Application of time buffers to construction project task durations

Marion M. Russell, Gregory Howell, Simon M. Hsiang, Min Liu

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


For this research, a time buffer is defined as the extra time added during planning to individual task durations to compensate for uncertainty and protect against workflow variation to assure a predictable hand-off to subsequent crews. Although previous research has acknowledged this addition of time buffers, their use in practice has not been studied. This paper reports on what causes people to add and size time buffers. A nationwide survey was administered to project managers, superintendents, and foremen to identify the most frequent and severe reasons for adding time buffers to construction task durations. Forty-seven buffer factors were grouped into nine categories: project characteristics, prerequisite work, detailed design/working method, labor force, tools and equipment, material and components, work/jobsite conditions, management/supervision/information flow, and weather. Contributions to the body of knowledge include (1) identifying the 12 most frequent and severe causes of time buffer; (2) analyzing (understanding) how buffers are viewed differently by foremen, superintendents, and project managers, between trades and between general contractors and subcontractors, and the perception among different levels of experience; and (3) investigating how companies that do not regularly use the Last Planner System and those that do view those factors differently. Additionally, the research quantitatively developed risk profiles of the buffer factors through an integrated risk assessment approach. Understanding the application of time buffers and their associated frequency and severity will help construction managers address potential problem areas and inefficiencies in a prioritized manner.

Original languageEnglish (US)
Article number04013008
JournalJournal of Construction Engineering and Management
Issue number10
StatePublished - Oct 2013
Externally publishedYes


  • Buffer
  • Construction
  • Labor and personnel issues
  • Time
  • Uncertainty

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Industrial relations
  • Strategy and Management


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