Outbuildings and other flammables Outbuildings such as storage sheds, workshops, play structures, garages and lean-to’s (Fig. 18) in effect, increase the structure density of HIZs. When they ignite and burn, they can become significant ignition sources within the HIZ (see Fig. 13 and discussion). Outbuildings are potentially vulnerable to direct ember ignitions due to gaps and openings at doors, windows, under eaves, etc. The firewood shed (right photo) is highly vulnerable to ember ignition and if burning will assure the home’s destruction. However, outbuildings are commonly ignition vulnerable from fire spreading to them or adjacent debris. For example, the shed in Figure 18 (left photo) has dead grass continuous to the wall, debris at the rear and an adjacent wood fence at the property boundary. Commonly, a wood fence at the property boundary has continuous dead vegetation and debris outside the fence. The destroyed outbuilding in the center photo was next to a wood fence adjacent to continuous wildland vegetation outside. The wildfire burned through continuous vegetation to ignite the fence leading to the shed. Outbuildings are commonly positioned close to homes, potentially becoming critical sources of ignition exposure to adjacent homes.
Figure 18: Outbuildings such as the shed on the left are ignition vulnerable from fire spreading in dead grass, flammable debris or a wood fence to contact and ignite it or directly ignite from burning embers such as the firewood on the right. Once ignited, the burning outbuilding or adjacent firewood ignites the house or business.
Key Finding (7): Fire spread continued through the Lytton Community was principally determined by the highly vulnerable ignition conditions within individual HIZs, and by high structure-to-structure flame spread potential due to overlapping HIZs. Density of structures in Lytton-area communities was commonly increased by placement of highly ignitable sheds, workshops and other flammable materials close to primary structures.
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