Fig. 3 shows the roles of various stakeholders involved in project tendering stage, and the interactive relationships between them. In the tendering stage, project owner, the sponsors and the tenderer become the key customers in transforming the concept to the reality through effective project delivery. Therefore, the cost estimation at the tender stage requires realistic estimation with reference to the tender bids. Moreover, as the project has been approved from the clients, the tenderers' participation in the bidding process becomes eminent and thus the tenderers become one of the key customers of cost estimation. Since the approval of the project has been obtained, business development team is not responsible for cost estimation anymore in this stage. Instead, major cost estimation work is to be done by the tenderers in order to determine the validity of their bidding potentials. Compared to the inception stage, more detailed cost estimation has to be done in this stage, therefore a number of factors from compliance issues, contractual conditions as well as external forces come into concern (refer to Table 3). All these complications will eventually lead into cost overruns in absence of appropriate integration and ill-practices of risk assessment and management.At this stage, the roles of subcontractors and their effectiveness in service delivery should be considered through the main contractor's bid. Buildability issues in terms of design complexity and accessibility issues related to the site conditions as well as direct or indirect stakeholders should be thoroughly integrated in the cost estimation process.