Fire spread along inclined combustible surfaces

This study examines how tilt angles of wood-based facades influence flame length, flame spread, and charring. Particle board specimens were exposed to a 33 kW flame for 600 s at tilt angles from –20° to +30°. Results from 18 experiments demonstrate that facade inclination alters thermal exposure and burning behavior. Flame length increased by 30-40 % due to tilt alone when increasing from –20° to +30°, and by up to 290 % when the combustible sample burned, with angle increasing from 0° to +30°. Flame-spread rates rose nearly fourfold over the investigated angle range, accompanied by linear increases in char length, area, and volume. Time to ignition remained nearly constant for tilt angles between –20° and 10°, but decreased for positive angles as flames attached more directly to the surface and surface temperatures increased. Temperature profiles and estimated heat fluxes further demonstrate an enhanced flame–surface interaction with increasing angles. The results show that even moderate deviations from vertical orientation can significantly increase upward flame spread and burning contribution from wooden facade elements. These findings underscore the importance of accounting for facade geometry when developing fire-safety strategies for buildings that incorporate combustible cladding and modern architectural features.