The Cured Stage is normally found at the end of the growing season. However, it can develop in the growing season when there is insufficient rainfall. Buildup index is an indicator of the relative dryness of the several inches of surface fuels lying on the ground that are beneath the upper, fresh, thin layer. Drying weather facilitates more fuels becoming available. As the drying of the surface fuels on the ground extends progressively deeper on mineral soils, fire lines become harder to hold.
Fires persist longer and can eventually creep under fire lines or breaks.
This facilitates fire escapes as surface fuels on the other side of the fire line are kindled. Excessively deep surface fuels on mineral soils or the organic soils respond differently to wetting and drying than ordinary fuels on mineral soils. Under these conditions the BUI is not the best indicator to measure dryness. As the BUI increases the width of the burning head fire increases and the flame length increases. Under a well- developed buildup situation, fires are more persistent, burn deeper, and are harder to extinguish.