diff --git a/isometric-park-fna/Engines/BuildToolEngine.cs b/isometric-park-fna/Engines/BuildToolEngine.cs
--- a/isometric-park-fna/Engines/BuildToolEngine.cs
+++ b/isometric-park-fna/Engines/BuildToolEngine.cs
@@ -219,6 +219,19 @@
                     }
                 }
 
+                foreach (var (entity, status) in ReadEntities<AreaComponent>()
+                        .WhereF((e) => HasComponent<ContractStatusComponent>(e))
+                        .SelectWhereF((e) => (e, GetComponent<ContractStatusComponent>(e)),
+                            (e) => ((e.Item2.status != ContractStatus.Broken)
+                                && (e.Item2.status != ContractStatus.Rejected)
+                                && (e.Item2.status != ContractStatus.Expired)
+                                && (e.Item2.status != ContractStatus.Completed)
+                                && (e.Item2.status != ContractStatus.Proposed))
+                            )) {
+                    var entitySquares = GetComponent<AreaComponent>(entity).squares;
+                    occupied.AddRange(entitySquares);
+                }
+
                 foreach (ref readonly var message in ReadMessages<AdjustSelection>()) {
                     foreach (ref readonly   var entity in ReadEntities<SelectedComponent>()) {
                         var selection = GetComponent<SelectedComponent>(entity);
@@ -231,13 +244,17 @@
                             else if(message.Type == AdjustmentType.Complete) {
                                 var point = GetComponent<PointComponent>(entity);
                                 var structure_entity = CreateEntity();
+                                //Verify square is free:
+                                //
+                                if (!occupied.Contains(point.Square)) {
 
-                                AddComponent(structure_entity, new PointComponent {Square = point.Square,
-                                        Tool = point.Tool} );
-                                AddComponent(structure_entity, 
-                                        new StructureComponent { Structure = Structure.Tower});
-                                Destroy(entity);
-                                Logging.Success("Placed Tower!");
+                                    AddComponent(structure_entity, new PointComponent {Square = point.Square,
+                                            Tool = point.Tool} );
+                                    AddComponent(structure_entity, 
+                                            new StructureComponent { Structure = Structure.Tower});
+                                    Destroy(entity);
+                                    Logging.Success("Placed Tower!");
+                                }
 
                             }
                             else {