In general most megaprojects are finished over the budget and later than initially expected. Despite all industries seem to struggle with achieving the desired performance, the lowest performance is found in projects executed in the oil and gas sector. Furthermore the productivity rates in construction industry are the lowest among other industries and have remained in-line with the 1990s figures. Therefore the main goal is to investigate possible ways of improving the construction productivity in the process industry. This is done by identifying critical factors that are affecting the construction productivity on site. Determining how the construction productivity is tackled during large engineering projects and examining main factors that have influenced the productivity on-site, will help in evaluating the productivity issue as a complex phenomenon. Main findings lead to construction productivity being a sum of decisions made at different points in time. Furthermore effectiveness factor was found to be crucial in facilitating high efficiency on site. Overall, proper understanding and combination of both measurements; effectiveness and efficiency in productivity, is expected to facilitate the desired productivity on site. Context of the projects have been found to play a crucial role in the factors’ evaluation.