diff --git a/nestkernel/connection_manager.cpp b/nestkernel/connection_manager.cpp
index b614e69d84..e2df068af8 100644
--- a/nestkernel/connection_manager.cpp
+++ b/nestkernel/connection_manager.cpp
@@ -41,8 +41,10 @@
 // Includes from nestkernel:
 #include "clopath_archiving_node.h"
 #include "conn_builder.h"
+#include "conn_builder_conngen.h"
 #include "conn_builder_factory.h"
 #include "connection_label.h"
+#include "connection_manager_impl.h"
 #include "connector_base.h"
 #include "connector_model.h"
 #include "delay_checker.h"
@@ -95,6 +97,20 @@ nest::ConnectionManager::initialize( const bool adjust_number_of_threads_or_rng_
 {
   if ( not adjust_number_of_threads_or_rng_only )
   {
+    // Add connection rules
+    register_conn_builder< OneToOneBuilder >( "one_to_one" );
+    register_conn_builder< AllToAllBuilder >( "all_to_all" );
+    register_conn_builder< FixedInDegreeBuilder >( "fixed_indegree" );
+    register_conn_builder< FixedOutDegreeBuilder >( "fixed_outdegree" );
+    register_conn_builder< BernoulliBuilder >( "pairwise_bernoulli" );
+    register_conn_builder< PoissonBuilder >( "pairwise_poisson" );
+    register_conn_builder< TripartiteBernoulliWithPoolBuilder >( "tripartite_bernoulli_with_pool" );
+    register_conn_builder< SymmetricBernoulliBuilder >( "symmetric_pairwise_bernoulli" );
+    register_conn_builder< FixedTotalNumberBuilder >( "fixed_total_number" );
+#ifdef HAVE_LIBNEUROSIM
+    register_conn_builder< ConnectionGeneratorBuilder >( "conngen" );
+#endif
+
     keep_source_table_ = true;
     connections_have_changed_ = false;
     get_connections_has_been_called_ = false;
@@ -137,7 +153,7 @@ nest::ConnectionManager::initialize( const bool adjust_number_of_threads_or_rng_
 }
 
 void
-nest::ConnectionManager::finalize( const bool )
+nest::ConnectionManager::finalize( const bool adjust_number_of_threads_or_rng_only )
 {
   source_table_.finalize();
   target_table_.finalize();
@@ -146,6 +162,16 @@ nest::ConnectionManager::finalize( const bool )
   std::vector< std::vector< ConnectorBase* > >().swap( connections_ );
   std::vector< std::vector< std::vector< size_t > > >().swap( secondary_recv_buffer_pos_ );
   compressed_spike_data_.clear();
+
+  if ( not adjust_number_of_threads_or_rng_only )
+  {
+    for ( auto cbf : connbuilder_factories_ )
+    {
+      delete cbf;
+    }
+    connbuilder_factories_.clear();
+    connruledict_->clear();
+  }
 }
 
 void
diff --git a/nestkernel/event_delivery_manager.cpp b/nestkernel/event_delivery_manager.cpp
index 1f3b94bee4..dbb98504d5 100644
--- a/nestkernel/event_delivery_manager.cpp
+++ b/nestkernel/event_delivery_manager.cpp
@@ -497,7 +497,7 @@ EventDeliveryManager::collocate_spike_data_buffers_( SendBufferPosition& send_bu
       ++num_spikes_per_rank[ rank ];
 
       // We do not break if condition is false, because there may be spikes that
-      // can be send to other ranks than the one that is full.
+      // can be sent to other ranks than the one that is full.
       if ( not send_buffer_position.is_chunk_filled( rank ) )
       {
         send_buffer[ send_buffer_position.idx( rank ) ] = emitted_spike.spike_data;
diff --git a/nestkernel/io_manager.cpp b/nestkernel/io_manager.cpp
index 9f9647d48f..2d6bdf27e5 100644
--- a/nestkernel/io_manager.cpp
+++ b/nestkernel/io_manager.cpp
@@ -61,27 +61,83 @@ namespace nest
 IOManager::IOManager()
   : overwrite_files_( false )
 {
-  register_recording_backend< RecordingBackendASCII >( "ascii" );
-  register_recording_backend< RecordingBackendMemory >( "memory" );
-  register_recording_backend< RecordingBackendScreen >( "screen" );
+}
+
+IOManager::~IOManager()
+{
+}
+
+void
+IOManager::initialize( const bool adjust_number_of_threads_or_rng_only )
+{
+  if ( not adjust_number_of_threads_or_rng_only )
+  {
+    // Register backends again, since finalize cleans up
+    // so backends from external modules are unloaded
+    register_recording_backend< RecordingBackendASCII >( "ascii" );
+    register_recording_backend< RecordingBackendMemory >( "memory" );
+    register_recording_backend< RecordingBackendScreen >( "screen" );
 #ifdef HAVE_MPI
-  register_recording_backend< RecordingBackendMPI >( "mpi" );
-  register_stimulation_backend< StimulationBackendMPI >( "mpi" );
+    register_recording_backend< RecordingBackendMPI >( "mpi" );
+    register_stimulation_backend< StimulationBackendMPI >( "mpi" );
 #endif
 #ifdef HAVE_SIONLIB
-  register_recording_backend< RecordingBackendSIONlib >( "sionlib" );
+    register_recording_backend< RecordingBackendSIONlib >( "sionlib" );
 #endif
+
+    DictionaryDatum dict( new Dictionary );
+    // The properties data_path and data_prefix can be set via environment variables
+    char* data_path = std::getenv( "NEST_DATA_PATH" );
+    if ( data_path )
+    {
+      ( *dict )[ names::data_path ] = std::string( data_path );
+    }
+    char* data_prefix = std::getenv( "NEST_DATA_PREFIX" );
+    if ( data_prefix )
+    {
+      ( *dict )[ names::data_prefix ] = std::string( data_prefix );
+    }
+
+    set_data_path_prefix_( dict );
+
+    overwrite_files_ = false;
+  }
+
+  for ( const auto& it : recording_backends_ )
+  {
+    it.second->initialize();
+  }
+  for ( const auto& it : stimulation_backends_ )
+  {
+    it.second->initialize();
+  }
 }
 
-IOManager::~IOManager()
+void
+IOManager::finalize( const bool adjust_number_of_threads_or_rng_only )
 {
-  for ( auto& it : recording_backends_ )
+  for ( const auto& it : recording_backends_ )
   {
-    delete it.second;
+    it.second->finalize();
   }
-  for ( auto& it : stimulation_backends_ )
+  for ( const auto& it : stimulation_backends_ )
+  {
+    it.second->finalize();
+  }
+
+  if ( not adjust_number_of_threads_or_rng_only )
   {
-    delete it.second;
+    for ( const auto& it : recording_backends_ )
+    {
+      delete it.second;
+    }
+    recording_backends_.clear();
+
+    for ( const auto& it : stimulation_backends_ )
+    {
+      delete it.second;
+    }
+    stimulation_backends_.clear();
   }
 }
 
@@ -131,52 +187,6 @@ IOManager::set_data_path_prefix_( const DictionaryDatum& dict )
   }
 }
 
-void
-IOManager::initialize( const bool adjust_number_of_threads_or_rng_only )
-{
-  if ( not adjust_number_of_threads_or_rng_only )
-  {
-    DictionaryDatum dict( new Dictionary );
-    // The properties data_path and data_prefix can be set via environment variables
-    char* data_path = std::getenv( "NEST_DATA_PATH" );
-    if ( data_path )
-    {
-      ( *dict )[ names::data_path ] = std::string( data_path );
-    }
-    char* data_prefix = std::getenv( "NEST_DATA_PREFIX" );
-    if ( data_prefix )
-    {
-      ( *dict )[ names::data_prefix ] = std::string( data_prefix );
-    }
-
-    set_data_path_prefix_( dict );
-
-    overwrite_files_ = false;
-  }
-
-  for ( const auto& it : recording_backends_ )
-  {
-    it.second->initialize();
-  }
-  for ( const auto& it : stimulation_backends_ )
-  {
-    it.second->initialize();
-  }
-}
-
-void
-IOManager::finalize( const bool )
-{
-  for ( const auto& it : recording_backends_ )
-  {
-    it.second->finalize();
-  }
-  for ( const auto& it : stimulation_backends_ )
-  {
-    it.second->finalize();
-  }
-}
-
 void
 IOManager::set_recording_backend_status( std::string recording_backend, const DictionaryDatum& d )
 {
diff --git a/nestkernel/kernel_manager.cpp b/nestkernel/kernel_manager.cpp
index 63b5937ada..2e407b249a 100644
--- a/nestkernel/kernel_manager.cpp
+++ b/nestkernel/kernel_manager.cpp
@@ -57,9 +57,9 @@ nest::KernelManager::KernelManager()
   , connection_manager()
   , sp_manager()
   , event_delivery_manager()
+  , io_manager()
   , model_manager()
   , music_manager()
-  , io_manager()
   , node_manager()
   , managers( { &logging_manager,
       &mpi_manager,
@@ -71,9 +71,9 @@ nest::KernelManager::KernelManager()
       &connection_manager,
       &sp_manager,
       &event_delivery_manager,
+      &io_manager,
       &model_manager,
       &music_manager,
-      &io_manager,
       &node_manager } )
   , initialized_( false )
 {
diff --git a/nestkernel/kernel_manager.h b/nestkernel/kernel_manager.h
index 78a31c52f3..216981b2b7 100644
--- a/nestkernel/kernel_manager.h
+++ b/nestkernel/kernel_manager.h
@@ -282,9 +282,9 @@ class KernelManager
   ConnectionManager connection_manager;
   SPManager sp_manager;
   EventDeliveryManager event_delivery_manager;
+  IOManager io_manager;
   ModelManager model_manager;
   MUSICManager music_manager;
-  IOManager io_manager;
   NodeManager node_manager;
   /**@}*/
 private:
diff --git a/nestkernel/nest_extension_interface.h b/nestkernel/nest_extension_interface.h
index e185504bc8..ff4d519a21 100644
--- a/nestkernel/nest_extension_interface.h
+++ b/nestkernel/nest_extension_interface.h
@@ -38,6 +38,7 @@
 #include "nest.h"
 #include "nest_impl.h"
 #include "nestmodule.h"
+#include "sp_manager_impl.h"
 #include "target_identifier.h"
 
 // C++ includes
diff --git a/nestkernel/nestmodule.cpp b/nestkernel/nestmodule.cpp
index bf0675f3d2..639f886077 100644
--- a/nestkernel/nestmodule.cpp
+++ b/nestkernel/nestmodule.cpp
@@ -30,9 +30,7 @@
 
 // Includes from nestkernel:
 #include "conn_builder.h"
-#include "conn_builder_conngen.h"
 #include "connection_creator_impl.h"
-#include "connection_manager_impl.h"
 #include "free_layer.h"
 #include "genericmodel.h"
 #include "grid_layer.h"
@@ -48,7 +46,6 @@
 #include "nest_types.h"
 #include "node.h"
 #include "parameter.h"
-#include "sp_manager_impl.h"
 #include "spatial.h"
 
 // Includes from sli:
@@ -2211,27 +2208,6 @@ NestModule::init( SLIInterpreter* i )
   i->createcommand( "cvdict_M", &cvdict_Mfunction );
   i->createcommand( "SelectNodesByMask_g_a_M", &selectnodesbymask_g_a_Mfunction );
 
-
-  // Add connection rules
-  kernel().connection_manager.register_conn_builder< OneToOneBuilder >( "one_to_one" );
-  kernel().connection_manager.register_conn_builder< AllToAllBuilder >( "all_to_all" );
-  kernel().connection_manager.register_conn_builder< FixedInDegreeBuilder >( "fixed_indegree" );
-  kernel().connection_manager.register_conn_builder< FixedOutDegreeBuilder >( "fixed_outdegree" );
-  kernel().connection_manager.register_conn_builder< BernoulliBuilder >( "pairwise_bernoulli" );
-  kernel().connection_manager.register_conn_builder< PoissonBuilder >( "pairwise_poisson" );
-  kernel().connection_manager.register_conn_builder< TripartiteBernoulliWithPoolBuilder >(
-    "tripartite_bernoulli_with_pool" );
-  kernel().connection_manager.register_conn_builder< SymmetricBernoulliBuilder >( "symmetric_pairwise_bernoulli" );
-  kernel().connection_manager.register_conn_builder< FixedTotalNumberBuilder >( "fixed_total_number" );
-#ifdef HAVE_LIBNEUROSIM
-  kernel().connection_manager.register_conn_builder< ConnectionGeneratorBuilder >( "conngen" );
-#endif
-
-  // Add MSP growth curves
-  kernel().sp_manager.register_growth_curve< GrowthCurveSigmoid >( "sigmoid" );
-  kernel().sp_manager.register_growth_curve< GrowthCurveGaussian >( "gaussian" );
-  kernel().sp_manager.register_growth_curve< GrowthCurveLinear >( "linear" );
-
   Token statusd = i->baselookup( Name( "statusdict" ) );
   DictionaryDatum dd = getValue< DictionaryDatum >( statusd );
   dd->insert( Name( "kernelname" ), new StringDatum( "NEST" ) );
diff --git a/nestkernel/sp_manager.cpp b/nestkernel/sp_manager.cpp
index 52e1f73d29..fb912b1f84 100644
--- a/nestkernel/sp_manager.cpp
+++ b/nestkernel/sp_manager.cpp
@@ -32,6 +32,7 @@
 #include "connector_model.h"
 #include "kernel_manager.h"
 #include "nest_names.h"
+#include "sp_manager_impl.h"
 
 namespace nest
 {
@@ -53,9 +54,12 @@ SPManager::~SPManager()
 void
 SPManager::initialize( const bool adjust_number_of_threads_or_rng_only )
 {
-  if ( adjust_number_of_threads_or_rng_only )
+  if ( not adjust_number_of_threads_or_rng_only )
   {
-    return;
+    // Add MSP growth curves
+    register_growth_curve< GrowthCurveSigmoid >( "sigmoid" );
+    register_growth_curve< GrowthCurveGaussian >( "gaussian" );
+    register_growth_curve< GrowthCurveLinear >( "linear" );
   }
 
   structural_plasticity_update_interval_ = 10000.;
@@ -63,13 +67,23 @@ SPManager::initialize( const bool adjust_number_of_threads_or_rng_only )
 }
 
 void
-SPManager::finalize( const bool )
+SPManager::finalize( const bool adjust_number_of_threads_or_rng_only )
 {
-  for ( std::vector< SPBuilder* >::const_iterator i = sp_conn_builders_.begin(); i != sp_conn_builders_.end(); i++ )
+  if ( not adjust_number_of_threads_or_rng_only )
   {
-    delete *i;
+    for ( auto spcb : sp_conn_builders_ )
+    {
+      delete spcb;
+    }
+    sp_conn_builders_.clear();
+
+    for ( auto gcf : growthcurve_factories_ )
+    {
+      delete gcf;
+    }
+    growthcurve_factories_.clear();
+    growthcurvedict_->clear();
   }
-  sp_conn_builders_.clear();
 }
 
 void