What Is Float In A Construction Schedule?

Float should be in every construction schedule. I get asked all the time, “Should we always have float? Should we not have float? Where do we put it? What kinds of things can I expect when I put it in there? And will the owner allow it? What do you do if the owner doesn’t allow it?” All these questions we’re going to answer in this blog post. 

What is Float in a Construction Schedule?

Float in a construction schedule is the amount that the activities, either together as a network or an independent activity, can move without affecting the overall schedule. This is basically the amount the schedule can move or push without actually affecting the end date. In my definition, it means avoiding stalking activities needlessly. So, it’s contingency. It’s a buffer, and I prefer the term buffer because we want to buffer impacts. Every schedule should have it.

When you take CPM (Critical Path Method) training the traditional way, CPM textbooks do talk about having scheduled contingency. The definition of the longest path is the longest path of activities, where if any of the activities were delayed, it would delay the entire project schedule. Often, owners will not allow float, contingency, or buffers at the end. They want you to back up your substantial completion date right to the end of that activity and have a critical path on the project. Owners use that critical path to avoid granting time or money for an actual impact on the project if it’s not on that critical path. As we’ve talked about in other posts, the critical path is not a great way to measure a construction schedule.

The Purpose & Importance of Float in a Construction Schedule

Float, when used correctly, is to absorb delays. Every construction project will have delays; every construction project will have problems. Throughout the course of the project, when you have that delay, or missing material procurement, or the rain day, you need the ability to move that construction schedule to the right, sustain a delay, and then use a buffer day, work contingency, or float. Every schedule should have it. There shouldn’t be any construction schedule in the entire world that doesn’t have float, contingency, or buffers because every project will have problems.

Of all the construction projects in the world, how many of them will go perfectly? How many will not even sustain one delay? How many will have every activity hit perfectly each and every time? Zero. If you said zero, then that’s how many schedules with no float you should have. Out of all the construction projects in the world, all have problems, delays, and issues that come up. So, all of them should have buffers, contingency, or float.

How to Add Float in a Construction Schedule

Risk Analysis

First, do a risk analysis. This is detailed in the book “How Big Things Get Done.” Look for your big risks, or “black swans,” and quantify days and dollars for them. Then ask yourself if your risks and days are covered with the float, contingency, or buffer at the end of the schedule.

Anchor Properly

Anchor your schedule by finding representative examples of similar projects done elsewhere. Put them into a database or your own Excel spreadsheet and calculate the average overrun for those projects in that region. Add that time into the actual schedule or make sure that, in addition to your risk days, it is included as buffers, float, or contingency.

Problems will happen. There’s no sense in having wishful thinking. Without float, when the end of the schedule starts to compress, you’ll start stacking trades and hurting people, which is why project teams start to crash land. Businesses wonder why projects seem fine in the beginning but end in a crash landing. It’s because schedulers, supers, and PMs dissolve logic at the end due to a lack of float, contingency, or buffers to absorb delays. Instead, they start stacking people, which only extends the project.

What to Do If the Owner Won’t Allow Float, Contingency, or Buffers

If the owner insists on using CPM without contingency and requires shared float between the owner and contractor, you are in trouble. First, analyze your risks and anchor. Your risks are the projected possible non-force majeure risks that could happen, and your anchor is the historical overrun for similar projects.

Show that data to the owner and ask for float, contingency, or buffers. If you can’t get it, do not resort to hiding buffers throughout the schedule. Craft a schedule that shows how critical some paths are and make sure you can track any delays accurately. If a time impact analysis can be submitted and approved, ensure the owner’s or tenant’s moving date is set beyond the risk profile.

Float should not be excluded from contracts, and owners should not penalize contractors for unavoidable delays. Using float, contingency, and buffers effectively will prevent stacking trades and overburdening projects with resources, which only extend project durations.

Important Reminders About Using Float in Construction Schedules

In the book “How Big Things Get Done,” misconceptions about pushing projects faster by overloading resources are debunked. This approach actually extends project durations. Owners who want fast projects should include buffers and avoid stacking and overburdening the project team.