Durability of roofs has been increased by using polymer bituminous material. The most serious problem is reliability of glued seams between the overlap of layers. By analysing this problem the mechanism of seams formation and impact of gluing technology on properties of durability and maintenance such as strength, thickness and appearance of unglued places are analysed. The final thickness of seams is regarded as an additional criterion for seam evaluation. The dependence of seam strength on heating duration of melted surfaces has been determined experimentally. It was found that the maximum strength of seams is about 15–20 % of bituminous roofing membranes and cannot be increased by a gluing technology. The solutions are suggested as pract...