In this article, we take a look at the subject of ‘float’ in construction project scheduling. On the most basic level, construction projects are intricate networks of interconnected tasks. When one task experiences delays, it can create a domino effect, disrupting the entire project timeline.

This is where the concept of float becomes invaluable. Let’s try and take a look at how it works…

What Exactly is Float?

It represents the amount of time a specific task can be delayed without jeopardising the overall project completion deadline.

Consider the construction project programme as a chain. Each task is a link, and the critical path (used by project managers to schedule activities) is the tightest sequence of links that determines the project’s finish date. Sticking with the metaphor, float is the “slack” in the chain for non-critical links. It provides a buffer or flexibility within the schedule.

Are There Different Types of Float?

Here’s where it begins to get a little complex — there are different types, depending on context. But, for most scenarios, there are two key float concepts to understand:

1. Total Float: (TF) is the time a task can be delayed without delaying the project’s completion date. For example, if a task is scheduled to start on Monday and finish on Friday, but the next dependent task does not start until the following Tuesday, the task has a total float of one day.
2. Free Float: (FF) measures how much delay the current task can tolerate, without affecting the start of the next sequential task. It’s more localised than total float and applies to individual tasks rather than the project in its entirety.

Why is it Important?

While it might sound like technical jargon, float is a very powerful tool that can help teams learn more about their work. It can help improve the productivity of projects. Moreover, it’s crucial for maintaining flexibility in project programmes. This in turn helps project managers allocate resources more effectively, handle unexpected delays, and prioritise tasks to keep a project on track.

As an example, imagine a project which – among a myriad of things – contains two near-term tasks:

1. Paint walls
2. Install light fixture

Painting has two days total float, whilst the light installation has none, as it is on the critical path. But with limited resources a delay occurs. In this scenario, by prioritising lighting, the the overall project timeline remains on-time. The painting task can be rescheduled by up to two days later without affecting the critical path and completion date.

This is where prioritising activities comes into play. Rescheduling activities allows for the most efficient use of float. Importantly, this will preserve the expected completion date.

As you can begin to see, understanding the concept supports better communication between stakeholders and avoids unnecessary panic over tasks that do not immediately impact deadlines.

The Key to Delivering Projects On Time and Within Budget.

Without a thorough understanding of float, you will struggle to successfully manage projects in the construction industry and will likely be confronted with delays. By incorporating it into project schedules, project managers can enhance efficiency, limit risks, and ultimately deliver projects on time and within budget. For more detail on the ‘ownership’ of float take a look at this article.

This article was written by Paul Woodley BSc, LLB, MCIArb.

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