Are You Making These 12 Construction Scheduling Mistakes?

Category: Construction | By ClockShark | 3 minute read | Updated Jun 1, 2019
Are You Making These 12 Construction Scheduling Mistakes?

I find construction scheduling invaluable on all of my projects. For small projects, they could be simple hand-drawn bar charts and for large projects, they could consist of thousands of linked tasks created using specialist software such as Primavera, Microsoft Project, Candy or similar.

Schedules are important because

  1. They inform the construction team of what tasks they should be working on and when.
  2. They advise the customer when they should provide construction information and grant access to the contractor.
  3. They are invaluable for calculating the extension of time claims.
  4. The progress of the project can be measured.
  5. A resourced schedule enables the contractor to plan when resources are needed and how many of each resource is required.
  6. Material deliveries can be arranged so they’re delivered before they’re needed.
  7. Subcontractor’s work can be planned so they arrive when they’re needed and complete their work on time.
  8. They can be used to plan cash flow.
  9. Knowing the project duration the contractor can calculate their overhead costs for the project.
  10. A properly planned schedule will avoid clashes or hold-ups on the project caused when the preceding necessary tasks haven’t been completed.

However many construction scheduling is poorly prepared and has numerous errors that can mislead both the contractor and the customer. In fact, a poorly prepared construction schedule, or a schedule with errors, can be more dangerous than having no schedule at all.

Common scheduling mistakes

Some of the more common errors include:

1. Making the schedule fit

Making the schedule fit the customer’s dates even if they aren’t achievable. Usually in the request for a price the customer provides the start and end dates for the project. Sometimes contractors simply accept these dates assuming they can complete the project in the time provided, when in fact it’s not possible. On other occasions, the contractor ‘squeezes’ their schedule to make their construction time fit within the client’s dates, even when they know it’s impossible to meet these dates. This can be dangerous for many reasons:

    • Inevitably the contractor cannot finish the project in the allotted time and they not only face the prospect of paying liquidated damages but their reputation is damaged.
    • The contractor remains on the project longer than allowed in their price resulting in them losing money.
    • The contractor’s team may become demoralized knowing they can never meet the required dates, knowing no matter how hard they work the client won’t be satisfied with their performance, and in fact, even their senior management will blame them for delivering the project late.

Contractors shouldn’t commit to dates they cannot achieve. They could either submit an alternative achievable schedule that doesn’t satisfy the client’s dates, or not price the project, or discuss with the customer alternate methods or strategies to enable the customer to get access to parts of the project they require on their required dates.

2. Schedule without methodology

Formulating the schedule without considering the construction methodology. Frequently I see schedules that were drawn up by a planner with no input from the construction team.

In fact, some of these schedules don’t even consider the construction methodology the construction team is using. This is obviously pointless because the project progress is often difficult to measure since the tasks are in a different order, or possibly don’t even appear on the schedule.

3. Weather conditions

Failing to allow for the normal expected weather conditions. Contractors frequently complain of weather delays. But often the weather experienced is normal for that region at that time of the year. Yes, on occasion there are abnormal weather events (something that seems to be occurring more often) which cannot be expected.

However, contractors should allow for normal weather interruptions which could include rain, winds, snow and extreme temperatures which could disrupt the project or reduce productivity.

4. Impact of adjacent structures

Scheduling individual structures without considering the impact of adjacent structures, or the impact they’ll have on adjacent structures. Many structures on a project are connected in some way. Deeper structures may have to be completed (or certainly brought to the underside) before the neighboring structure can begin.

Structures can impact access to the neighboring structures. When preparing a schedule it’s essential to consider the impact of adjacent structures and utility lines on other structures.

5. Forgetting the project constraints

This should be simple, yet sometimes contractors don’t allow for customer imposed restrictions which could include restrictions on working times and accommodating other contractors or the customers' own activities. Sometimes even statutory holidays, when work can’t be done, are forgotten.

6. Material procurement

Allowing inadequate time for material procurement. Some materials require lengthy procurement periods to allow for design, design approval, preparing drawings, drawing approvals, fabrication, and shipping.

7. Ignoring inspections and testing

Waiting for test results can delay follow-on work. Often the client has to witness completed work or test results before the next activity can begin.

8. Not allowing for commissioning

In some facilities, commissioning can take several weeks. This commissioning may include tying into existing infrastructure and utilities. It could include passing tests witnessed by the customer or the various authorities, closing out major snags, completing documentation and obtaining permits.

9. Allowance

Failing to make allowance for local conditions and productivity. Productivity can vary hugely between countries, and although wage rates may be lower in some places you may need four times as many people to complete the same task at the same time. But productivity also depends on the customer and their operations.

Working in an oil and gas processing facility may require far more rigorous quality and safety standards than working in the city. Some facilities have stringent security which can make it difficult to get people, equipment, and materials onto the project. Projects working in busy traffic can result in slower progress. But even not being able to find people with the required skills can impact productivity and hamper progress.

10. Single area

The schedule allows, or demands, too many trades having to work in a single area at the same time. Only a finite number of workers and different trades can work in an area at the same time.

Fitting more people and activities into a small area doesn’t make the work go quicker – in fact, it often results in the work going slower as workers work on top of each other or have to stand-down waiting for others to complete their work. Freshly completed work may be damaged by the follow on trades because the materials haven’t dried or cured resulting in the work having to be redone.

11. Schedule update

Not updating the schedule correctly or failing to take action when slippage occurs on the project. At times the construction schedule isn’t updated correctly and progress isn’t recorded correctly giving the contractor and the customer misleading information.

On occasion when slippage is detected the contractor ignores the information and doesn’t take corrective action, or takes the wrong actions which don’t help. It is essential slippage on the schedule is detected early and the correct actions are implemented to catch up the lost time.

12. Not conveying the schedule to the team in the field

All too often the contractor has a schedule which is kept in the office, but those in the field aren’t aware of what tasks need to be completed and by when. Sometimes the contractor simply hands the complete schedule, of thousands of activities, to the supervisors and expects them to find those tasks which are relevant to their section of works.

It’s essential that those in the field know what tasks have to be completed when they must be completed and even the reasons why some tasks must be done first. Providing the schedule in a pictorial form, showing just the activities relevant to that area which must be completed in the next three weeks, can be useful as this can be pinned to the shed wall where it can be viewed by all workers from that section.

The team must be told when progress is slipping. Importantly though, they must have the correct resources and must receive their materials in good time so that they can deliver the project on schedule.


Preparing the best workable schedule is an art, a science and one that needs expertise and experience. The schedule needs to reflect how the construction team will build the facility, the realities of the construction site, the available resources and skills, the local conditions and the contractual requirements.

Committing to a schedule that is impossible will cause damage to both the contractor and the customer. Following a schedule with flawed logic will invariably result in a delayed project. Ignoring the schedule or not conveying the contents of the schedule to those in the field defeats the purpose of preparing the schedule.

Schedules are useful to contractors and customers and shouldn’t be viewed as just a contractual requirement or another document for the customer to ‘whip’ the contractor.

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