It will be fairly common to have penthouse or mechanical levels above the roof level modeled in the RAM Modeler that have no lateral system in common with the main lateral system. The lateral system of these levels may not even be included in the model. It may be undesirable to have large generated story\diaphragm forces applied to these levels. The user can prevent this for seismic forces by using the Combine option in the Loads - Masses command or for wind forces by using the No Exposure option of the Loads - Exposure command. Note that for generated wind loads, specifying No Exposure on the uppermost level(s) causes the program to ignore those levels entirely (while specifying No Exposure on an intermediate level merely causes the program to distribute the pressures at that story to the adjacent stories).

It may be preferable to model these levels without any lateral members, and allow the program to calculate the story\diaphragm forces without using the Combine option or the No Exposure option as explained above. In that situation, the program calculates the story\diaphragm forces for all levels, then checks to see if the uppermost level(s) have any lateral members. If the upper levels(s) have no lateral members, the calculated story\diaphragm forces are automatically combined down to the highest level that does have lateral members.

Note that in a Dynamic analysis the masses at levels with no lateral members are ignored unless the user combines them to levels below or above.