Investigation of thermally-induced loads in modified bituminous roofing membranes

When exposed to various thermal conditions, installed roofing membrane experiences dimensional change, which creates induced, loads on the membrane material. These loads can cause a number of undesirable effects such as the membrane separating away from the parapet wall, seam components splitting, membrane tear at the vicinity of fasteners and membrane slag causing blistering. This paper deals with two kinds of thermally-induced loads, namely, reversible thermal expansion/contraction and irreversible stress releasing. The mechanisms for each type of induced load have been explored in detail on two membrane types of different internal structure. Thermal conditions are configured in the experiments to simulate typical Canadian summer and winter temperatures on a black roofing membrane surface. This study also explores the role of the membrane's length and pre-loading on the induced loads. Based on limited data, some practical recommendations are given, such as regarding the influence of the induced loads in the membrane and on the performance integrity of the roofing assembly constructions when subjected to various exposure conditions.