The impact of different passive protective measures against external vertical firespread was investigated using the numerical tool Fire Dynamics Simulator (FDS).The numerical study was divided into a validation study and a comparative analysis.The validation study was performed to evaluate FDS as a calculation tool for modellingexternal vertical fire spread and was conducted using experimental results from alarge‐scale fire test done on a SP FIRE 105 test rig at SP, Sweden. It was concludedthat FDS 6.2.0 could reproduce the experimental results with a reasonable level ofdetail. In the comparative analysis, the impact on the external fire from a smallerapartment was studied in FDS with different configurations of horizontal projectionsand spandrels in the building exterior. Also, the effects of an upper and lower facadeset‐back configuration were studied. The results show that facade solutions based ona horizontal projection or an upper facade set‐back configuration result in comparableor better protection compared with a defined spandrel height. The results also showthat a spandrel height of at least 1.2 m can be replaced by a 60‐cm‐deep horizontalprojection, given that the balcony is wider than the underlying opening.