Background: The construction industry is one business sector where time is of affluence. For this reason, most construction projects have well-stipulated timelines in the schedules to control and manage all sections of the project. Conversely, there are possible expectations beyond reasonable control where the extension of time in construction is necessary. However, extensions do not come cheap. The cost implication which could be very devastating is dependent on the size of the project, the intended project purpose, as well as the new scheduled completion date. Objective: The aim is to determine the causes and cost impact of construction delays leading to time extensions.Furthermore, to suggest guidelines for claim preparation. Methods: This paper reviews severally outlined reasons for project completion delays and cost implications from the various literature on the causes of delays which otherwise triggers time extensions. Results: Time extension are as a result of delays causing time overrun during the execution phase of projects. The literature suggest several factors play a role in triggering time extension, thus the need to identify each of the contributing factors at every phase of execution. These are either excusable (compensable and non-compensable) and nonexcusable (non-compensable). Conclusions: The analysis of the factors and the resulting impacts proves to burden stakeholders sometimes with high financial constraints, triggering confusion and prolonging project completion times. The causes of time extension though vary from project to project; the underlying impacts are similar. Consequently, there is the need to document and use appropriate means to evaluate requested time extension for appropriate resolution of dispute during the project execution.