diff --git a/src/db/db/dbHierNetworkProcessor.cc b/src/db/db/dbHierNetworkProcessor.cc
index bd48e5800..ac1b9e06b 100644
--- a/src/db/db/dbHierNetworkProcessor.cc
+++ b/src/db/db/dbHierNetworkProcessor.cc
@@ -132,6 +132,15 @@ local_cluster<T>::local_cluster ()
   //  .. nothing yet ..
 }
 
+template <class T>
+void
+local_cluster<T>::clear ()
+{
+  m_shapes.clear ();
+  m_needs_update = false;
+  m_bbox = box_type ();
+}
+
 template <class T>
 void
 local_cluster<T>::add (const T &s, unsigned int la)
@@ -241,7 +250,7 @@ local_cluster<T>::interacts (const local_cluster<T> &other, const db::ICplxTrans
 {
   const_cast<local_cluster<T> *> (this)->ensure_sorted ();
 
-  if (! other.bbox ().overlaps (bbox ())) {
+  if (! other.bbox ().touches (bbox ())) {
     return false;
   }
 
@@ -253,7 +262,7 @@ local_cluster<T>::interacts (const local_cluster<T> &other, const db::ICplxTrans
 
   bool any = false;
   for (typename std::map<unsigned int, tree_type>::const_iterator s = m_shapes.begin (); s != m_shapes.end (); ++s) {
-    for (typename tree_type::overlapping_iterator i = s->second.begin_overlapping (common, bc); ! i.at_end (); ++i) {
+    for (typename tree_type::touching_iterator i = s->second.begin_touching (common, bc); ! i.at_end (); ++i) {
       scanner.insert1 (i.operator-> (), s->first);
       any = true;
     }
@@ -264,13 +273,13 @@ local_cluster<T>::interacts (const local_cluster<T> &other, const db::ICplxTrans
   }
 
   for (typename std::map<unsigned int, tree_type>::const_iterator s = other.m_shapes.begin (); s != other.m_shapes.end (); ++s) {
-    for (typename tree_type::overlapping_iterator i = s->second.begin_overlapping (common.transformed (trans.inverted ()), bc); ! i.at_end (); ++i) {
+    for (typename tree_type::touching_iterator i = s->second.begin_touching (common.transformed (trans.inverted ()), bc); ! i.at_end (); ++i) {
       scanner.insert2 (i.operator-> (), s->first);
     }
   }
 
   interaction_receiver<T> rec (conn, trans);
-  return ! scanner.process (rec, 0, bc, bc_t);
+  return ! scanner.process (rec, 1 /*==touching*/, bc, bc_t);
 }
 
 //  explicit instantiations
diff --git a/src/db/db/dbHierNetworkProcessor.h b/src/db/db/dbHierNetworkProcessor.h
index 80e53a1cd..699a41d0c 100644
--- a/src/db/db/dbHierNetworkProcessor.h
+++ b/src/db/db/dbHierNetworkProcessor.h
@@ -125,6 +125,11 @@ public:
    */
   local_cluster ();
 
+  /**
+   *  @brief Clears the cluster
+   */
+  void clear ();
+
   /**
    *  @brief Adds a shape with the given layer to the cluster
    */
diff --git a/src/db/unit_tests/dbHierNetworkProcessorTests.cc b/src/db/unit_tests/dbHierNetworkProcessorTests.cc
index 23176b8fd..f12581415 100644
--- a/src/db/unit_tests/dbHierNetworkProcessorTests.cc
+++ b/src/db/unit_tests/dbHierNetworkProcessorTests.cc
@@ -133,3 +133,97 @@ TEST(2_ShapeInteractionsRealPolygon)
   EXPECT_EQ (conn.interacts (ref1, 1, ref2, 2), false);
   EXPECT_EQ (conn.interacts (ref1, 1, ref1, 2, t2), false);
 }
+
+TEST(10_LocalClusterBasic)
+{
+  db::GenericRepository repo;
+
+  db::Polygon poly;
+  tl::from_string ("(0,0;0,1000;1000,1000;1000,0)", poly);
+
+  db::local_cluster<db::PolygonRef> cluster;
+  EXPECT_EQ (cluster.bbox ().to_string (), "()");
+  EXPECT_EQ (cluster.id (), size_t (0));
+
+  cluster.add (db::PolygonRef (poly, repo), 0);
+  EXPECT_EQ (cluster.bbox ().to_string (), "(0,0;1000,1000)");
+
+  db::local_cluster<db::PolygonRef> cluster2;
+  cluster.add (db::PolygonRef (poly, repo).transformed (db::Trans (db::Vector (10, 20))), 1);
+
+  cluster.join_with (cluster2);
+  EXPECT_EQ (cluster.bbox ().to_string (), "(0,0;1010,1020)");
+}
+
+TEST(11_LocalClusterInteractBasic)
+{
+  db::GenericRepository repo;
+
+  db::Connectivity conn;
+  conn.connect (0);
+  conn.connect (1);
+  conn.connect (2);
+  conn.connect (0, 1);
+  conn.connect (0, 2);
+
+  db::Polygon poly;
+  tl::from_string ("(0,0;0,1000;1000,1000;1000,0)", poly);
+
+  db::local_cluster<db::PolygonRef> cluster;
+  db::local_cluster<db::PolygonRef> cluster2;
+
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+
+  cluster.add (db::PolygonRef (poly, repo), 0);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+
+  cluster2.add (db::PolygonRef (poly, repo), 0);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), true);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (10, 20))), conn), true);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (0, 1000))), conn), true);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (0, 1001))), conn), false);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (0, 2000))), conn), false);
+
+  cluster.clear ();
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+}
+
+TEST(11_LocalClusterInteractDifferentLayers)
+{
+  db::GenericRepository repo;
+
+  db::Connectivity conn;
+  conn.connect (0);
+  conn.connect (1);
+  conn.connect (2);
+  conn.connect (0, 1);
+  conn.connect (0, 2);
+
+  db::Polygon poly;
+  tl::from_string ("(0,0;0,1000;1000,1000;1000,0)", poly);
+
+  db::local_cluster<db::PolygonRef> cluster;
+  db::local_cluster<db::PolygonRef> cluster2;
+
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+
+  cluster.add (db::PolygonRef (poly, repo), 0);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+
+  cluster2.add (db::PolygonRef (poly, repo), 1);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), true);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (10, 20))), conn), true);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (0, 1000))), conn), true);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (0, 1001))), conn), false);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (db::Trans (db::Vector (0, 2000))), conn), false);
+
+  cluster.clear ();
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+  cluster.add (db::PolygonRef (poly, repo), 2);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false); //  not connected
+
+  cluster.clear ();
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), false);
+  cluster.add (db::PolygonRef (poly, repo), 1);
+  EXPECT_EQ (cluster.interacts (cluster2, db::ICplxTrans (), conn), true);
+}