Building Information Modelling (BIM) is transforming the construction industry by improving project efficiency, accuracy, and teamwork. However, failure to determine accurately soft costs during BIM-based construction projects can lead to financial uncertainty and management issues, making it difficult to assess the return on investment (ROI) of BIM. Identifying the factors that influence BIM-related soft costs is crucial for determining the ROI of BIM. To address this issue, this study aimed to investigate the factors affecting soft costs in BIM-based construction projects, using Malaysia as a case study. Data collection involved conducting semi-structured interviews with BIM professionals, followed by thematic analysis to analyse the collected data. The findings revealed that the factors influencing soft costs can be categorised into two main themes: organisational factors and project factors. Within the former, the subthemes included development charges, certification fees, commissioning fees, and ongoing maintenance costs. Meanwhile, project factors encompassed contingency fees, levy fees, and documentation fees. Understanding these factors is crucial for determining the ROI of BIM, which can drive more widespread BIM implementation in developing countries. The study reveals that accurately identifying the factors influencing soft costs in BIM-based construction projects is essential for effective cost management. As a result, the findings emphasise that these factors must be addressed in order to improve financial planning and project execution in the construction industry. The originality of this study lies in its focus on soft costs within BIM-based construction projects, an underexplored area of the existing literature. This nuanced understanding will help organisations and policymakers to manage costs more effectively, contributing to more efficient construction practices and supporting the UN Sustainable Development Goals 9: Industry, Innovation, and Infrastructure and 11: Sustainable Cities and Communities by promoting sustainable building practices and resilient infrastructure development.

Purpose
Building information modeling (BIM) offers numerous benefits for construction projects, but its implementation can include additional non-physical costs, commonly referred to as soft costs, distinct from traditional construction projects. Hence, understanding the soft cost elements (SCEs) is critical for accurate cost estimation in BIM-based construction projects. This study aims to identify the critical SCEs in BIM-based construction projects.

Design/methodology/approach
This study conducted a multi-stage approach, starting with an SLR to compile an initial list of SCEs, which was refined through a pilot test with BIM experts. A Delphi survey conducted with 16 experts evaluated the SCEs for two rounds. Data analysis included mean values and percentage of agreement analyses to identify the critical SCEs. Finally, a thematic analysis was conducted to categorize the critical SCEs.

Findings
This study identified eight critical SCEs in BIM-based construction projects, categorized into two categories: technology and human resources. Technology-related costs include BIM software, hardware, updates and BIM-specific planning/designing. Human resource-related costs encompass BIM consultant, modeler, coordinator and manager remuneration.

Originality/value
This is the first study to determine the critical SCEs in BIM-based construction projects. Understanding the critical SCEs provides stakeholders with actionable insights for developing strategies to improve the cost management of SCEs in BIM-based construction projects.