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Wind-Driven Fire Spread to a Structure from Fences and Mulch



Kathryn Butler, Erik L. Johnsson, Alexander Maranghides, Shonali Nazare, Marco G. Fernandez, Rachel McIntyre, William Saar, Mariusz Zarzecki, Wei Tang, Eric Auth, Michael Pryor, Colin McLaughlin


A series of field experiments was conducted to examine the effects on fire spread toward a structure for combustible fences and mulch under conditions that may be encountered in a wildland-urban interface (WUI) fire. The fire behavior of a variety of materials, designs, and configurations were studied under various wind conditions. The 187 experiments were split into five categories: mulch only, fence only, fence plus mulch, parallel fences, and long range firebrand experiments. Fence materials included western redcedar, California redwood, pine, vinyl, and wood-plastic composites, and fence styles included privacy, lattice, and good neighbor (board on board). The tested mulch types were shredded hardwood, mini pine bark nuggets, pine straw, rubber, and artificial turf. A wind machine provided a mean wind speed between 6 m/s and 14 m/s (13 mi/h to 31 mi/h). The fence and/or mulch bed was ignited by a propane burner on the ground at the end farthest from the structure. A small structure was located between 0 m and 1.83 m (0 ft to 6 ft) downwind of the fence or mulch bed as a target for flames and firebrands. A target mulch bed at the base of the structure tested the ability of firebrands produced by the burning fence and mulch bed to ignite spot fires that threatened the structure.
Technical Note (NIST TN) - 2228
Report Number


Fences, fence fires, parallel fences, mulch, firebrands, embers, fire spread, structural ignition, structure vulnerability, wildland-urban interface fires, WUI fires, wind-driven fires


Butler, K. , Johnsson, E. , Maranghides, A. , Nazare, S. , Fernandez, M. , McIntyre, R. , Saar, W. , Zarzecki, M. , Tang, W. , Auth, E. , Pryor, M. and McLaughlin, C. (2022), Wind-Driven Fire Spread to a Structure from Fences and Mulch, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed May 29, 2024)


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Created August 10, 2022, Updated November 29, 2022