The level of Building Information Modelling (BIM) and Lean adoption has been rapidly increased. The benefits of integrating these two approaches have also been identified. However, to achieve the maximum benefits of the interaction of these two approaches, there needs to be assessment tools to analyse their performances collectively. Because understanding and analysing the performances of these approaches would provide value to the entire project in terms of lessons learned, more value generation, and continuous improvements. Therefore, this paper aims to propose an integrated BIM and Lean Maturity Model based on reviewing the literature around current maturity models. This paper proposes an Integrated BIM and Lean Maturity Model named 'IDEAL' which could serve as a basis in terms of assessing the performances of the projects implementing BIM and Lean together.