Experimental evaluation of vegetation fire risk to timber cladding: The effect of separation distance and wind velocity

Timber cladding is increasingly used for environmental and architectural reasons, yet its response to nearby vegetation fires remains insufficiently quantified, particularly under wind-driven exposure. This study examined flame spread and façade heating from burning wood-wool vegetation adjacent to a timber-clad wall. Experiments used fuel loads of 1 and 2 kg, separation distances of 0, 30 and 50 cm, and wind velocities of 0, 2 and 5 m/s. Wall response was measured using total and radiative heat-flux gauges at 0.4 m height and five Type K thermocouples along the centerline. Separation distance dominated façade thermal demand. Under ambient conditions and 0 cm separation distance, the flame attached to the wall and convection-dominated loading occurred, with peak total heat fluxes of 24 kW/m 2 for 1 kg and 35 kW/m 2 for 2 kg, producing wall temperatures of about 260°C and 290°C. At 30 cm, luminous stand-off reduced heat flux to 14 kW/m 2 and temperatures to 130°C–160°C, while at 50 cm, flame detachment limited exposure to about 6 kW/m 2 and 60°C–80°C. Wind reduced wall-residence time, promoted lift-off and reduced low-height temperature peaks by 30%–60%. Overall, small setbacks under low wind produced the most hazardous façade exposure, whereas larger clearances reduced convective impingement and supported defensible-space guidance for façades.