Meeting Project Schedule Constraints: Schedule Compression Techniques

Well-managed projects have a precisely detailed schedule model. When a client looks at this model, they should see the project's estimated date of completion, how long the entire project will take, the individual activities that comprise the project, which activities come first, and when such activities will start and finish. A closer inspection should also reveal the relationships among specific activities, schedule constraints, and resource requirements for individual activities (and the entire project).

A project manager or project management consultant develops and continually refers to a project's schedule model for monitoring and control. When delays in individual activities can significantly set the project back, they may implement schedule compression techniques.

What Is Schedule Compression?

HOW TO BUILD A CONSTRUCTION SCHEDULE WITH MS PROJECT

Schedule compression is shortening or accelerating the project duration (or the duration of individual activities). It becomes necessary when a project manager cannot change the project scope, but their float analysis indicates the project will get delayed.

Negative Float

Float is the amount of time (or number of days) a specific project activity can be delayed without affecting other subsequent activities' start and end dates. 

Tasks on the critical path – i.e., the activities whose cumulative durations determine a project's length and estimated completion date – have zero float. In other words, they cannot be delayed without delaying the project.

When a task on the critical path has negative float, it means that activity will start later than its estimated late start date. Thus, a negative total float indicates the project will finish later than the estimated late finish date – i.e., delayed project completion.

When there's negative float, a project manager can try to regain lost time through schedule compression. Schedule compression is also performed for the following reasons:

• To work around time-sensitive resource constraints

• To meet imposed due dates

• To complete the project faster

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Also read in Project Management:

The importance of the procurement and procurement selection process in the construction industry

NEC4: Financial Protection Plan explained in relation to the contracting organisation appointed

Project Management tools: Line of Balance (LOB), Cost Optimisation, and PERT

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Schedule Compression Techniques

There are two schedule compression techniques project management services providers use to accelerate project timelines. They are crashing and fast-tracking.

1. Crashing

Crashing involves shortening activity or project duration by adding resources. It works only on activities where adding resources will speed up task completion.

Crashing Example

If two demolition hammers mean four days of work stripping concrete off-road surfaces, the project manager can double the number of demolition hammers to cut the number of days by half (i.e., two days). Moreover, if there are no practical constraints to doing so, the project manager can even increase the number of jackhammers to eight and complete the task in just one day.

Note: Increasing the number of jackhammers naturally leads to an increase in demolition hammer operators.

How to Crash Projects

The following are common crashing strategies:

• Workforce expansion: If a two-day task initially planned with two workers is behind schedule by two days, adding two workers may help ensure timely task completion.

• Overtime: Paying employees or staff to work overtime is the easiest crashing measure to implement. The longer work hours can help make up for any time lost. Just note that employees may be less productive outside of official working hours. Overtime is, thus, usually a short-term solution, the frequent use of which can lead to adverse consequences (e.g., burnout, inefficiency).

• Hiring specialists and experts: Bringing in experts can significantly shorten timelines.

• Renting additional equipment: The jackhammers above are an example of this strategy.

• Outsourcing: Hiring external vendors to handle specific project components can speed up tasks that the internal team may not have the capacity to complete or finish quickly.

To reiterate, crashing is adding more resources to a project. Resources can be people, work hours, expertise, and equipment, and the goal of adding these resources is to shorten the amount of time an activity will take.

2. Fast-Tracking

Fast-tracking is the concurrent or overlapping execution of activities or tasks normally done in sequence. By letting tasks overlap instead of following a strictly sequential progression, a project manager can save time and ensure they meet specific activity due dates or complete the project on time.

Fast-Tracking Example

A contractor typically starts a warehouse construction project by building the base or foundation. Once that's completed, the contractor erects the steel frame, which typically has the following components:

• Steel columns

• Roof beams

• Roof trusses

• Floor beams

• Braces

• Tie rods

• Purlins

• Wall beams

• Stays

Once the frame is complete, the contractor lays the roof and walls. Thermal insulation may be added as needed. Once the building is finished, the wiring, plumbing, ventilation, and finishing work can proceed.

If the project manager must cut the timeline short, they can start dependent and subsequent tasks while their preceding activities are still ongoing. For instance, the steel frame may be prefabricated while the foundation is laid out. Likewise, roof construction may start even though the steel frame is yet to be completed.

Just note that fast-tracking is risky. Without careful planning and risk management, fast-tracking can lead to redos and, thus, an even longer setback on schedule.

Accelerating Project Timelines

Project managers may sometimes need to compress schedules to complete significant milestones and meet deadlines. To this end, they can crash the project, fast-track it, or even do both concurrently or one at a time, depending on specific project circumstances, the nature of individual activities and schedule compression objectives.