Construction labour is a significant cost factor for petrochemical plant owners and their contractors. Enhancing labour productivity is therefore indispensable for the petrochemical industry in order to achieve sustainable development. Considering the variety of projects undertaken by this industry (i.e. construction and more particularly, maintenance and shutdowns/turnarounds), there is a lack of standard methods for assessing labour productivity. This generates a need for developing productivity assessment practices suitable for all project types. This paper presents solutions for labour productivity improvement based on a study conducted at various petrochemical plants. The study developed and implemented a modified Activity Analysis method suitable for the site conditions, with a focus on maintenance activities and shutdown/turnaround projects, which were rarely considered on previous productivity assessment approaches. Conducted over two cycles, this study assessed the current labour productivity, identified barriers, and analysed the efficacy of solutions implemented to mitigate these barriers. The aggregate direct work percentage was found to have increased in the second cycle. The analysis of labour productivity through Activity Analysis in maintenance and shutdown/turnaround projects is a key contribution of this study. The findings provide a basis for assessing and benchmarking labour productivity in the petrochemical industry.