diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/__init__.py b/src/blenderbim/blenderbim/bim/module/aggregate/__init__.py
index bd7f6946ea..6c6dd30226 100644
--- a/src/blenderbim/blenderbim/bim/module/aggregate/__init__.py
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/__init__.py
@@ -17,20 +17,21 @@
 # along with BlenderBIM Add-on.  If not, see <http://www.gnu.org/licenses/>.
 
 import bpy
-from . import ui, operator
+from . import ui, prop, operator
 
 classes = (
     operator.AssignObject,
     operator.EnableEditingAggregate,
     operator.DisableEditingAggregate,
     operator.AddAggregate,
+    prop.BIMObjectAggregateProperties,
     ui.BIM_PT_aggregate,
 )
 
 
 def register():
-    pass
+    bpy.types.Object.BIMObjectAggregateProperties = bpy.props.PointerProperty(type=prop.BIMObjectAggregateProperties)
 
 
 def unregister():
-    pass
+    del bpy.types.Object.BIMObjectAggregateProperties
diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/data.py b/src/blenderbim/blenderbim/bim/module/aggregate/data.py
new file mode 100644
index 0000000000..4ae27e5ae4
--- /dev/null
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/data.py
@@ -0,0 +1,27 @@
+import bpy
+import blenderbim.tool as tool
+import ifcopenshell.util.element
+
+
+def refresh():
+    AggregateData.is_loaded = False
+
+
+class AggregateData:
+    data = {}
+    is_loaded = False
+
+    @classmethod
+    def load(cls):
+        cls.data = {"has_aggregate": cls.has_aggregate(), "label": cls.get_label()}
+        cls.is_loaded = True
+
+    @classmethod
+    def has_aggregate(cls):
+        return ifcopenshell.util.element.get_aggregate(tool.Ifc.get_entity(bpy.context.active_object))
+
+    @classmethod
+    def get_label(cls):
+        aggregate = ifcopenshell.util.element.get_aggregate(tool.Ifc.get_entity(bpy.context.active_object))
+        if aggregate:
+            return f"{aggregate.is_a()}/{aggregate.Name or ''}"
diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/operator.py b/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
index b9b830df3b..9a43886430 100644
--- a/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
@@ -17,89 +17,52 @@
 # along with BlenderBIM Add-on.  If not, see <http://www.gnu.org/licenses/>.
 
 import bpy
-import ifcopenshell.api
+import blenderbim.tool as tool
+import blenderbim.core.aggregate as core
+import blenderbim.bim.handler
 from blenderbim.bim.ifc import IfcStore
-from ifcopenshell.api.aggregate.data import Data
 
 
-class AssignObject(bpy.types.Operator):
+class Operator:
+    def execute(self, context):
+        IfcStore.execute_ifc_operator(self, context)
+        blenderbim.bim.handler.refresh_ui_data()
+        return {"FINISHED"}
+
+
+class AssignObject(bpy.types.Operator, Operator):
     bl_idname = "bim.assign_object"
     bl_label = "Assign Object"
     bl_options = {"REGISTER", "UNDO"}
-    relating_object: bpy.props.StringProperty()
-    related_object: bpy.props.StringProperty()
-
-    def execute(self, context):
-        return IfcStore.execute_ifc_operator(self, context)
+    relating_object: bpy.props.IntProperty()
+    related_object: bpy.props.IntProperty()
 
     def _execute(self, context):
-        self.file = IfcStore.get_file()
-        related_objects = (
-            [bpy.data.objects.get(self.related_object)] if self.related_object else context.selected_objects
+        core.assign_object(
+            tool.Ifc,
+            tool.Aggregator,
+            tool.Collector,
+            relating_obj=tool.Ifc.get_object(tool.Ifc.get().by_id(self.relating_object)),
+            related_obj=tool.Ifc.get_object(tool.Ifc.get().by_id(self.related_object)),
         )
-        relating_object = bpy.data.objects.get(self.relating_object)
-        if not relating_object or not relating_object.BIMObjectProperties.ifc_definition_id:
-            return {"FINISHED"}
-        for related_object in related_objects:
-            oprops = related_object.BIMObjectProperties
-            product = self.file.by_id(oprops.ifc_definition_id)
-            ifcopenshell.api.run(
-                "aggregate.assign_object",
-                self.file,
-                **{
-                    "product": product,
-                    "relating_object": self.file.by_id(relating_object.BIMObjectProperties.ifc_definition_id),
-                },
-            )
-            bpy.ops.bim.edit_object_placement(obj=related_object.name)
-            Data.load(IfcStore.get_file(), oprops.ifc_definition_id)
-            bpy.ops.bim.disable_editing_aggregate(obj=related_object.name)
-
-            spatial_collection = bpy.data.collections.get(related_object.name)
-            relating_collection = bpy.data.collections.get(relating_object.name)
-            if spatial_collection:
-                self.remove_collection(context.scene.collection, spatial_collection)
-                for collection in bpy.data.collections:
-                    if collection == relating_collection:
-                        if not collection.children.get(spatial_collection.name):
-                            collection.children.link(spatial_collection)
-                        continue
-                    self.remove_collection(collection, spatial_collection)
-            else:
-                for collection in related_object.users_collection:
-                    if collection.name.startswith("Ifc"):
-                        collection.objects.unlink(related_object)
-                relating_collection.objects.link(related_object)
-        return {"FINISHED"}
-
-    def remove_collection(self, parent, child):
-        try:
-            parent.children.unlink(child)
-        except:
-            pass
 
 
-class EnableEditingAggregate(bpy.types.Operator):
+class EnableEditingAggregate(bpy.types.Operator, Operator):
     bl_idname = "bim.enable_editing_aggregate"
     bl_label = "Enable Editing Aggregate"
     bl_options = {"REGISTER", "UNDO"}
 
-    def execute(self, context):
-        context.active_object.BIMObjectProperties.relating_object = None
-        context.active_object.BIMObjectProperties.is_editing_aggregate = True
-        return {"FINISHED"}
+    def _execute(self, context):
+        core.enable_editing_aggregate(tool.Aggregator, obj=context.active_object)
 
 
-class DisableEditingAggregate(bpy.types.Operator):
+class DisableEditingAggregate(bpy.types.Operator, Operator):
     bl_idname = "bim.disable_editing_aggregate"
     bl_label = "Disable Editing Aggregate"
-    obj: bpy.props.StringProperty()
     bl_options = {"REGISTER", "UNDO"}
 
-    def execute(self, context):
-        obj = bpy.data.objects.get(self.obj) if self.obj else context.active_object
-        obj.BIMObjectProperties.is_editing_aggregate = False
-        return {"FINISHED"}
+    def _execute(self, context):
+        core.disable_editing_aggregate(tool.Aggregator, obj=context.active_object)
 
 
 class AddAggregate(bpy.types.Operator):
diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/prop.py b/src/blenderbim/blenderbim/bim/module/aggregate/prop.py
new file mode 100644
index 0000000000..8ecb77aeec
--- /dev/null
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/prop.py
@@ -0,0 +1,19 @@
+import bpy
+from blenderbim.bim.prop import StrProperty, Attribute
+from blenderbim.bim.module.spatial.data import SpatialData
+from bpy.types import PropertyGroup
+from bpy.props import (
+    PointerProperty,
+    StringProperty,
+    EnumProperty,
+    BoolProperty,
+    IntProperty,
+    FloatProperty,
+    FloatVectorProperty,
+    CollectionProperty,
+)
+
+
+class BIMObjectAggregateProperties(PropertyGroup):
+    is_editing: BoolProperty(name="Is Editing")
+    relating_object: PointerProperty(name="Aggregate", type=bpy.types.Object)
diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/ui.py b/src/blenderbim/blenderbim/bim/module/aggregate/ui.py
index eaa201c8cf..e107784bcb 100644
--- a/src/blenderbim/blenderbim/bim/module/aggregate/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/ui.py
@@ -17,7 +17,7 @@
 # along with BlenderBIM Add-on.  If not, see <http://www.gnu.org/licenses/>.
 
 from bpy.types import Panel
-from ifcopenshell.api.aggregate.data import Data
+from blenderbim.bim.module.aggregate.data import AggregateData
 from blenderbim.bim.ifc import IfcStore
 
 
@@ -40,34 +40,27 @@ class BIM_PT_aggregate(Panel):
             return False
         if not IfcStore.get_file().by_id(props.ifc_definition_id).is_a("IfcObjectDefinition"):
             return False
-        if props.ifc_definition_id not in Data.products:
-            Data.load(IfcStore.get_file(), props.ifc_definition_id)
-        if not Data.products[props.ifc_definition_id]:
-            return False
         return True
 
     def draw(self, context):
-        props = context.active_object.BIMObjectProperties
-        if not props.ifc_definition_id:
-            return
-        if props.ifc_definition_id not in Data.products:
-            Data.load(IfcStore.get_file(), props.ifc_definition_id)
+        if not AggregateData.is_loaded:
+            AggregateData.load()
 
-        if props.is_editing_aggregate:
+        props = context.active_object.BIMObjectAggregateProperties
+
+        if props.is_editing:
             row = self.layout.row(align=True)
             row.prop(props, "relating_object", text="")
             if props.relating_object:
-                row.operator(
-                    "bim.assign_object", icon="CHECKMARK", text=""
-                ).relating_object = props.relating_object.name
+                op = row.operator("bim.assign_object", icon="CHECKMARK", text="")
+                op.relating_object = props.relating_object.BIMObjectProperties.ifc_definition_id
+                op.related_object = context.active_object.BIMObjectProperties.ifc_definition_id
             row.operator("bim.disable_editing_aggregate", icon="CANCEL", text="")
         else:
             row = self.layout.row(align=True)
-            name = "{}/{}".format(
-                Data.products[props.ifc_definition_id]["type"], Data.products[props.ifc_definition_id]["Name"]
-            )
-            if name == "None/None":
-                name = "No Aggregate Found"
-            row.label(text=name)
+            if AggregateData.data["has_aggregate"]:
+                row.label(text=AggregateData.data["label"])
+            else:
+                row.label(text="No Aggregate Found")
             row.operator("bim.enable_editing_aggregate", icon="GREASEPENCIL", text="")
             row.operator("bim.add_aggregate", icon="ADD", text="")
diff --git a/src/blenderbim/blenderbim/bim/module/project/operator.py b/src/blenderbim/blenderbim/bim/module/project/operator.py
index ac13623bc6..b2b5decfc2 100644
--- a/src/blenderbim/blenderbim/bim/module/project/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/project/operator.py
@@ -94,9 +94,16 @@ class CreateProject(bpy.types.Operator):
         bpy.ops.bim.assign_class(obj=site.name, ifc_class="IfcSite")
         bpy.ops.bim.assign_class(obj=building.name, ifc_class="IfcBuilding")
         bpy.ops.bim.assign_class(obj=building_storey.name, ifc_class="IfcBuildingStorey")
-        bpy.ops.bim.assign_object(related_object=site.name, relating_object=project.name)
-        bpy.ops.bim.assign_object(related_object=building.name, relating_object=site.name)
-        bpy.ops.bim.assign_object(related_object=building_storey.name, relating_object=building.name)
+
+        blenderbim.core.aggregate.assign_object(
+            tool.Ifc, tool.Aggregator, tool.Collector, relating_obj=project, related_obj=site
+        )
+        blenderbim.core.aggregate.assign_object(
+            tool.Ifc, tool.Aggregator, tool.Collector, relating_obj=site, related_obj=building
+        )
+        blenderbim.core.aggregate.assign_object(
+            tool.Ifc, tool.Aggregator, tool.Collector, relating_obj=building, related_obj=building_storey
+        )
 
         context.view_layer.objects.active = active_object
         return {"FINISHED"}
diff --git a/src/blenderbim/blenderbim/bim/module/spatial/data.py b/src/blenderbim/blenderbim/bim/module/spatial/data.py
index b9e099ce92..4eac3aefc0 100644
--- a/src/blenderbim/blenderbim/bim/module/spatial/data.py
+++ b/src/blenderbim/blenderbim/bim/module/spatial/data.py
@@ -32,10 +32,7 @@ class SpatialData:
     @classmethod
     def load(cls):
         cls.data = {
-            "is_editing": bpy.context.active_object.BIMObjectSpatialProperties.is_editing,
             "parent_container_id": cls.get_parent_container_id(),
-            "container_id": cls.get_container_id(),
-            "container_list_settings": cls.get_container_list_settings(),
             "is_contained": cls.is_contained(),
             "is_directly_contained": cls.is_directly_contained(),
             "label": cls.get_label(),
@@ -52,19 +49,6 @@ class SpatialData:
             return
         return container.Decomposes[0].RelatingObject.id()
 
-    @classmethod
-    def get_container_id(cls):
-        props = bpy.context.scene.BIMSpatialProperties
-        try:
-            return props.containers[props.active_container_index].ifc_definition_id
-        except:
-            return 0
-
-    @classmethod
-    def get_container_list_settings(cls):
-        props = bpy.context.scene.BIMSpatialProperties
-        return ["", props, "containers", props, "active_container_id"]
-
     @classmethod
     def is_contained(cls):
         return ifcopenshell.util.element.get_container(tool.Ifc.get_entity(bpy.context.active_object))
diff --git a/src/blenderbim/blenderbim/bim/module/spatial/prop.py b/src/blenderbim/blenderbim/bim/module/spatial/prop.py
index 4e15dff8ab..6dbecb6120 100644
--- a/src/blenderbim/blenderbim/bim/module/spatial/prop.py
+++ b/src/blenderbim/blenderbim/bim/module/spatial/prop.py
@@ -32,10 +32,6 @@ from bpy.props import (
 )
 
 
-def update_active_container_index(self, context):
-    SpatialData.is_loaded = False
-
-
 class SpatialElement(PropertyGroup):
     name: StringProperty(name="Name")
     long_name: StringProperty(name="Long Name")
@@ -46,7 +42,7 @@ class SpatialElement(PropertyGroup):
 
 class BIMSpatialProperties(PropertyGroup):
     containers: CollectionProperty(name="Containers", type=SpatialElement)
-    active_container_index: IntProperty(name="Active Container Index", update=update_active_container_index)
+    active_container_index: IntProperty(name="Active Container Index")
     active_container_id: IntProperty(name="Active Container Id")
 
 
diff --git a/src/blenderbim/blenderbim/bim/module/spatial/ui.py b/src/blenderbim/blenderbim/bim/module/spatial/ui.py
index 9304528af6..94aea9bab3 100644
--- a/src/blenderbim/blenderbim/bim/module/spatial/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/spatial/ui.py
@@ -18,7 +18,6 @@
 
 from bpy.types import Panel, UIList
 from blenderbim.bim.ifc import IfcStore
-from ifcopenshell.api.spatial.data import Data
 from blenderbim.bim.module.spatial.data import SpatialData
 
 
@@ -38,26 +37,26 @@ class BIM_PT_spatial(Panel):
             return False
         if not IfcStore.get_element(oprops.ifc_definition_id):
             return False
-        if oprops.ifc_definition_id not in Data.products:
-            Data.load(IfcStore.get_file(), oprops.ifc_definition_id)
-        if not Data.products[oprops.ifc_definition_id]:
-            return False
         return True
 
     def draw(self, context):
         if not SpatialData.is_loaded:
             SpatialData.load()
 
-        if SpatialData.data["is_editing"]:
+        props = context.scene.BIMSpatialProperties
+        osprops = context.active_object.BIMObjectSpatialProperties
+
+        if osprops.is_editing:
             row = self.layout.row(align=True)
             if SpatialData.data["parent_container_id"]:
                 op = row.operator("bim.change_spatial_level", text="", icon="FRAME_PREV")
                 op.parent = SpatialData.data["parent_container_id"]
-            row.operator("bim.assign_container", icon="CHECKMARK").structure = SpatialData.data["container_id"]
+            op = row.operator("bim.assign_container", icon="CHECKMARK")
+            op.structure = props.containers[props.active_container_index].ifc_definition_id
             row.operator("bim.copy_to_container", icon="COPYDOWN", text="")
             row.operator("bim.disable_editing_container", icon="CANCEL", text="")
 
-            self.layout.template_list("BIM_UL_containers", *SpatialData.data["container_list_settings"])
+            self.layout.template_list("BIM_UL_containers", "", props, "containers", props, "active_container_id")
         else:
             row = self.layout.row(align=True)
             if SpatialData.data["is_contained"]:
diff --git a/src/blenderbim/blenderbim/bim/prop.py b/src/blenderbim/blenderbim/bim/prop.py
index fd6ee6ec99..fd65f955c8 100644
--- a/src/blenderbim/blenderbim/bim/prop.py
+++ b/src/blenderbim/blenderbim/bim/prop.py
@@ -267,8 +267,6 @@ class BIMObjectProperties(PropertyGroup):
     )
     is_reassigning_class: BoolProperty(name="Is Reassigning Class")
     global_ids: CollectionProperty(name="GlobalIds", type=GlobalId)
-    relating_object: PointerProperty(name="Aggregate", type=bpy.types.Object)
-    is_editing_aggregate: BoolProperty(name="Is Editing Aggregate")
     psets: CollectionProperty(name="Psets", type=PsetQto)
     qtos: CollectionProperty(name="Qtos", type=PsetQto)
 
diff --git a/src/blenderbim/blenderbim/core/aggregate.py b/src/blenderbim/blenderbim/core/aggregate.py
new file mode 100644
index 0000000000..3f1e817db1
--- /dev/null
+++ b/src/blenderbim/blenderbim/core/aggregate.py
@@ -0,0 +1,18 @@
+def enable_editing_aggregate(aggregator, obj=None):
+    aggregator.enable_editing(obj)
+
+
+def disable_editing_aggregate(aggregator, obj=None):
+    aggregator.disable_editing(obj)
+
+
+def assign_object(ifc, aggregator, collector, relating_obj=None, related_obj=None):
+    if not aggregator.can_aggregate(relating_obj, related_obj):
+        return
+    rel = ifc.run(
+        "aggregate.assign_object", product=ifc.get_entity(related_obj), relating_object=ifc.get_entity(relating_obj)
+    )
+    collector.assign(relating_obj)
+    collector.assign(related_obj)
+    aggregator.disable_editing(related_obj)
+    return rel
diff --git a/src/blenderbim/blenderbim/core/tool.py b/src/blenderbim/blenderbim/core/tool.py
index 9c5182e648..a4ce6931c8 100644
--- a/src/blenderbim/blenderbim/core/tool.py
+++ b/src/blenderbim/blenderbim/core/tool.py
@@ -56,6 +56,23 @@ class AddressEditor(abc.ABC):
         pass
 
 
+class Aggregator(abc.ABC):
+    @classmethod
+    @abc.abstractmethod
+    def enable_editing(cls, obj):
+        pass
+
+    @classmethod
+    @abc.abstractmethod
+    def disable_editing(cls, obj):
+        pass
+
+    @classmethod
+    @abc.abstractmethod
+    def can_aggregate(cls, relating_object, related_object):
+        pass
+
+
 class Blender(abc.ABC):
     pass
 
diff --git a/src/blenderbim/blenderbim/tool/__init__.py b/src/blenderbim/blenderbim/tool/__init__.py
index 9d04e812d1..2b081b3416 100644
--- a/src/blenderbim/blenderbim/tool/__init__.py
+++ b/src/blenderbim/blenderbim/tool/__init__.py
@@ -17,6 +17,7 @@
 # along with BlenderBIM Add-on.  If not, see <http://www.gnu.org/licenses/>.
 
 from blenderbim.tool.address_editor import AddressEditor
+from blenderbim.tool.aggregator import Aggregator
 from blenderbim.tool.blender import Blender
 from blenderbim.tool.collector import Collector
 from blenderbim.tool.container import Container
diff --git a/src/blenderbim/blenderbim/tool/aggregator.py b/src/blenderbim/blenderbim/tool/aggregator.py
new file mode 100644
index 0000000000..a114b33adb
--- /dev/null
+++ b/src/blenderbim/blenderbim/tool/aggregator.py
@@ -0,0 +1,34 @@
+import blenderbim.core.tool
+import blenderbim.tool as tool
+
+
+class Aggregator(blenderbim.core.tool.Aggregator):
+    @classmethod
+    def enable_editing(cls, obj):
+        obj.BIMObjectAggregateProperties.is_editing = True
+
+    @classmethod
+    def disable_editing(cls, obj):
+        obj.BIMObjectAggregateProperties.is_editing = False
+
+    @classmethod
+    def can_aggregate(cls, relating_obj, related_obj):
+        relating_object = tool.Ifc.get_entity(relating_obj)
+        related_object = tool.Ifc.get_entity(related_obj)
+        if not relating_object or not related_object:
+            return False
+        if relating_object.is_a("IfcElement") and related_object.is_a("IfcElement"):
+            if relating_obj.data:
+                return False
+            return True
+        if tool.Ifc.get_schema() == "IFC2X3":
+            if relating_object.is_a("IfcSpatialStructureElement") and related_object.is_a("IfcSpatialStructureElement"):
+                return True
+            if relating_object.is_a("IfcProject") and related_object.is_a("IfcSpatialStructureElement"):
+                return True
+        else:
+            if relating_object.is_a("IfcSpatialElement") and related_object.is_a("IfcSpatialElement"):
+                return True
+            if relating_object.is_a("IfcProject") and related_object.is_a("IfcSpatialElement"):
+                return True
+        return False
diff --git a/src/blenderbim/blenderbim/tool/collector.py b/src/blenderbim/blenderbim/tool/collector.py
index cdbf6fdfd8..48cf7120c9 100644
--- a/src/blenderbim/blenderbim/tool/collector.py
+++ b/src/blenderbim/blenderbim/tool/collector.py
@@ -26,29 +26,76 @@ import blenderbim.tool as tool
 class Collector(blenderbim.core.tool.Collector):
     @classmethod
     def assign(cls, obj):
-        for collection in obj.users_collection:
-            collection.objects.unlink(obj)
-
         element = tool.Ifc.get_entity(obj)
+
+        object_collection = None
+        collection_collection = None
+
+        object_collection = cls._get_own_collection(element, obj)
+        if object_collection:
+            collection_collection = cls._get_collection(element, obj)
+        else:
+            object_collection = cls._get_collection(element, obj)
+
+        if obj.users_collection != (object_collection,):
+            for collection in obj.users_collection:
+                collection.objects.unlink(obj)
+            object_collection.objects.link(obj)
+
+        if collection_collection and collection_collection.children.find(object_collection.name) == -1:
+            for collection in bpy.data.collections:
+                if collection.children.find(object_collection.name) != -1:
+                    collection.children.unlink(object_collection)
+            collection_collection.children.link(object_collection)
+
+    @classmethod
+    def _get_own_collection(cls, element, obj):
+        if element.is_a("IfcProject"):
+            collection = bpy.data.collections.get(obj.name)
+            if not collection:
+                collection = bpy.data.collections.new(obj.name)
+            return collection
+
+        if tool.Ifc.get_schema() == "IFC2X3":
+            if element.is_a("IfcSpatialStructureElement"):
+                collection = bpy.data.collections.get(obj.name)
+                if not collection:
+                    collection = bpy.data.collections.new(obj.name)
+                return collection
+        else:
+            if element.is_a("IfcSpatialElement"):
+                collection = bpy.data.collections.get(obj.name)
+                if not collection:
+                    collection = bpy.data.collections.new(obj.name)
+                return collection
+
+        if element.IsDecomposedBy:
+            collection = bpy.data.collections.get(obj.name)
+            if not collection:
+                collection = bpy.data.collections.new(obj.name)
+            return collection
+
+    @classmethod
+    def _get_collection(cls, element, obj):
         aggregate = ifcopenshell.util.element.get_aggregate(element)
         if aggregate:
             aggregate_obj = tool.Ifc.get_object(aggregate)
             collection = bpy.data.collections.get(aggregate_obj.name)
             if collection:
-                collection.objects.link(obj)
-                return
+                return collection
 
         container = ifcopenshell.util.element.get_container(element)
         if container:
             container_obj = tool.Ifc.get_object(container)
             collection = bpy.data.collections.get(container_obj.name)
             if collection:
-                collection.objects.link(obj)
-                return
+                return collection
+
+        if element.is_a("IfcProject"):
+            return bpy.context.scene.collection
 
         project_obj = tool.Ifc.get_object(tool.Ifc.get().by_type("IfcProject")[0])
         if project_obj:
             collection = bpy.data.collections.get(project_obj.name)
             if collection:
-                collection.objects.link(obj)
-                return
+                return collection
diff --git a/src/blenderbim/test/bim/feature/aggregate.feature b/src/blenderbim/test/bim/feature/aggregate.feature
new file mode 100644
index 0000000000..8a0f3b9141
--- /dev/null
+++ b/src/blenderbim/test/bim/feature/aggregate.feature
@@ -0,0 +1,28 @@
+@aggregate
+Feature: Aggregate
+    Covers element and spatial aggregation
+
+Scenario: Enable editing aggregate
+    Given an empty IFC project
+    And the object "IfcSite/My Site" is selected
+    When I press "bim.enable_editing_aggregate"
+    Then nothing happens
+
+Scenario: Disable editing aggregate
+    Given an empty IFC project
+    And the object "IfcSite/My Site" is selected
+    And I press "bim.enable_editing_aggregate"
+    When I press "bim.disable_editing_aggregate"
+    Then nothing happens
+
+Scenario: Assign object
+    Given an empty IFC project
+    And the object "IfcSite/My Site" is selected
+    And I press "bim.enable_editing_aggregate"
+    And the variable "relating_object" is "tool.Ifc.get().by_type('IfcSite')[0].id()"
+    And the variable "related_object" is "tool.Ifc.get().by_type('IfcBuildingStorey')[0].id()"
+    When I press "bim.assign_object(relating_object={relating_object}, related_object={related_object})"
+    Then the object "IfcSite/My Site" is in the collection "IfcSite/My Site"
+    Then the object "IfcBuildingStorey/My Storey" is in the collection "IfcBuildingStorey/My Storey"
+    Then the collection "IfcBuildingStorey/My Storey" is in the collection "IfcSite/My Site"
+
diff --git a/src/blenderbim/test/bim/test_feature.py b/src/blenderbim/test/bim/test_feature.py
index dd6424646a..a7700a5df2 100644
--- a/src/blenderbim/test/bim/test_feature.py
+++ b/src/blenderbim/test/bim/test_feature.py
@@ -262,3 +262,8 @@ def prop_is_value(prop, value):
 @then(parsers.parse('the object "{name}" is in the collection "{collection}"'))
 def the_object_name_is_in_the_collection_collection(name, collection):
     assert collection in [c.name for c in the_object_name_exists(name).users_collection]
+
+
+@then(parsers.parse('the collection "{name1}" is in the collection "{name2}"'))
+def the_collection_name1_is_in_the_collection_name2(name1, name2):
+    assert bpy.data.collections.get(name2).children.get(name1)
diff --git a/src/blenderbim/test/core/bootstrap.py b/src/blenderbim/test/core/bootstrap.py
index 7b9a94d2b7..c8edfebabb 100644
--- a/src/blenderbim/test/core/bootstrap.py
+++ b/src/blenderbim/test/core/bootstrap.py
@@ -35,6 +35,13 @@ def blender():
     prophet.verify()
 
 
+@pytest.fixture
+def aggregator():
+    prophet = Prophecy(blenderbim.core.tool.Aggregator)
+    yield prophet
+    prophet.verify()
+
+
 @pytest.fixture
 def person_editor():
     prophet = Prophecy(blenderbim.core.tool.PersonEditor)
diff --git a/src/blenderbim/test/core/test_aggregate.py b/src/blenderbim/test/core/test_aggregate.py
new file mode 100644
index 0000000000..f7f82bc5cb
--- /dev/null
+++ b/src/blenderbim/test/core/test_aggregate.py
@@ -0,0 +1,31 @@
+import blenderbim.core.aggregate as subject
+from test.core.bootstrap import ifc, aggregator, collector
+
+
+class TestEnableEditingAggregate:
+    def test_run(self, aggregator):
+        aggregator.enable_editing("obj").should_be_called()
+        subject.enable_editing_aggregate(aggregator, obj="obj")
+
+
+class TestDisableEditingAggregate:
+    def test_run(self, aggregator):
+        aggregator.disable_editing("obj").should_be_called()
+        subject.disable_editing_aggregate(aggregator, obj="obj")
+
+
+class TestAssignObject:
+    def test_run(self, ifc, aggregator, collector):
+        aggregator.can_aggregate("relating_obj", "related_obj").should_be_called().will_return(True)
+        ifc.get_entity("relating_obj").should_be_called().will_return("relating_object")
+        ifc.get_entity("related_obj").should_be_called().will_return("related_object")
+        ifc.run(
+            "aggregate.assign_object", product="related_object", relating_object="relating_object"
+        ).should_be_called().will_return("rel")
+        aggregator.disable_editing("related_obj").should_be_called()
+        collector.assign("relating_obj").should_be_called()
+        collector.assign("related_obj").should_be_called()
+        assert (
+            subject.assign_object(ifc, aggregator, collector, relating_obj="relating_obj", related_obj="related_obj")
+            == "rel"
+        )
diff --git a/src/blenderbim/test/tool/test_aggregator.py b/src/blenderbim/test/tool/test_aggregator.py
new file mode 100644
index 0000000000..92ee92ebe0
--- /dev/null
+++ b/src/blenderbim/test/tool/test_aggregator.py
@@ -0,0 +1,101 @@
+import bpy
+import ifcopenshell
+import blenderbim.core.tool
+import blenderbim.tool as tool
+from test.bim.bootstrap import NewFile
+from blenderbim.tool.aggregator import Aggregator as subject
+
+
+class TestImplementsTool(NewFile):
+    def test_run(self):
+        assert isinstance(subject(), blenderbim.core.tool.Aggregator)
+
+
+class TestEnableEditing(NewFile):
+    def test_run(self):
+        obj = bpy.data.objects.new("Object", None)
+        subject.enable_editing(obj)
+        assert obj.BIMObjectAggregateProperties.is_editing is True
+
+
+class TestDisableEditing(NewFile):
+    def test_run(self):
+        obj = bpy.data.objects.new("Object", None)
+        subject.enable_editing(obj)
+        subject.disable_editing(obj)
+        assert obj.BIMObjectAggregateProperties.is_editing is False
+
+
+class TestCanAggregate(NewFile):
+    def test_elements_can_aggregate(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        element = ifc.createIfcElementAssembly()
+        element_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(element, element_obj)
+        subelement = ifc.createIfcBeam()
+        subelement_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(subelement, subelement_obj)
+        assert subject.can_aggregate(element_obj, subelement_obj) is True
+
+    def test_spatial_elements_can_aggregate(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        element = ifc.createIfcSite()
+        element_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(element, element_obj)
+        subelement = ifc.createIfcBuilding()
+        subelement_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(subelement, subelement_obj)
+        assert subject.can_aggregate(element_obj, subelement_obj) is True
+
+    def test_spatial_elements_can_aggregate_2x3(self):
+        ifc = ifcopenshell.file(schema="IFC2X3")
+        tool.Ifc.set(ifc)
+        element = ifc.createIfcSite()
+        element_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(element, element_obj)
+        subelement = ifc.createIfcBuilding()
+        subelement_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(subelement, subelement_obj)
+        assert subject.can_aggregate(element_obj, subelement_obj) is True
+
+    def test_spatial_elements_and_projects_can_aggregate(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        element = ifc.createIfcProject()
+        element_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(element, element_obj)
+        subelement = ifc.createIfcBuilding()
+        subelement_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(subelement, subelement_obj)
+        assert subject.can_aggregate(element_obj, subelement_obj) is True
+
+    def test_spatial_elements_and_projects_can_aggregate_2x3(self):
+        ifc = ifcopenshell.file(schema="IFC2X3")
+        tool.Ifc.set(ifc)
+        element = ifc.createIfcProject()
+        element_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(element, element_obj)
+        subelement = ifc.createIfcBuilding()
+        subelement_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(subelement, subelement_obj)
+        assert subject.can_aggregate(element_obj, subelement_obj) is True
+
+    def test_unlinked_elements_cannot_aggregate(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        element_obj = bpy.data.objects.new("Object", None)
+        subelement_obj = bpy.data.objects.new("Object", None)
+        assert subject.can_aggregate(element_obj, subelement_obj) is False
+
+    def test_aggregates_with_meshes_are_invalid(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        element = ifc.createIfcElementAssembly()
+        element_obj = bpy.data.objects.new("Object", bpy.data.meshes.new("Mesh"))
+        tool.Ifc.link(element, element_obj)
+        subelement = ifc.createIfcBeam()
+        subelement_obj = bpy.data.objects.new("Object", None)
+        tool.Ifc.link(subelement, subelement_obj)
+        assert subject.can_aggregate(element_obj, subelement_obj) is False
diff --git a/src/blenderbim/test/tool/test_collector.py b/src/blenderbim/test/tool/test_collector.py
index cc565c0818..f94145c05e 100644
--- a/src/blenderbim/test/tool/test_collector.py
+++ b/src/blenderbim/test/tool/test_collector.py
@@ -55,3 +55,47 @@ class TestAssign(NewFile):
         subject.assign(wall_obj)
         assert len(wall_obj.users_collection) == 1
         assert "IfcProject" in wall_obj.users_collection[0].name
+
+    def test_in_decomposition_mode_spatial_elements_are_placed_in_a_collection_of_the_same_name(self):
+        bpy.ops.bim.create_project()
+        space_obj = bpy.data.objects.new("IfcSpace/Name", None)
+        space_element = tool.Ifc.get().createIfcSpace()
+        tool.Ifc.link(space_element, space_obj)
+        bpy.context.scene.collection.objects.link(space_obj)
+        ifcopenshell.api.run(
+            "aggregate.assign_object",
+            tool.Ifc.get(),
+            relating_object=tool.Ifc.get().by_type("IfcSite")[0],
+            product=space_element,
+        )
+        subject.assign(space_obj)
+        assert len(space_obj.users_collection) == 1
+        assert space_obj.users_collection[0].name == space_obj.name
+
+    def test_in_decomposition_mode_aggregates_are_placed_in_a_collection_of_the_same_name(self):
+        bpy.ops.bim.create_project()
+        element_obj = bpy.data.objects.new("IfcElementAssembly/Name", None)
+        element = tool.Ifc.get().createIfcElementAssembly()
+        subelement_obj = bpy.data.objects.new("IfcBeam/Name", None)
+        subelement = tool.Ifc.get().createIfcBeam()
+        tool.Ifc.link(element, element_obj)
+        bpy.context.scene.collection.objects.link(element_obj)
+        ifcopenshell.api.run(
+            "aggregate.assign_object",
+            tool.Ifc.get(),
+            relating_object=element,
+            product=subelement,
+        )
+        subject.assign(element_obj)
+        assert len(element_obj.users_collection) == 1
+        assert element_obj.users_collection[0].name == element_obj.name
+
+    def test_in_decomposition_mode_projects_are_placed_in_a_collection_of_the_same_name(self):
+        tool.Ifc.set(ifcopenshell.file())
+        element_obj = bpy.data.objects.new("IfcProject/Name", None)
+        element = tool.Ifc.get().createIfcProject()
+        tool.Ifc.link(element, element_obj)
+        bpy.context.scene.collection.objects.link(element_obj)
+        subject.assign(element_obj)
+        assert len(element_obj.users_collection) == 1
+        assert element_obj.users_collection[0].name == element_obj.name