AbstractFire accidents caused by the use of open gas torching during roof‐installation work have led to considerable costs, and between 1985 and 1990 such costs reached 249 Million SKr. The Swedish Fire Protection Association together with the roofing contractors association reached agreement on the education and certification of roofers. Meanwhile, the insurance companies started to demand welding methods with lower temperatures and less fire hazard. This resulted in a marked decrease in fires and in a sharp decrease in the amounts paid out by insurance companies (187 million SKr in 1989, 25 million SKr in 1990 and 2.4 million SKr in 1991). This paper summarises the results of a study of the new welding methods, replacing conventional gas torching, for the installation of polymer‐modified bituminous roof‐coverings on flat roofs. In all eight different welding methods were evaluated in Stockholm during the installation in October 1992. Four different products of single‐ply roof‐coverings, namely one of atactic polypropylene (APP)‐modified bitumen and three of styrene–butadiene–styrene copolymer (SBS)‐modified bitumen, were studied. The study comprises temperature measurements during welding jobs on‐site to evaluate fire hazard, and laboratory measurements of T‐peel strength of the seams in order to evaluate the quality of the seam samples prepared on‐site. The results showed that by these new welding methods a remarkable decrease in temperatures by weld was made without any significant change in the quality of the seams. However, the mechanical strength of the seam was related to welding speed, which should be limited to form sufficiently strong s
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