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The purpose of this paper is to identify factors affecting cost estimate accuracy in each of five design stages preceding building construction: order of magnitude, conceptual/schematic, detailed design, construction document and bid phase.

Data were collected using an online survey completed by 138 respondents who work in design consultancy firms in Jordan, including project managers, architects and quantity surveyors (QSs). Survey responses were analyzed using descriptive statistics. Confirmatory interviews and case study comparisons were used to confirm the statistical analysis results.

The results of this study indicated that each design stage’s cost estimate was affected by several factors. Two significant factors were common across four of the five design stages: client experience and project team experience. In addition, a high level of agreement was observed among the project managers, architects and QSs regarding the factors affecting cost estimate accuracy.

Accurately estimating building construction costs during the design process has posed a challenge for designers and their clients in Jordan. Despite the care and effort involved in preparing cost estimates in each of the five design stages, deviations are commonly observed. Because the accuracy of building construction cost estimates directly affect the success or failure of a project, the results of this study can be used to reduce uncertainties in building construction cost estimation and subsequently increase the likelihood of project success