The construction industry has developed rapidly, on a local, national, and international level. This rapid development has resulted in increased levels of both physical and non-physical waste produced within the construction sector. To date, the causes, and effects of physical waste are well documented; however, non-physical waste within Ireland and the UK requires further attention. The aim of this study is to investigate the causes, activities, impact, and proposed solutions to non-physical waste on construction sites within the United Kingdom (UK) and Ireland. A qualitative research method is used to address the aim proposed. Semi-structured interviews are conducted to gather information from professionals within the industry with a minimum of two years’ experience. 15 interviewees from 10 different companies participate in the study, with focus on the causes, effects, and solutions to non-physical waste in the construction industry. In total, 26 causes are identified, all of which are grouped into five categories, as follows: Design, Planning, Poor Sub-Contractor Choice, Brexit, and Staff Retention. The respective activities of each category are identified and discussed further. The findings of this study will help construction companies to avoid and reduce the levels of non-physical waste throughout the life cycle of a project. Furthermore, the study makes some suggestions for further solutions to reducing the levels of non-physical waste in the sector, while proposing further research on the topic.