diff --git a/src/ifcconvert/ColladaSerializer.cpp b/src/ifcconvert/ColladaSerializer.cpp
index 8fea20fa6e..2015e7791c 100644
--- a/src/ifcconvert/ColladaSerializer.cpp
+++ b/src/ifcconvert/ColladaSerializer.cpp
@@ -363,8 +363,8 @@ void ColladaSerializer::ColladaExporter::write(const IfcGeom::TriangulationEleme
 		material_references.push_back(material_name);
 	}
 
-	DeferredObject defered = (serializer->settings().get(SerializerSettings::USE_ELEMENT_HIERARCHY) ?
-		DeferredObject(name, representation_id, o->type(), o->transformation().matrix().data(), mesh.verts(), mesh.normals(),
+	DeferredObject defered = (serializer->settings().get(SerializerSettings::USE_ELEMENT_HIERARCHY) && o->storey() != NULL ?
+		DeferredObject(name, representation_id, o->type(), o->transformation().matrix().data(), mesh.verts(), mesh.normals(), 
 			mesh.faces(), mesh.edges(), mesh.material_ids(), mesh.materials(), material_references, mesh.uvs(), *(o->storey())) : 
 		DeferredObject(name, representation_id, o->type(), o->transformation().matrix().data(), mesh.verts(), mesh.normals(),
 				mesh.faces(), mesh.edges(), mesh.material_ids(), mesh.materials(), material_references, mesh.uvs()));
@@ -373,20 +373,30 @@ void ColladaSerializer::ColladaExporter::write(const IfcGeom::TriangulationEleme
 
 std::string ColladaSerializer::ColladaExporter::differentiateSlabTypes(const IfcGeom::TriangulationElement<real_t>* o) {
 	IfcSlab* slab = (IfcSlab*)o->product();
-	switch (slab->PredefinedType()){
-			case (IfcSlabTypeEnum::IfcSlabType_ROOF):
-				return "_Roof";
-				break;
-			case (IfcSlabTypeEnum::IfcSlabType_LANDING):
-				return "_Landing";
-				break;
-			case (IfcSlabTypeEnum::IfcSlabType_BASESLAB):
-				return "_BasesLab";
-				break;
-			default:
-				return "_Unknown";
-				break;
-		}
+	switch (slab->PredefinedType())
+	{
+		case (IfcSlabTypeEnum::IfcSlabType_FLOOR):
+			return "_Floor";
+			break;
+		case (IfcSlabTypeEnum::IfcSlabType_ROOF):
+			return "_Roof";
+			break;
+		case (IfcSlabTypeEnum::IfcSlabType_LANDING):
+			return "_Landing";
+			break;
+		case (IfcSlabTypeEnum::IfcSlabType_BASESLAB):
+			return "_BaseSlab";
+			break;
+		case (IfcSlabTypeEnum::IfcSlabType_USERDEFINED):
+			return "_" + slab->ObjectType();
+			break;
+		case (IfcSlabTypeEnum::IfcSlabType_NOTDEFINED):
+			return "_NotDefined";
+			break;
+		default:
+			return "_Unknown";
+			break;
+	}
 }
 
 void ColladaSerializer::ColladaExporter::endDocument() {
diff --git a/src/ifcconvert/ColladaSerializer.h b/src/ifcconvert/ColladaSerializer.h
index 15bf6f84b8..60fd39370f 100644
--- a/src/ifcconvert/ColladaSerializer.h
+++ b/src/ifcconvert/ColladaSerializer.h
@@ -127,17 +127,34 @@ private:
 		class DeferredObject {
 		friend bool operator < (const DeferredObject & def_obj1, const DeferredObject & def_obj2)
 		{
+			// Retrieve the parents of the objects to compare
 			const IfcGeom::Element<real_t>* parent1 = def_obj1.parent;
 			const IfcGeom::Element<real_t>* parent2 = def_obj2.parent;
 			
+			// If a parent is null
 			if (parent1 == NULL || parent2 == NULL)
 			{
-				bool res = (def_obj1.unique_id < def_obj2.unique_id ? true : false);
+				bool res = (parent1 == NULL) ? true : false;
 				return res;
 			}
+			// If both parent are not null
 			else
 			{
-				bool res = parent1->name() < parent2->name() ? true : false;
+				// Retrieve the IfcBuildingStorey
+				Ifc2x3::IfcBuildingStorey* storey1 = (Ifc2x3::IfcBuildingStorey*)parent1->product();
+				Ifc2x3::IfcBuildingStorey* storey2 = (Ifc2x3::IfcBuildingStorey*)parent2->product();
+
+				bool res = true;
+
+				// Check if the storeys both have an elevation value
+				if (storey1->hasElevation() && storey2->hasElevation())
+				{
+					// Use the elevation in order to sort
+					res = storey1->Elevation() > storey2->Elevation() ? true : false;
+				}
+				// If the evelations are not set, use the names to sort
+				else { res = parent1->name().compare(parent2->name()) > 0 ? true : false; }
+				
 				return res;
 			}
 		}
diff --git a/src/ifcgeom/IfcGeomIterator.h b/src/ifcgeom/IfcGeomIterator.h
index 8b90046e69..223704bb6a 100644
--- a/src/ifcgeom/IfcGeomIterator.h
+++ b/src/ifcgeom/IfcGeomIterator.h
@@ -604,6 +604,7 @@ namespace IfcGeom {
 					}
 
 					if (hasParent) { ret->SetFloor(parent_object); }
+					else { ret->SetFloor(NULL); } // Set it so null in order to know that we didn't found any IfcBuildingStorey type parent
 				}
 			}