Performance fire tests on building external walls made of sandwich panels

External walls are part of the construction system where new solutions appear every day. These systems are usually built with new materials that offer greater thermal resistance but with poor fire behaviour. This fire behaviour can be evaluated in large-scale tests, such as the ones prescribed at BS 8414-1, LEPIR II or ISO-13785-1 standards, that consider a typical scenario where the fire outbreaks inside the building and spreads to outside through a window or venting. However, there are situations in which these systems can be affected by external fires, such as forest fires, goods burning next to the external wall, or even sabotage, that are of interest to be evaluated. This paper presents the results of experimental tests for evaluating the behaviour of building external walls made of sandwich panels, of four different insulation materials in the core (mineral wool, polyisocyanurate - PIR, organic polymer and polyurethane - PUR). The tests were carried out according to BS 8414-2 standard, considering the common internal and a new external fire scenario. The external fire scenario was intended to simulate the case of goods or equipment stored next to the wall, outside the building, that catches fire. The walls' performance was checked according to BRE 135 Annex B criteria. In these tests were registered the temperatures in the exposed and unexposed face of the walls and the incident radiant heat flux in the wall surface. The external fire scenario showed that can be more aggressive to the external wall cladding than the internal fire, demonstrating that this condition must be carefully investigated to propose this situation in standards for the future.