Flat roofs as an arhitectural solution are now more frequent choice due to the different practicalities of use and designing, but also because of the growing confidence in the quality of thermal insulation and waterproofing materials as a result of progress in the development and improvement of their efficiency. The purpose of this thesis is to analyze and compare the building tehnology of flat unobstructed roofs with regard to the type of material for thermal insulation and waterproofing insulation. The first part of this paper describes the historical development of flat roof , the advantages and disadvantages as well as the impacts that affect them. The role of such roofs in modern architecture has been also explained, and as evidence of increasing popularity, the awards awarded for architectural achievements containing the flat roof as an integral part of the architectural solution are also mentioned. After that classification of flat roofs, their layers, their role and the types of materials from which they can be built has been explained. In the second part of the thesis, the types of materials used for thermal insulation and flat roof waterproofing insulation, their properties, production process, application area and building technology have been elaborated. Costs of execution and the structure of workforce for each flat roof variant were analyzed with regard to the selected materials.