Experimental tests on fire behaviour of roof covering systems

External fire exposure represents a significant risk to roof covering systems, especially in wildfire-prone and industrial areas. This study presents the results of an extensive experimental campaign designed to evaluate the fire performance of low-slope roofing systems commonly used in commercial and industrial buildings. Four roof covering solutions have been tested, combining two types of waterproof membranes—polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO)—with two different insulation cores—mineral wool and polyisocyanurate (PIR). The experimental procedures were based on the CEN/TS 1187-Test 1 method and assessing their estimated classification with the EN 13501-5 B ROOF(t1) criteria. The specimens were tested at two installation pitches (1.41° and 15°) and two wind conditions (no wind and with wind of 1.5 m.s -1 ). The study evaluated the influence of roof pitch, joint positioning, membrane type, insulation core, and wind on flame spread and temperature profiles. Results revealed that TPO membranes, especially when combined with PIR insulation, significantly increased flame spread and sustained combustion; however, they did not meet all the criteria for B ROOF(t1) classification in several configurations. Conversely, PVC membranes demonstrated superior fire performance, limiting flame spread and self-extinguishing the flames in different test conditions. Despite these differences, all tested solutions effectively prevented fire penetration and internal ignition. These findings underscore the need for careful selection of roofing components, particularly in high-risk areas, and highlight the importance of wind effect in fire testing of roofing systems.