Construction building defects are one of the major challenges and a key concern in the Ethiopian building industry that requires immediate attention. Construction defects minimize the value of buildings, the aesthetic nature, and the function of the built environment that create inconvenience to users (or occupants) and obstruct the smooth operation of buildings. However, most can be avoidable as they occur not only through lack of basic knowledge, but also by non- or misapplication of technical procedures. This lack of focus has negative impacts on cost, duration and resources of projects. Therefore, this research tries to determine the major and most frequent defects, identify their relationships (or root causes) and predict the associated rework rectifying cost in Bahir Dar University Building Projects as case study. In addition, the effects of rework and construction defects and their rework reducing measures are investigated. A questionnaire survey and subsequent interviews along with a detailed analysis of documents are employed to address the research focus. Twenty-seven (27) questionnaires from clients, consultants and contractors were collected in Bahir Dar University building construction projects. From the result, ten (10) major types of construction defects and five (5) common causes of construction defects were recorded. The most frequent types of construction defects are; peeling of paint; defects on door and windows; defects on walls, floors, beams and columns. Similarly, the result indicates that the most common cause of construction defects are workmanship error which attributes 32%, defective material taking 24%, poor supervision taking 24%, design error 19% and poor surface investigation taking 1% of the survey. Based on the findings, this research verified eight (8) impact of rework. Time overrun is ranked first; cost overrun is ranked second and reduction of profit is ranked as third impact of rework. Construction defect and rework reduction mechanisms of periodic site supervision, hiring highly experienced designers and implementing quality control mechanisms are the top three construction reduction mechanisms