The highlighted wall(s) cannot be joined to the highlighted roof because the roof does not entirely cover the wall(s).
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 26.4.0.0 (26.4.0.0)
Syntax
C#
public static FailureDefinitionId WallNotCoveredByRoof { get; }