The issue of a sufficiently reliable overheads estimation is vital for the potential contractor. According to the research presented in one of the previous works by Plebankiewicz and Leśniak [33] the influence of improper calculation of the overhead costs can be significant for the financial situation of the contracting company. Generally, the building contractor’s overhead costs are divided into two categories: site (project) overhead costs and company’s (general) overhead costs [32]. Site (project) overhead costs include items that can be identified with a particular job, but not materials, labour, or production equipment. Company’s overhead costs are items that represent the cost of doing business and often are considered as fixed expenses that must be paid by the contractor. In literature one can find different definitions of overhead costs [1,5,26,33,36]. On the other hand, an overhead cost of a construction project can be defined as a cost that cannot be identified with or charged to a construction project or to a unit of construction production [21]. Cilensek [19] describes overhead costs as those that are not a component of the actual construction work but are incurred by the contractor to support the work. The overheads include expenses that cannot be charged directly to a particular branch of work but are required to construct the project [23]. According to Polish standards of cost estimating [38], site overhead costs can be defined as all the costs incurred by the contractor on the building site in connection with the works realization, excluding the direct costs. Overhead costs are widely discussed in literature. Relevant research on overhead costs can be divided into four main research trends [36]. Some of the researchers focus on the analysis of situation and statistical research on the understanding of the overhead costs concept, analysis of construction delays vs. overhead costs, analysis of the construction company’s overhead costs distribution, and allocation and analysis of fixed expenses recovering. Assaf et al. [6] investigated the overhead costs practices and showed how the unstable construction market makes it difficult for construction companies to decide on the optimum level of overhead costs. The practices of estimating overhead costs are investigated in various countries (e.g. Great Britain [14], the USA and Canada [30], Lithuania [36], Saudi Arabia [6], Poland [33]). Particular attention is paid to a detailed computation of site overheads. A number of empirical studies relate to the determination of the project overhead cost. Factors that influence project overhead cost are widely discussed in literature in various aspects [5,17,40]. Some ofthem emphasize that project time is an important factor affecting project overheads [11,27]. Cooke [20] highlighted that the location of the site could affect a number of project overhead items. Brook [11] indicated that the method of work was a critical factor affecting the amount spent on project overheads.