Planning techniques

Software

Computer software for planning applications is generally based on the technique referred to as critical path analysis. Each brand of software has its own particular features: some have better graphics, while others offer more powerful processing, customisation and sorting capabilities. Most of the software can exchange data with other planning packages, as well as with standard spreadsheet and database applications.

Critical path analysis calculates the activity timings in a relatively simplistic manner with the process consisting of a basic addition and subtraction exercise. If the data input is flawed the computer cannot and will not rectify those flaws. Proficient planning should be based on knowledge and experience of the construction process rather than the ability to manipulate the software.

The key purpose and function of planning is to inform and communicate the plan to the project team and to provide a means of monitoring progress. Planning software is a valuable and powerful tool enabling an easy way to exchange data and to produce sub-programmes and reports. Software will generally enable:

• activities to be coded or categorised, for example by work area or trade, allowing filters to be applied to create a programme sorted to show a discrete selection of activities, such as all of the services activities or all of the activities relating to the first floor;
• groups of activities can be summarised to produce 'high-level' strategic programmes;
• histograms and 'S' curves can be produced, which enables resource levels and expenditure to be illustrated graphically; and
• programmes can be updated and amended promptly, allowing 'real-time' progress reporting.

Computers have revolutionised construction programming and planning but planning analysis still involves understanding the project scope, considering potential alternatives, breaking down the works into the relevant activities, defining the likely activity durations and identifying the relationships between the considered activities. It is not a matter of producing programmes that are correct; it is more about considering what is reasonable and achievable.

Bar charts

Bar charts and Gantt charts are extensively used in the construction industry. They are simple, well recognised, accepted and readily understood and the format very effectively displays and communicates the necessary information. Programming software, although often based on critical path analysis, will display the results in a bar chart format..

A bar chart does not have to be produced by a specialist programmer. Construction managers can produce their own programmes to communicate their plans to the various subcontractors, procurement programmes can be developed, and simple summary programmes can be produced to report overall project status to senior management or clients.

This ease of production can however be considered a disadvantage as it may mean that activities may be scheduled with insufficient thought or consideration of duration. If too many different updated bar charts are issued on a project, some of which prove to be flawed and unrealistic, it will eventually lead to a disregard for them. It is wise to limit the production and update process.

Another drawback is that they do not react dynamically to change. Therefore, there are limitations in recording site progress, assessing the overall project progress status and identifying any causes of project delay.

Linked bar charts

Some of the issues with bar charts can be eased by indicating logical dependencies between the activity bars in a 'linked bar chart'. These dependencies help to reinforce the planned intent and will force the programme author to consider the activity relationships and durations a little more carefully.

A linked bar chart can be scheduled in much the same way as a critical path analysis. It will also graphically show the activity 'float' as well as those activities that are critical. When a bar chart is linked in this way it can be re-scheduled utilising the computer software, following the input of progress data. Unlike the simple bar chart, the linked bar chart will react dynamically, adjusting the timing of the remaining work activity bars and demonstrating any variation to the overall date for completion.

Most software will only represent logical links between the activity bars graphically; there is no separate analysis to show how links have been made, as there is with critical path analysis software applications. Links shown graphically are likely to be difficult to follow on all but the most simple programme and so, even with the data in an electronic format, it may prove difficult to interrogate the logic links applied in order to verify it.