diff --git a/src/Mod/Arch/ArchBuilding.py b/src/Mod/Arch/ArchBuilding.py
index 6a2cb2c33..f8ed4e8ca 100644
--- a/src/Mod/Arch/ArchBuilding.py
+++ b/src/Mod/Arch/ArchBuilding.py
@@ -68,12 +68,27 @@ class _Building:
     def __init__(self,obj):
         self.Type = "Building"
         obj.Proxy = self
-
+        self.Object = obj
+        
     def execute(self,obj):
-        pass
+        self.Object = obj
         
     def onChanged(self,obj,prop):
         pass
+
+    def addObject(self,child):
+        if hasattr(self,"Object"):
+            g = self.Object.Group
+            if not child in g:
+                g.append(child)
+                self.Object.Group = g
+        
+    def removeObject(self,child):
+        if hasattr(self,"Object"):
+            g = self.Object.Group
+            if child in g:
+                g.remove(child)
+                self.Object.Group = g
         
 class _ViewProviderBuilding:
     "A View Provider for the Building object"
diff --git a/src/Mod/Arch/ArchFloor.py b/src/Mod/Arch/ArchFloor.py
index f5b9d435e..606395961 100644
--- a/src/Mod/Arch/ArchFloor.py
+++ b/src/Mod/Arch/ArchFloor.py
@@ -71,13 +71,27 @@ class _Floor:
                         "The height of this floor")
         self.Type = "Floor"
         obj.Proxy = self
+        self.Object = obj
 
     def execute(self,obj):
-        pass
+        self.Object = obj
         
     def onChanged(self,obj,prop):
         pass
 
+    def addObject(self,child):
+        if hasattr(self,"Object"):
+            g = self.Object.Group
+            if not child in g:
+                g.append(child)
+                self.Object.Group = g
+        
+    def removeObject(self,child):
+        if hasattr(self,"Object"):
+            g = self.Object.Group
+            if child in g:
+                g.remove(child)
+                self.Object.Group = g
     
 class _ViewProviderFloor:
     "A View Provider for the Cell object"
diff --git a/src/Mod/Arch/ArchSite.py b/src/Mod/Arch/ArchSite.py
index 5da538e5a..300fd09ef 100644
--- a/src/Mod/Arch/ArchSite.py
+++ b/src/Mod/Arch/ArchSite.py
@@ -68,13 +68,28 @@ class _Site:
     def __init__(self,obj):
         self.Type = "Site"
         obj.Proxy = self
+        self.Object = obj
         
     def execute(self,obj):
-        pass
-        
+        self.Object = obj
+    
     def onChanged(self,obj,prop):
         pass
     
+    def addObject(self,child):
+        if hasattr(self,"Object"):
+            g = self.Object.Group
+            if not child in g:
+                g.append(child)
+                self.Object.Group = g
+        
+    def removeObject(self,child):
+        if hasattr(self,"Object"):
+            g = self.Object.Group
+            if child in g:
+                g.remove(child)
+                self.Object.Group = g
+    
 class _ViewProviderSite:
     "A View Provider for the Site object"
     def __init__(self,vobj):