The Impact of Design Documents on Time and Cost Overruns of Public Construction Projects in Ethiopia and Mitigation with BIM Implementation – a Case Study

Timely completion of public building projects within the allocated budget and in the required quality is paramount for effectively using a facility to provide the intended public services properly. Typically, project owners plan to build public building projects following a critical demand from users. However, public projects in Ethiopia are experiencing considerable delaying until completion. Additional costs beyond the initially planned budget are required as well. This research studied factors that cause time and cost overruns in public building construction in Ethiopia. The study investigated Ethiopia's three public projects of equivalent nature and complexity (size, height, and volume) by implementing the case study research method. These projects were government funded, so the budget shortage was not a reason for the construction delay in any way. The conventional Computer-Aided Design (CAD) method was implemented to design the projects. The projects were executed with the traditional Design-Bid-Build project delivery method. The contract type that was implemented was the Unit-price (admeasurements). Factors that cause Time and cost overruns were identified, and the resulting quantities of delay (in days) and cost (in US Dollars) were registered. Design-document problems, one of the factors believed to cause considerable time and cost overruns, were analyzed in detail. All the design-related problems that cause Time and cost overruns were identified. The additional days and costs incurred with each design problem in all three projects were registered and investigated. Accordingly, among other factors, the result indicated that problems related to design documents had caused a considerable extent of time and cost overruns. Significant findings were (1) the degree of occurrence of Time and cost overruns was high—about 146.6% and 36.8% of the original contract, respectively. (2) 45.3% of the Time Overrun was caused by problems related to design documents, whereas 54.7% was caused by problems different from design documents. (3) Problems in design documents caused time and cost overruns of 45.3% and 51.6%, respectively. On the other hand, improving the quality of design documents was necessary to mitigate problems related to design documents that cause time and cost overruns so that timely completion of projects within budget would be possible. With the help of an explanatory case study research method to validate the study, it is explained that the implementation of BIM could help to prepare design documents with better quality. 13 projects in which BIM was implemented in one or more of their stages in the design process were analyzed and it was found out that, for every factor that causes design-document problems, there are one or more BIM solutions. Studies indicated that (4) the use of BIM could facilitate the preparation of design documents by 50%, (5) save construction costs by 52.36%, and (6) complete the construction of projects within schedule.