One of the shortcomings of the F-scale is that it assumes all structures are homogeneously constructed. Variations in structural strength simply aren't considered. As the mean wind speed increases, confidence bands widen. As a result, wind speed ranges will overlap between F-scale categories. Therefore, damage intensity of a structure may actually lie in more than one F-scale category.
Confidence bands widen with increasing variability in the resistance of a structure.
Since this is related to the degree of engineering attention in design of a building, a better degree of confidence in estimating the failure wind speed can be obtained. These two points are illustrated in Table 3. The method incorporates load and resistance statistics to obtain a certain degree of confidence in wind speed assessment. Information can be used from construction plans to calculate the possible range of failure wind speeds. The probabilistic approach shown here is new since advancements using the LRFD method are still being developed.