Background and purpose: In a recent century, the amount of construction waste has increased significantly. Although the building industry has a considerable role in the development of a society, it is regarded as an environmentally destructive. Source reduction is the highest goal in the waste management hierarchy and is in priority. It also has economic benefits by reducing costs associated with transportation, disposal or recycling of wastes. The present study is aimed to identify activities generating the wastes in design, transportation and storage and procurement of building materials. Materials and Methods: This was questionnaire survey. A total of 94 professionals in the construction industry were attended in this study. To determine the validity and reliability of the instrument, content validity method and Cronbach’s alpha coefficient (0.79) were used. Data were analyzed using SPSS for Windows. Frequencies, percentage, mean and standard deviation were determined in this research. Results: The results showed that handling and storage have been chosen as the most causative factor of waste production in construction activity. Improper material storage was identified major factor in producing waste in handling and storage phase. Usage of low-quality material in design stage and material price changes in procurement were recognized as major causes of waste production in these stages. Conclusion: All studied phases in this research were identified as causative factors in producing of waste. Identifying causes of construction waste production will help us decide better how to control this sort of wastes.