Selection of contract type in construction contracts: Lump-Sum, Target-cost and Cost-plus contracts

The construction contract is a document which governs the business relationship of Contractor and Employer for the duration of a construction project. However, the selection of the contract type for the project tends to be performed too shallowly. The present thesis aims to analyse how the contract type is chosen among the three paradigmatic contracts considered here: lump-sum contracts, target-cost contracts and cost-plus contracts. The basis of the study is a case study performed on Project X, a large mine construction project in Western Europe. The relevant literature to the subject was reviewed, mainly the principal-agent theory, literature on risk allocation and on contract selection. After identifying several factors which may influence the contract selection in the literature and in a preliminary interview, a survey was conducted to assess their relative influence in general and in particular for the Project X. The survey was responded by a small sample of highly qualified and experienced managers. and was complemented with in-depth interviews with the majority of them. Some research on the project and on contract documents of the NEC standard contract was also performed in order to provide a context of the characteristics of Project X. The findings of the three sources made it possible to confirm the influence on the selection of the contract type of many of the factors proposed. It was possible to shortlist a small number of factors which influenced the most the selection of the contract type for Project X. These were the preferred risk allocation by the parties, the ability to adapt the contract to scope changes, the knowledge of each contract type by the contracting parties, the improvement of the project delivery by the contract type and the aim to enhance cooperation between the parties. Factors not present in previous research were also discovered, such as the different financial costs of the contract types and the requirement of financial information by the funders of the parties. The very different opinions of the respondents to the survey and interviews regarding the selection of the contract type confirm that the parties should consider in more detail that complex process, because by now the parties are not really sure why they are choosing a certain contract type. Further research should be performed in the future to analyse the factors which influenced the contract type selection in other projects. The projects could also be analysed during their whole duration. Other contract types or variants of the three contract types studied in this thesis could also be added to the analysis