Effect of Gypsum Underlay

The program does not consider gypsum underlay in deflection calculations; it uses the shear deformation and nail slip values for the structural wood panel. When using the four-term equation SDPWS C4.3.2-1 there is no explicit guidance in SDPWS on gypsum underlay, but this approach is consistent with one used with the three-term equation, in that the G_a values used in the combined shear and nail slip term are the same in Table 4.3A for wood panels as those in Table 4.3B for wood panels with gypsum underlay.