Schedule Delays in Construction Projects: 7 Key Factors

project delay site

Schedule delays are an ever-present challenge in construction projects, causing frustration, financial strain, and even legal disputes. Understanding the root causes of these delays is crucial for project managers, stakeholders, and anyone involved in the construction industry. In this post, we’ll delve into the key factors behind schedule delays.

Poor Planning and Scheduling

If the project scope is inaccurately reflected in the schedule and the method statement remains undefined, our schedule is likely to experience a delay. This is due to insufficient information and incorrect sequencing of tasks. According to a report by McKinsey & Company, up to 80% of projects experience schedule delays due to poor planning.

Design Changes and Rework

Design changes and rework can significantly disrupt a construction project’s schedule by extending timelines, necessitating schedule revisions, reallocating resources, and complicating task dependencies. This often leads to delays in critical milestones and impacts overall project deliverables. Changes can occur due to client requests, regulatory requirements, or unforeseen site conditions. Design changes often necessitate rework, causing delays. The Construction Industry Institute (CII) estimates that design changes account for 7-10% of total project costs and contribute to schedule delays in 35-40% of projects.

Resource Constraints Related Schedule Delays

Inadequate allocation of resources, such as labor, materials, and equipment, can lead to schedule delays. This may occur due to budget constraints, supply chain disruptions, lack of supervision or unrealistic resource estimates. Research by the International Journal of Project Management indicates that resource constraints are a leading cause of delays in construction projects, impacting approximately 30% of projects worldwide.

forensic schedule delay analysis

Weather and Environmental Factors

Construction projects are susceptible to weather and environmental conditions that can impede progress and extend timelines. Extreme weather events, such as hurricanes, floods, and snowstorms, can halt work entirely or limit productivity on-site. A loss in productivity caused by these factors will lead to delays in our schedule. A study published in the Journal of Construction Engineering and Management found that weather-related delays account for an average of 3-5% of total project duration.

Schedule Delays Due to Labor Shortages and Skills Gap

The construction industry faces challenges related to labor shortages and a widening skills gap. As experienced workers retire and fewer individuals enter the construction workforce, projects may struggle to find skilled labor, leading to schedule delays. The Associated General Contractors of America (AGC) reports that 81% of construction firms are experiencing difficulty filling skilled positions. Labor shortages and skills gaps  are contributing significantly to project delays across the industry.

Unforeseen Site Conditions

Construction sites are susceptible to unexpected events. During construction, instances may occur where soil reports prove inaccurate and chosen work methodologies are unsuitable for the site. Moreover, archaeological artifacts are sometimes discovered, or underground utilities are encountered. All of which can lead to expensive modifications and delays in the project schedule. A study published in the Journal of Construction Engineering and Management found that unforeseen site conditions contribute to schedule delays in approximately 20-25% of projects.

Permitting and Regulatory Schedule Delays

Navigating the complex landscape of permits and regulations can often result in delays for construction projects. Delays in obtaining permits, complying with environmental regulations, or addressing zoning requirements can prolong project timelines and increase costs. The National Association of Home Builders (NAHB) estimates that regulatory requirements add an average of 24.3% to the cost of a new single-family home. Permit delays were reported as being a significant contributing factor.


Schedule delays in construction projects can stem from a variety of factors, ranging from poor planning and design changes to external factors like weather and regulatory delays. By understanding these key causes and their implications, project stakeholders can take proactive measures to mitigate risks. This enhances project management practices and improves overall project outcomes. By prioritizing thorough planning, effective communication, and proactive risk management, construction professionals can navigate the complexities of schedule delays  to deliver projects successfully, on time, and within budget. However, schedule delays are unavoidable; learning how to navigate delay claims is an essential arrow in any project scheduler or manager quiver.

In our Forensic Schedule Delay Analysis live course, you will be introduced to the concepts, processes and techniques that are key to understanding the root causes of project schedule delays. Whether you’re confused by what schedule delay analysis is for, or you just need to fill in your knowledge gaps, Tyler Konter will share everything you need to know about Forensic Delay Analysis for Construction projects, from definitions to expert techniques and processes.

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delay detective

Faraz, a Primavera P6 expert and trainer at Plan Academy Inc., brings extensive experience as an engineer and educator. With a background in civil engineering and years of industry experience in construction, manufacturing, and MEP, he plays a crucial role at Plan Academy in developing and delivering up-to-date educational content. His goal is to empower students and professionals with the skills and knowledge needed to succeed in Project Planning & Control.