Modern structures require more complex designs. There is an increased need for accurate approaches to assessing uncertainties in loads, geometry, material properties, and operational environments. However, information is scarce on the reliability of suspension roofs together with their joints. There is an urgent need for estimating stress-strain state and reliability of welded joints, so recommendations can be given based on the obtained data. In this paper, reliability of large-span suspension roofs was investigated and a fundamental approach is proposed for reliability determination of these joints at the design phase of suspension rod roofs. In this work, several joints were investigated: supporting joints between rigid threads and external/internal contours, intermediate joints of top /lower chords of supporting threads, as well as joints between vertical/horizontal links and supporting thread of a roof. To measure reliability of joints, logic and probabilistic methods were used conjointly with other methods based on mathematical statistics. The proposed approach can be applied to design of suspension roof systems and help to develop better designs for better safety, quality control and efficiency of these structures, providing economic and social benefits.