using measured quantities, productivity rates, resource and plant availability and a knowledge of construction methodologies is recommended when estimating activity durations when sufficient design information about the project is known.

Project team experts and activity owners within the project team should be consulted when estimating durations as they often have the best knowledge of how long certain activities will take in practice (e.g. the Design Manager will be able to give accurate estimates for how long each stage of design development and approvals are likely to take).

Assumptions related to duration estimates such as productivity rates, benchmark data and expert advice should be documented in the Basis of Schedule.

The number of resources available (labour and non-labour) can affect estimates of work and activity durations

Where possible significant resources should be assigned to the program to determine whether all required resources will be available when needed, to identify peak resource demands and to ensure resources can be managed effectively.

Any resources assigned to the program should be cross checked against resources allocated in the project budget.