Operations of a building site change and develop and progress all the time. Developing methods of work for building sites is important so that the quality of buildings are improved and employees’ health and ability to work remains stable till retirement. The main goal of the thesis was to research operations of efficient building site and form a system model of an efficient building site. The objective of the system model was to describe the basic functions of building site and observe a closer look to important details in a site. Safety and moisture management are the details that were discussed more specifically. The formed system model of a building site is an agenda to follow through the building project for supervisors. The model provides a basis for action in a building environment and it also helps supervisors to understand the whole building site.