Facing a project deadline can feel like a race against time for you. It’s a familiar scene: the clock is always ticking, your team is rushing.

The threat of being late is always there. This is where ‘Project Float’ comes in – It can help save your project from constant delays.

It’s tough to see your projects getting delayed. You watch the due date getting closer and think, “Can I make a difference here?”

The great news is: yes, you can.

Think of yourself as the leader who helps the team avoid delays and guides them to success. You’re moving from watching from the side to taking charge.

In my early days, I didn’t know how to use our schedule to avoid delays. I didn’t make the most of ‘Project Float’ to handle unexpected issues.

I couldn’t show them how to stay on track because I didn’t get how important the project float was. So, I didn’t get the recognition I hoped for. But, learning to use the project float and tracking them changed everything.

I’m here to guide you with 5 practical steps to master Project Float. You’ll gain the tools to track, manage, and apply it to your project. Ready to become the go-to expert your team relies on? Let’s get started.

1 – Understand What Influences Project Float

Ever started using a new tool and skipped the tutorial, only to get stuck later? That’s common with project planning, especially with project float. If you’re new, you might not get how float works.

Remember: if you put the wrong info into software, it will mess up your project’s float. Why? Project float’s tricky because lots of things can change it.

Beginners often rely too much on software and end up with errors. But, knowing what affects float can help you avoid those mistakes and guide your team better.

So, what affects project float? Here’s a simple explanation:

Activity Duration

Shifting gears in a car change its speed and control. Similarly, adjusting activity durations can change a project float. It affects how you can meet the deadline.

Imagine the scenario from our schedule below:

‘Brick Selection and Procurement’ in Float Path 2 has a 20-day float. How? Easy. Subtract Path 2’s duration (77 days) from Path 1’s (97 days).

This means you can push these activities back by up to 20 days without impacting the deadline.

But, there’s no room for delay in Float Path 1, our critical path (longest path), which takes 97 days. Any hold-up here delays the whole project.

Like Figure 3, If ‘Brick Selection’ and ‘Brick Procurement’ extend by 20 days, both paths become critical. It increases the risk of delay.

Schedule Network Diagram with Project Floats (20 Days on Float Path 2)

Figure 1

Gantt Chart Schedule with Project Float (20 Days on Float Path 2)

Figure 2

Key points?

Always review activities for a longer duration to see if they need all that time. And if you’re trying to speed up the project, think about shortening some activities.

This could help finish the project sooner, but make sure the team is on board and you have a plan for any risks.

Gantt Chart Schedule with Project Float (Zero Float on Float Path 2)

Figure 3

Activity Sequencing

Project float isn’t about how long tasks take. It’s also about the activity sequence. If you change the logic, the project float changes, too.

Take this scenario: The team decides to do ‘Doors and Window Work’ after ‘Roof Works’. This switch removes Float Path 3 and extends Float Path 1 from 97 to 107 days. Float Path 2 then becomes 87 days. So, the total float for Float Path 2 ends up being 20 days (107 days minus 87 days).

The key point?

The activity sequence really matters. Why? It affects your project float and duration.

To finish your project faster, consider changing the tasks’ sequence. Not just changing how long they take.

Figure 4

Activity Calendar

Project float isn’t just about duration or its sequence. It also depends on the activity calendar.

For instance, the ‘Engineering (90% Design)’ activity isn’t seen as critical. Why? It’s because of its successor—the board approval meeting’s calendar. It happens once a month.

The result? The critical path commences at the board meeting, not the project’s start date.

Critical Path Schedule Using Total Float Option

With the activity calendar being in the middle of the month, Critical Path doesn’t start from the start.

Figure 5

Figure 6

The takeaway?

Use the longest path, rather than focusing on activities with no float.

Here’s how you can do it:

Activate the ‘Longest Path’ option in P6’s schedule settings. This ensures you catch every critical task.

Critical Path Schedule Using Longest Path Option

Figure 7

Project Deadline

Imagine you’re planning a project, thinking you have four months to get everything done. This plan gives you some extra space to make changes if you need to.

But then, surprise! The deadline gets pushed up to 3.5 months. Suddenly, your float shrinks. You get negative float unless you rejig your schedule.

People handle deadlines differently. Some put constraint on a key milestone with a ‘Finish On or Before’ date, creating a deadline. Others set a deadline for the whole project at the project setting with ‘Must Finish By’ date.

I used to get confused about why I sometimes had more or less project floats than I thought. Then, I realised it was because the end date set in the project file.

The fix?

    • Always check if the schedule has already set a deadline in the project settings.
    • Then, update the deadline if required.

Figure 8

Setting a deadline reshapes your project’s float. It makes you rethink which activities are most urgent. When you hit delays, figuring out which tasks to prioritise can be tricky.

But, don’t worry; I’ve learned a few tricks to sort this out and will share more soon. So, stay tuned for the next updates.

Does Soft Constraint Matter?

You’ve probably heard this advice a lot:

  • Putting constraints on your project schedule isn’t the best move.
  • You should avoid ‘hard constraints’ like ‘Finish On’ or ‘Mandatory Finish.
  • It can make the schedule less reliable.

So, it’s common for you to think ‘softer constraints’ such as ‘Finish On or After’ or ‘Start On or After’ might be okay.

But, even these soft constraints can mess with how you calculate your project float.

I remember my time at a major mining company. We were evaluating schedules from another team. The recommendation? It was to use a dedicated calendar for shutdown instead of constraints.

The reason? Constraints mess with the accuracy of the Critical Path Method (CPM).

Take the scenarios below:

Scenario 1 – Critical Path with Constraints:

Imagine your project has constraints like ‘Start On or After.’

You’ll find the schedule doesn’t show the longest path because these constraints disrupt the CPM.

Figure 9

Scenario 2 – Critical Path without Constraints:

Now, think about removing those constraints.

Suddenly, the longest path becomes clear in float path 1. This shows that your project can display a proper critical path once you get rid of constraints.

Figure 10

The takeaway?

Relying too much on constraints can derail your project. Sticking to a simple calendar setup is a better option.

Now you know even softer constraints can change how your project floats. But did you know a little-known constraint called ‘As Late As Possible’? This also influences your project float.

Why As Late As Possible Screw Up Your Project Floats

During my time reviewing schedules for EPC contractors, I stumbled upon a common yet tricky constraint: ‘As Late As Possible’. I know it’s for a specific purpose. For example, the required on-site (ROS) date for equipment and material delivery.

But, my suggestion?

Avoid it unless absolutely necessary.

Here’s why: ‘As Late As Possible’ pushes activities to their latest start dates. The result? It makes them appear as critical with zero float. Why? Their end dates are tied to the next activity’s start.

Take brick procurement as an example. Without this constraint, it’s not critical and enjoys a 20-day float. When you apply ‘As Late As Possible’, it suddenly looks critical.

This shift can confuse your team. Activities that weren’t critical now seem critical. Muddling which activities need immediate focus.

The lesson here?

Use ‘As Late As Possible’ sparingly to keep your schedule clear and reliable.

Critical Path without Constraint

Figure 11

Critical Path with ‘As Late As Possible’ Constraint

Figure 12

Getting a handle on what influences your project float is vital. Reason? It allows you to fine-tune your schedule effectively. Yet, that’s merely the starting point.

The next step is to scrutinise the float values your scheduling tool provides. It’s not enough to take them at face value. You need to confirm that these numbers are realistic and truly reflect your project’s float. Are they realistic, or optimistic estimates?

Let’s dig in and verify the accuracy of your project’s float together.

2- Assess The Realistic of Project Float

Has your project team ever deviated from the schedule? It’s a common scenario.

Here’s what happens: I often get feedback from the team that the logic setup in this project is not right. The activity description is unclear.

Imagine a planner creates a schedule one way, but the team ends up doing things differently.

The planner discusses everything with the team. But the team doesn’t quite get the details in the schedule, especially with large projects.

This discrepancy leads to a gap between the plan and the team’s actual approach. Consequently, the project’s float in the schedule might not reflect reality.

I often face the question:

What’s the float for this task? In other words – the team ask if we have more time to complete this to reduce the team’s pressure. Must we complete it by next week to avoid impacting the deadline?

It’s hard to answer confidently if you’re not sure about your schedule’s real float.

The solution? Make sure your project’s float is accurately represented in your schedule.

1 – Validate Your Project’s Big Float

Wondering if those large floats in your schedule are correct? The first step is to verify them.

A large float can be helpful if they’re accurate – they help optimise resource usage and reduce stress. But if they’re not accurate, they can lead to missed opportunities, like extension of time (EOT) claims, and less accurate project completion forecasts.

Remember, project float depends a lot on activity sequencing. A large float could mean there’s a break in logic or incorrect task links.

Teams often think they have more time than they do. So, it’s critical to verify your project’s float is correct, as it can significantly impact your project’s success.

To make sure activity links are correct, especially in Primavera P6, follow the steps below.

How to Check Broken Relationships in P6

☑ Create a filter in Primavera P6 to trace the activities that do not have predecessor or Successor.

    • Select the Parameter “Any of the following.”
    • Then add the Parameter “Predecessors” is “equal” value “null” (leave it blank).
    • Do the same for Successors.

Figure 13

☑ Create a filter to find the uncompleted activity: find the activity that hasn’t been started or in progress.

Figure 14

☑ Finally, Select the “Activity Status Filter” and “Broken Logic Filter.”

Figure 15

2 – Review Negative Floats

Already checked for larger floats in your project? Next, look for any negative floats and figure out why they’re there.

Why check for negative floats?

    1. I always get feedback from the project manager and client that we need to come up with a recovery plan and don’t want to see negative float.
      • Because it suggests errors in the schedule or hints that your project might be having problems with schedule delays – (i.e. have a recovery plan to to tackle the delay or require approval for an extension of time).
    1. With negative floats, it’s tough to tell which tasks are most critical, making it hard to optimise your schedule for resources and dates.
    1. Don’t set your baseline schedule with negative floats around. Why? Because you can’t rely on the baseline total float to track your current schedule’s project float.
    1. You can’t use them for schedule risk analysis since they fail the quality check needed for such exercises.

Now you know negative float is bad for your project.

So, what’s behind negative floats? While there can be several reasons, these are common reasons:

      • Constraint Dates
      • External Links and Dates
      • Using Multiple Calendars with milestones

Figure 16

How to Check Negative Float Caused by the Constraints

In any project, you’re bound to run into constraints – it’s just part of the deal. But, it’s critical to know what constraints are in your schedule and which ones are causing negative float in your P6 schedule.

Here’s the thing: certain constraints can lead to negative float, especially when your scheduled dates stretch past the constraint dates. These are called hard constraints. Look out for these in your schedule:

    • Finish On
    • Finish On or Before
    • Start On or Before
    • Start On
    • Mandatory Finish
    • Mandatory Start

Try to avoid these constraints if you can. But if you must use one to show that your project is in trouble, go for constraints that start with ‘Finish On or Before’ or ‘Start On or Before’. These types still let you calculate your forecast date.

For example, when setting a project completion milestone, use ‘Finish On or Before’. If you look at the schedule below, you’ll see negative floats popping up because the project’s forecasted finish is later than the constraint date.

Figure 17

Also, If you’re taking over a schedule from someone else, just apply a simple filter for primary constraints and check out the constraint dates. This way, you can quickly see what constraints are already in the schedule.

Here’s how to find them easily:

    1. Finding the Columns (Primary Constraint and Date) – Not sure where these columns are? Just go to ‘View’, hit ‘Columns’.
    1. Use the Find Feature – Click on ‘Find’ to bring up a search box, and type in ‘Primary’ to get these columns.

Figure 18

    1. Filter for Primary Constraints and Date – Lastly, select ‘Start Constraint’ filter and ‘Finish Constraint’ filter in P6 to check activities with constraints.

Figure 19

How to Review Negative Float Caused by the External Links and Dates

Check Negative Float with External Dates – I’ve heard many times from my fellow planners saying – “I can’t get rid of negative float, but I didn’t have any constraint in the schedule.”

When you bring a project from another database, any missing links between the activities get replaced with ‘External Early Start’ and ‘External Late Finish’ dates. They act like constraints but don’t show up in the usual constraint date field in P6.

Wondering if your schedule has these external dates?

Here’s how to spot them easily:

  1. Add Columns – Pop in the ‘External Early Start’ and ‘External Late Finish’ columns to your schedule layout. Then, use a filter to check them out.
  1. Finding the Columns – Not sure where these columns are? Just go to ‘View’, hit ‘Columns’.
  1. Use the Find Feature – Click on ‘Find’ to bring up a search box, and type in ‘External’ to locate these specific columns.

Figure 20

  1. Filter for External Dates – Lastly, set up a filter in P6 to sift through activities that have these external dates.

Figure 21

Check Negative Float with External Links – If your project is linked to another project with constraints, it might cause negative float in your project. This negative float stays, even when you open your project alone.

To figure out which links are causing this, open all the projects linked to yours.

Figure 22

How to Validate Negative Float Caused by the Multiple Calendars

Got a negative float in your project and using several calendars? This could be why. I only faced this issue when I managed projects with multiple calendars.

Here’s what to do:

    • Remove any external dates and hard constraints first.
    • Then, hit F9 to refresh your schedule and see if the negative float is still there.

If you’ve still got negative floats, they might be due to milestones set on different calendars. Check this by adding Calendar and Activity Type columns in your activity view and look for milestones.

Figure 23

You’ve now checked the cause of negative floats in your project. To clear them, simply follow the steps in ‘Clearing Negative Project Floats in P6’.

After clearing the negative float, review your critical activities to ensure they align well with your team’s expectations.

3 – Review Your Critical Path

Just starting out in project management and wondering what the ‘critical path’ is all about?

The AACE’s RP 49R-06 describes the critical path as the longest sequence of tasks in your project that you need to finish. These activities are critical because they determine the project’s shortest completion time.

Similarly, PMI’s PMBOK guide’s 7th edition tells us the Critical Path is the longest sequence of activities in a project. It’s this path that sets the limit for how quickly you can complete the project.

Consider a scenario from the project below:

The project has 4 float paths; out of these, only the longest one really defines when your project will be completed. That’s your target – always focus on this longest path to hit your deadline.

Figure 24

Remember, lots of things influence project float, which in turn defines these critical paths – sequences of activities with zero total float.

One major factor? How you link these activities. If activity logics are wrong, you’ll see unrealistic delays or incorrect critical paths popping up. So, double-check whether the critical path shown by the software actually makes sense for your team.

How to do that? Start with analysing project float. Ready to tackle critical paths in P6? Let’s dive in.

How to Review Critical Paths Using Total Float in P6

STEP 1 – Set the schedule option to ‘Total Float’.

By default, P6 has already set the schedule options to total float. However, I recommend you check the options to make sure the recommended options are selected. So follow the steps below:

☑ Go to ‘Tools’ , then ‘Schedule’ or Press ‘F9’ to get the schedule options screen.

Figure 25

☑ Select the schedule options to define the critical activities as “Total Float less than or equal to’. If you want to be conservative, you can make the critical activities for the activities with total float less than 5 days or whatever days or hours you want to choose.

And, make sure to select the ‘Mark open-ended activities critical’ and ‘Use Expected Finish Date’.

Figure 26

☑ Finally, filter the critical path activities.

Figure 27

STEP 2 – Sort the activities with start date or finish date, and check if they form like a ladder shape from the beginning of the project to the end.


If the critical path doesn’t clearly show activities from the start to the end of the project, it’s time to adjust the logic, constraints or calendar.

We’ll dive into the specifics on how to do this in the next section.

Figure 28

STEP 3 – Keep going even If you find the critical path activities from the beginning to the end.

Talk to your team about whether the critical path from P6 matches what they expect. Print out the schedule that shows only the critical activities, and another one with all activities, including the columns for predecessors and successors. This gives everyone the information they need to review the schedule in detail.

Here’s what I usually do:

Send out the PDFs first so the team has time to review the schedule. Then, we meet to go over the P6 logic together in real-time.

How to Review Critical Activities Using Longest Float Path in P6

For bigger and more complex projects, having the option to check the longest path is a great way to check the critical path activities show as expected.


Using the longest path option to check the critical path activities you will uncover the activities which are not the critical path using total float option.

To check the longest path activities follow the steps below.

STEP 1 – Set the schedule option to ‘Longest Path’

☑ Go to ‘Tools’ , then ‘Schedule’ or Press ‘F9’ to get the schedule options screen.

☑ Select the schedule options to define the critical activities as “Longest Path’.

And, make sure to select the ‘Mark open-ended activities critical’ and ‘Use Expected Finish Date’.

Figure 29

STEP 2 – Change the Advanced Scheduling Options Setting

To get P6 to show you the most critical paths in your project schedule, follow these steps:

    1. Go to Advanced Settings: First, go to the Schedule Options. Once there, you’ll find a tab labelled ‘Advanced’. Click on this tab.
    2. Turn on Multiple Float Paths: Find the option ‘Calculate multiple float paths’ and select it. Also, choose ‘Total Float’. This tells P6 to look at various paths in your project, not just the longest one.
    3. Pick the Final Activity for the Longest Path: If you want to see the path to the end of your project, select the last activity, like ‘Project Completion’. P6 will then show the longest path of the project.
    4. Select a Milestone for Specific Path Focus: To focus on a critical milestone before the project ends, like ‘Ready for shutdown’, choose that activity. P6 will highlight the longest path to reach this milestone, showing you critical activities for that deadline. Use this technique when you want to concentrate on critical tasks to meet an interim deadline.
    5. Set the Number of Paths to Display: You can choose how many different paths P6 shows you. Just enter a number, like 10, and P6 will display up to that many paths. Leave the ‘Display multiple float paths ending with activity’ box empty if you use this setting.

Figure 30

STEP 3 Organise the Float Path Layout

A well-organized view is key to making sense of your data:

Go to Views > Group and Sort by and group activities by “Float Path”. Ensure that titles and names/descriptions are visible for easy reference.

1) Under Group By column, choose “Float Path”.

2) Under Show: select tick “Title” and “Name/Description”.

Figure 31

STEP 4 – Schedule (Press F9) to See the Result

Alright, you’ve made it through the steps, so here’s the fun part: Press F9 and watch the magic happen: float paths light up your screen. Go ahead and save that layout once it pops up.

You’ll see float paths as you’ve defined. But, a heads-up: skipped the baseline setup? Then you’ll miss out on key details like the baseline total float, and baseline finish variances.

Figure 32

4 – Ask For More (Get to the Heart of Your Schedule)

Have you ever sent off your schedule to question if it really captures the critical path accurately? But checking the schedule for Critical Path is just the start.


Steven Bartlett once said, “Ignoring the small stuff leads to big problems. Success is all about paying attention to the little details.”

So, how do you ensure your project schedule is right? Here’s what you need to know:

    • Ask, Then Ask Again: Don’t settle after the first round of questions. If you’re wondering about how activities are sequenced or their durations, keep the inquiries coming. It’s the only way to uncover and correct errors that could disrupt the project float.

I’ve been there, asking my team things like, “For our estimate, should we only consider vendor quotes, or do we wait for client approval for evaluation first?” Each project is unique, and it’s these detailed questions that clarify our plan and ensure our project float is real.

    • Know Your Project Inside and Out: Understanding why and how the activity is scheduled in your project isn’t just extra work. It’s essential for identifying and fixing schedule issues to make sure your project’s floats are real.

Remember, it’s the little questions and the deep understanding that keep your project float accurate.

Your Next Step in Project Planning

Feeling overlooked and doubting your project float numbers? It’s more common than you think. You’re putting in the effort, but it feels like nobody notices the hard work behind those numbers on the screen. Frustrating right?

But here’s the real deal: Doubting doesn’t mean you’re failing. It means you’re ready to level up. This isn’t just about numbers; it’s about you becoming the project adviser who sees beyond the software.

You’ve learned today that it’s not enough to just accept what the software says. You’ve got to dig deeper, question it, and make sure those floats are real. This makes you more than a planner (planning engineer); it makes you a critical part of your project’s success.

And guess what? We’re not done yet. In our next update, I’ll show you how to fine-tune your skills even more. You’ll learn how to make sure your project float is not just a number, but a realistic one that you can use to tackle project deadline.

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