To Create Slab/Roof Slab Interference Conditions

Use the following procedure to create either additive or subtractive interference conditions for a slab or roof slab.

Just as you can use another object to define the perimeter of a hole you want to add to a slab or a roof slab, you can also modify the geometry of a slab or roof slab by using another object to create an interference condition within the slab or roof slab. Unlike the object used to add a hole, which has no connection to the slab or roof slab and can be erased after the hole is added, the object used to create an interference condition remains partially or wholly embedded in the slab or roof slab, cutting out and replacing a part of its geometry. All interference conditions are subtractive in this sense, but the shrinkwrap effect option you use to create the interference condition (Additive or Subtractive) determines whether the outline of the interference condition is included in or excluded from the shrink wrap outline of the slab or roof slab in plan view.

Typically, after creating interference conditions for a slab or roof slab, you freeze the layer where the interfering objects are placed. If you move or edit the objects, the slab or roof slab updates accordingly. If you want to create both additive and subtractive interference conditions, you need to perform the procedure separately for each type.

Note: Objects used as interference conditions are not included for the Area in the LIST command or in a Schedule Query result.

1. Create one or more objects in the actual location where you want the interference condition positioned in relation to the slab or roof slab.
2. Select the slab or roof slab.

   If the object selected is…	Then…
   a slab	click Slab tabModify panelInterference Condition drop-downAdd.
   a roof slab	click Roof Slab tabModify panelInterference Condition drop-downAdd.

3. Select the objects to use as interference conditions, and press Enter.
   Note: AEC objects from externally referenced (xref) files can be added to a slab or roof slab as interference conditions so long as the following conditions are met:

   • The object is a three-dimensional (3D) body
   • The xref is found
   • The xref is read/write
   • The xref is not locked or opened by another user
   • The xref is loaded
4. Specify the desired shrinkwrap effect.

   If you want to…	Then…
   include the interference condition(s) within the shrink wrap outline in plan view	enter a (Additive).
   exclude the interference condition(s) from the shrink wrap outline in plan view	enter s (Subtractive).

   The selected objects are added to the slab or roof slab as either additive or subtractive interference conditions. You can delete an interference condition or change its shrinkwrap effect using the Interference Conditions worksheet.