Index: Core/Common/src/Core.Common.Gui/Forms/ViewHost/AvalonDockViewHost.xaml
===================================================================
diff -u -rfea3ed82dfb6dfcad535eef16efcbaa9c01564ed -rdc82459b6adaa2473b0459db3f2ee20455277ab8
--- Core/Common/src/Core.Common.Gui/Forms/ViewHost/AvalonDockViewHost.xaml	(.../AvalonDockViewHost.xaml)	(revision fea3ed82dfb6dfcad535eef16efcbaa9c01564ed)
+++ Core/Common/src/Core.Common.Gui/Forms/ViewHost/AvalonDockViewHost.xaml	(.../AvalonDockViewHost.xaml)	(revision dc82459b6adaa2473b0459db3f2ee20455277ab8)
@@ -49,19 +49,29 @@
                     </StackPanel>
                 </DataTemplate>
             </xcad:DockingManager.AnchorableHeaderTemplate>
-        <xcad:LayoutRoot>
-                <xcad:LayoutPanel Orientation="Horizontal">
+            <xcad:LayoutRoot>
+                <xcad:LayoutPanel Orientation="Horizontal" x:Name="leftRightLayoutTarget">
                     <xcad:LayoutAnchorablePaneGroup x:Name="leftLayoutAnchorablePaneGroup" Orientation="Vertical" DockWidth="260">
                         <xcad:LayoutAnchorablePane />
                     </xcad:LayoutAnchorablePaneGroup>
-                    <xcad:LayoutPanel Orientation="Vertical">
+                    <xcad:LayoutPanel Orientation="Vertical" x:Name="bottomLayoutTarget">
                         <xcad:LayoutDocumentPaneGroup x:Name="layoutDocumentPaneGroup">
-                            <xcad:LayoutDocumentPane />
+                        <xcad:LayoutDocumentPane />
                         </xcad:LayoutDocumentPaneGroup>
+                        <xcad:LayoutAnchorablePaneGroup>
+                        <xcad:LayoutAnchorablePane>
+                            <xcad:LayoutAnchorable x:Name="dummyPanelA"></xcad:LayoutAnchorable>
+                        </xcad:LayoutAnchorablePane>
+                        </xcad:LayoutAnchorablePaneGroup>
                         <xcad:LayoutAnchorablePaneGroup x:Name="bottomLayoutAnchorablePaneGroup" DockHeight="200">
                             <xcad:LayoutAnchorablePane />
                         </xcad:LayoutAnchorablePaneGroup>
                     </xcad:LayoutPanel>
+                    <xcad:LayoutAnchorablePaneGroup>
+                        <xcad:LayoutAnchorablePane>
+                            <xcad:LayoutAnchorable x:Name="dummyPanelB"></xcad:LayoutAnchorable>
+                        </xcad:LayoutAnchorablePane>
+                    </xcad:LayoutAnchorablePaneGroup>
                     <xcad:LayoutAnchorablePaneGroup x:Name="rightLayoutAnchorablePaneGroup" Orientation="Vertical" DockWidth="220">
                         <xcad:LayoutAnchorablePane />
                     </xcad:LayoutAnchorablePaneGroup>
Index: Core/Common/src/Core.Common.Gui/Forms/ViewHost/AvalonDockViewHost.xaml.cs
===================================================================
diff -u -rd52aa340885d10c5932c381d4283062c8dddd76b -rdc82459b6adaa2473b0459db3f2ee20455277ab8
--- Core/Common/src/Core.Common.Gui/Forms/ViewHost/AvalonDockViewHost.xaml.cs	(.../AvalonDockViewHost.xaml.cs)	(revision d52aa340885d10c5932c381d4283062c8dddd76b)
+++ Core/Common/src/Core.Common.Gui/Forms/ViewHost/AvalonDockViewHost.xaml.cs	(.../AvalonDockViewHost.xaml.cs)	(revision dc82459b6adaa2473b0459db3f2ee20455277ab8)
@@ -56,6 +56,8 @@
         public AvalonDockViewHost()
         {
             InitializeComponent();
+            dummyPanelA.Hide();
+            dummyPanelB.Hide();
 
             toolViews = new List<IView>();
             documentViews = new List<IView>();
@@ -169,6 +171,7 @@
             SetFocusToView(view);
 
             layoutAnchorable.Hiding += OnLayoutAnchorableHiding;
+            layoutAnchorable.Closing += OnLayoutAnchorableClosing;
         }
 
         public void Remove(IView view)
@@ -185,12 +188,14 @@
                     SetFocusToView(view);
                 }
 
-                GetLayoutContent<LayoutDocument>(view).Close();
+                var layoutDocument = GetLayoutContent<LayoutDocument>(view);
+                layoutDocument.Close();
                 UpdateDockingManager();
             }
             else if (toolViews.Contains(view))
             {
-                GetLayoutContent<LayoutAnchorable>(view).Hide();
+                var layoutAnchorable = GetLayoutContent<LayoutAnchorable>(view);
+                layoutAnchorable.Hide();
                 UpdateDockingManager();
             }
 
@@ -303,7 +308,7 @@
 
         private void OnLayoutDocumentClosing(object sender, CancelEventArgs e)
         {
-            var layoutDocument = (LayoutDocument) sender;
+            var layoutDocument = (LayoutDocument)sender;
             var view = GetView(layoutDocument.Content);
 
             if (ActiveDocumentView == view)
@@ -315,23 +320,34 @@
             }
         }
 
+        private void OnLayoutAnchorableHiding(object sender, CancelEventArgs eventArgs)
+        {
+            var layoutAnchorable = (LayoutAnchorable)sender;
+
+            layoutAnchorable.Hiding -= OnLayoutAnchorableHiding;
+            layoutAnchorable.Closing -= OnLayoutAnchorableClosing;
+
+            layoutAnchorable.Close();
+            OnViewClosed(GetView(layoutAnchorable.Content));
+
+            eventArgs.Cancel = true;
+        }
+
         private void OnLayoutDocumentClosed(object sender, EventArgs e)
         {
-            var layoutDocument = (LayoutDocument) sender;
+            var layoutDocument = (LayoutDocument)sender;
 
             layoutDocument.Closing -= OnLayoutDocumentClosing;
             layoutDocument.Closed -= OnLayoutDocumentClosed;
 
             OnViewClosed(GetView(layoutDocument.Content));
         }
 
-        private void OnLayoutAnchorableHiding(object sender, CancelEventArgs e)
+        private void OnLayoutAnchorableClosing(object sender, CancelEventArgs e)
         {
-            var layoutAnchorable = (LayoutAnchorable) sender;
-
-            layoutAnchorable.Hiding -= OnLayoutAnchorableHiding;
-
-            OnViewClosed(GetView(layoutAnchorable.Content));
+            var layoutAnchorable = (LayoutAnchorable)sender;
+            layoutAnchorable.Hide();
+            e.Cancel = true;
         }
 
         private void OnViewClosed(IView view)
@@ -388,19 +404,35 @@
 
         private void AddLayoutAnchorable(LayoutAnchorable layoutAnchorable, ToolViewLocation toolViewLocation)
         {
-            var layoutAnchorablePaneGroup = new LayoutAnchorablePaneGroup();
-
+            LayoutAnchorablePaneGroup layoutAnchorablePaneGroup = null;
             switch (toolViewLocation)
             {
                 case ToolViewLocation.Left:
+                    if (leftLayoutAnchorablePaneGroup.Parent == null)
+                    {
+                        leftLayoutAnchorablePaneGroup.Children.Add(new LayoutAnchorablePane());
+                        leftRightLayoutTarget.Children.Insert(0, leftLayoutAnchorablePaneGroup);
+                    }
                     layoutAnchorablePaneGroup = leftLayoutAnchorablePaneGroup;
                     break;
                 case ToolViewLocation.Bottom:
+                    if (bottomLayoutAnchorablePaneGroup.Parent == null)
+                    {
+                        bottomLayoutAnchorablePaneGroup.Children.Add(new LayoutAnchorablePane());
+                        bottomLayoutTarget.Children.Add(bottomLayoutAnchorablePaneGroup);
+                    }
                     layoutAnchorablePaneGroup = bottomLayoutAnchorablePaneGroup;
                     break;
                 case ToolViewLocation.Right:
+                    if (rightLayoutAnchorablePaneGroup.Parent == null)
+                    {
+                        rightLayoutAnchorablePaneGroup.Children.Add(new LayoutAnchorablePane());
+                        leftRightLayoutTarget.Children.Add(rightLayoutAnchorablePaneGroup);
+                    }
                     layoutAnchorablePaneGroup = rightLayoutAnchorablePaneGroup;
                     break;
+                default:
+                    throw new InvalidEnumArgumentException("toolViewLocation", (int)toolViewLocation, typeof(ToolViewLocation));
             }
 
             layoutAnchorablePaneGroup.Descendents()