Best Practices for Preventing Out-of-sequence Construction Activities and Minimizing their Impacts

RT-334 Topic Summary
RT 334


RT-334 defined out-of-sequence work (OOS) as an activity or series of activities that are not performed according to a planned logical productive sequence. Despite the seriousness of the challenges that OOS imposes on the construction industry, the existing body of literature lacks direct solutions for how to handle OOS. As such, the RT-334 research is the first of its kind, as it investigates the causes, warning signs, and impacts of OOS. It also provides proven concepts for preventing OOS and minimizing its negative impacts.

Through performing an expert-based study (surveying 88 experts) and a project-based study (tracking 42 projects), as well as integrating the collective academic and professional wisdom of the team, RT-334 was successfully able to accomplish the following tasks:

  1. Identify 88 causes of OOS, spanning 11 categories, and rank them with respect to likelihood of occurrence, relative impact, and risk rating.
  2. Identify 56 warning signs of OOS, spanning 11 categories, and rank them with respect to their correlation with the occurrence of OOS.
  3. Identify and quantify the significant impacts of OOS, spanning five performance areas.
  4. Detail 164 effective preemptive and responsive actions, spanning 21 concepts, to prevent OOS and mitigate its negative impacts.
  5. Evaluate the effectiveness of frequently used mitigation strategies for minimizing OOS.
  6. Develop a user-friendly computer-based tool “OOS Decision Support System” that aids practitioners in evaluating the OOS risk of their projects (using OOS gauge) as well as minimizing it through tailoring the research findings to best suit them.

Figure 1. Key Takeaways of RT-334


Related Academic Publications (not published by CII)

Abotaleb, Ibrahim S., and El-adaway, Islam H. (2018) “First Attempt Toward a Holistic Understanding of the Interdependent Rippled Impacts Associated with Out-of-Sequence Work in Construction Projects: System Dynamics Modeling Approach.” Journal of Construction Engineering and Management (144)9. This paper received the 2020 ASCE Thomas Fitch Rowland Award.

Abotaleb, Ibrahim S.; El-adaway, Islam H.; Ibrahim, Michael W.; Hanna, Awad S.; and Russell, Jeffrey S. (2019) “Causes, Early Warning Signs, and Impacts of Out-of-Sequence Construction: Expert-Based Survey Analysis.” Journal of Management in Engineering (35)6.


Key Findings and Implementation Tools

1 : Causes and Warning Signs of Out-of-sequence Work (OOS)

RT-334 identified 88 causes and 56 warning signs of OOS, spanning 11 categories, as shown in Figure 2.

Figure 2. Numbers of Identified OOS Cause and Warning Signs Spanning the Studied Categories

Through its expert-based study, RT-334 established the likelihood of occurrence and relative impact of these 88 OOS causes, and used this information to calculate corresponding risk ratings for each cause. These risk ratings were then used to categorize the causes into six risk tiers, with risk-tier 1 being the riskiest and risk-tier 6 being least risky. Following are the first two risk-tiers, including the top 10 causes of OOS:

Risk-tier 1: Category:
       1. Late design deliverables Engineering
  2. Changes in design Engineering
  3. Expedited schedule to meet owner’s requirements Execution

Risk-tier 2:
  4. Schedule pressure Execution
  5. Late vendor information Engineering
  6. Late delivery from vendors Materials management
  7. Unrealistic activities duration Planning
  8. Poor communication between project parties Project team
  9. Late scope changes requiring different equipment/processes Change management
  10. Low clarity of scope Planning

In addition, statistical tests were performed to reveal the statistically significant different perspectives that owners and contractors have regarding the causes of OOS. At a 5% statistical significance level, it was shown that owners rated the likelihood of occurrent of two causes higher than contractors, and that contractors rated the relative impact of 10 causes higher than owners.

Also, the strength of correlation between the 56 identified warning signs and the occurrence of OOS was determined through the expert-based study, and used to rank the warning signs from most accurate to least accurate in anticipating that OOS is about to happen. Following are the top five warning signs of OOS:

Top Five Warning Signs of OOS: Category:
       1. Late start of pre-commissioning activities Commissioning
  2. Low wages relative to close by projects Resource management
  3. Growing percentage of critical activities in schedule Execution
  4. Inadequate quality management personnel on site Quality management
  5. Late purchase orders Materials management

All reported findings regarding OOS causes and warning signs were validated by the 42 projects the team tracked through the project-based study. Furthermore, the project-based study demonstrated that the projects that experience significant OOS differ from the projects that succeed in minimizing OOS in five team-related factors, four planning-related factors, two project-related factors, and six execution-related factors.

Reference: (SP334-1)

2 : Significant Impacts of OOS

The projects RT-334 tracked in the project-based study demonstrate that on average:

  1. 15% of total project activities are performed as OOS
  2. This OOS work results, on average, in the following consequences:
    1. 33% increase in construction schedule
    2. 25% increase in construction cost

Furthermore, 26% of the studied projects reported that they spent more than 25% of their construction cost on OOS. Also, 29% of the studied projects reported that they spent more than 25% of their hours performing OOS.

In addition, the experts RT-334 surveyed in the study highly rated the negative impacts of OOS on schedule, productivity, cost, quality, and safety. For example, 85% of the experts reported that OOS causes significant to extreme schedule overrun; 74% reported that OOS causes significant to extreme productivity loss; and 73% reported that OOS causes significant to extreme cost overruns.

Furthermore, the relationship between OOS and 12 lagging performance indicators, spanning five performance areas (i.e., schedule, productivity, cost, quality, and safety), was statistically tested through the project-based study. At 95% statistical confidence level, it was shown that OOS results in:

  1. Cost growth
  2. Lower productivity index (earned/actual)
  3. Higher project hours factor
  4. Schedule growth
  5. Higher project schedule factor
  6. Higher rework percentage
  7. Higher number of drawing revisions
  8. Higher number of non-conformity reports
  9. Higher value of punch-list items

For example, Figure 3 shows the statistically significant inverse relationship between OOS and productivity index, indicating that as the percentage of hours spent on OOS increases, the project productivity index significantly decreases.

Figure 3. Inverse Relationship between OOS and Productivity Index (Earned/Actual)

Statistical analysis of the projects RT-334 tracked through the study showed that a 5% increase in OOS causes, on average, the following consequences:

  1. 10% increase in construction cost
  2. 8.5% drop in labor productivity
  3. 11% increase in construction schedule
  4. 5% increase in rework
Reference: (SP334-1)

3 : Concept File

RT-334 developed 21 recommended concepts for preventing OOS and mitigating its impacts through analyzing data from 88 experts and 42 projects, as well as integrating the collective wisdom of the research team members. The concepts are detailed in the “Concept File” so that each recommended concept is explained through a set of actions to minimize OOS, as well as information about when to apply each of these actions, conditions for successful application, cost implication, targeted outcomes, illustrative examples, and references to other CII research. Overall, The Concept File comprises 164 different actions across four project stages (concept, detailed scope, design, and construction).
Reference: (SP334-1)

Key Performance Indicators

Improved schedule; Improved cost; Improved productivity; Reduced rework

Research Publications

The Out-of-Sequence Decision Support System - SP334-1

Publication Date: 12/2018 Type: Special Publication Pages: 0 Status: Tool

Best Practices for Preventing Out-of-sequence Construction Activities and Minimizing their Impacts - RR334-11

Publication Date: 04/2018 Type: Research Report Pages: 339 Status: Reference

Presentations from CII Events

Session - Best Practices for Preventing Out-of-sequence Construction Activities and Minimizing their Impacts

Publication Date: 08/2017 Presenter: Number of Slides: 75 Event Code: AC2017