It defines the default behavior for the automatic generation of Mass Zones for each Mass Floor in the Project. Specifying a value here will offset the outside perimeter of a Mass Zone to create the core.

[ObsoleteAttribute("This property is obsolete and will be removed in a future version of Revit. Use CoreOffset instead.")]
public double MassZoneCoreOffset { get; set; }

<ObsoleteAttribute("This property is obsolete and will be removed in a future version of Revit. Use CoreOffset instead.")> _
Public Property MassZoneCoreOffset As Double
	Get
	Set

[ObsoleteAttribute(L"This property is obsolete and will be removed in a future version of Revit. Use CoreOffset instead.")]
public:
property double MassZoneCoreOffset {
	double get ();
	void set (double value);
}