Base pressure contour for raft footing is available for the envelop of the loads in Space Gass but not in STAAD. It is important to have this feature be implemented in STAAD too to facilitate the raft footing design based on allowable bearing pressure.
"Load envelope" not "load case"
Thank you for posting this idea. However the capability already exists. In the Diagrams> Plate Stress Contour, select the Base Pressure option for the required load case, e.g.