Because NBC Figure I-15 is only applicable to flat-roofed buildings, a decision was made to apply the external pressure coefficients for walls, C_p, to the vertical projection of roof panels. However, the coefficient applied to leeward roofs was not following the wall coefficient calculation based on height to depth ratio. Instead it was using the worst-case leeward wall coefficient, -0.5, resulting in heavier-than expected loading for h/d ratios less than 1. This has been corrected and the program is applying the coefficients 0.27( H/D) for 0.25 < H/D < 1.0 and 0.3 for h/d < .25. Note that for buildings in these ranges are ordinarily designed using the low-rise method, I-7, but Shearwalls does not use this method for multi-block structures, and it is likely not be used for flat roofs, so this problem is likely to have occurred for these types of structures.