diff --git a/src/blenderbim/blenderbim/bim/module/material/operator.py b/src/blenderbim/blenderbim/bim/module/material/operator.py
index 1399562c0a..02e1e30c73 100644
--- a/src/blenderbim/blenderbim/bim/module/material/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/material/operator.py
@@ -169,7 +169,9 @@ class UnassignMaterial(bpy.types.Operator, tool.Ifc.Operator):
         for obj in objects:
             element = tool.Ifc.get_entity(obj)
             if element:
-                ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=element)
+                material = ifcopenshell.util.element.get_material(element, should_inherit=False)
+                if "Usage" not in material.is_a():
+                    ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=element)
 
 
 class AddConstituent(bpy.types.Operator, tool.Ifc.Operator):
diff --git a/src/blenderbim/blenderbim/bim/module/model/profile.py b/src/blenderbim/blenderbim/bim/module/model/profile.py
index 0944ba858c..75a8579f6f 100644
--- a/src/blenderbim/blenderbim/bim/module/model/profile.py
+++ b/src/blenderbim/blenderbim/bim/module/model/profile.py
@@ -418,7 +418,9 @@ class DumbProfileJoiner:
         self.body = copy.deepcopy(body)
         material = ifcopenshell.util.element.get_material(element, should_skip_usage=False)
         usage = None
-        if not material or (not material.is_a("IfcMaterialProfileSet") and not material.is_a("IfcMaterialProfileSetUsage")):
+        if not material:
+            return
+        if "ProfileSet" not in material.is_a():
             return
         if material.is_a("IfcMaterialProfileSetUsage"):
             usage = material
diff --git a/src/blenderbim/test/bim/feature/material.feature b/src/blenderbim/test/bim/feature/material.feature
index db0bf23019..67ef617b4f 100644
--- a/src/blenderbim/test/bim/feature/material.feature
+++ b/src/blenderbim/test/bim/feature/material.feature
@@ -141,6 +141,7 @@ Scenario: Assign material - material layer set
     When I set "active_object.BIMObjectMaterialProperties.material_type" to "IfcMaterialLayerSet"
     And I press "bim.assign_material"
     Then the object "IfcWallType/Empty" does not have the material "Default"
+    And the object "IfcWallType/Empty" has a "0.1" thick layered material containing the material "Default"
 
 Scenario: Unassign material - material layer set
     Given an empty IFC project
@@ -155,6 +156,27 @@ Scenario: Unassign material - material layer set
     When I press "bim.unassign_material"
     Then nothing happens
 
+Scenario: Unassign material - material layer set usages will not be removed
+    Given an empty IFC project
+    And I add a cube
+    And the object "Cube" is selected
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
+    And I press "bim.assign_class"
+    And I add an empty
+    And the object "Empty" is selected
+    And I set "scene.BIMRootProperties.ifc_product" to "IfcElementType"
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWallType"
+    And I press "bim.assign_class"
+    And I press "bim.add_material(obj='')"
+    And I set "active_object.BIMObjectMaterialProperties.material_type" to "IfcMaterialLayerSet"
+    And I press "bim.assign_material"
+    And the object "IfcWall/Cube" is selected
+    When the variable "type" is "{ifc}.by_type('IfcWallType')[0].id()"
+    And I press "bim.assign_type(relating_type={type}, related_object='IfcWall/Cube')"
+    Then the object "IfcWall/Cube" has a "0.1" thick layered material containing the material "Default"
+    When I press "bim.unassign_material"
+    Then the object "IfcWall/Cube" has a "0.1" thick layered material containing the material "Default"
+
 Scenario: Enable editing assigned material - material layer set
     Given an empty IFC project
     And I add a cube
diff --git a/src/blenderbim/test/bim/feature/type.feature b/src/blenderbim/test/bim/feature/type.feature
index b274ab2bf4..3636e75927 100644
--- a/src/blenderbim/test/bim/feature/type.feature
+++ b/src/blenderbim/test/bim/feature/type.feature
@@ -1,6 +1,25 @@
 @type
 Feature: Type
 
+Scenario: Enable editing type
+    Given an empty IFC project
+    And I add a cube
+    And the object "Cube" is selected
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
+    And I press "bim.assign_class"
+    When I press "bim.enable_editing_type"
+    Then nothing happens
+
+Scenario: Disable editing type
+    Given an empty IFC project
+    And I add a cube
+    And the object "Cube" is selected
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
+    And I press "bim.assign_class"
+    And I press "bim.enable_editing_type"
+    When I press "bim.disable_editing_type"
+    Then nothing happens
+
 Scenario: Assign type - assign to an empty type
     Given an empty IFC project
     And I add a cube
@@ -31,7 +50,7 @@ Scenario: Assign type - assign to a type with representation maps
     And I press "bim.assign_type(relating_type={type}, related_object='IfcWall/Cube')"
     Then the object "IfcWall/Cube" has a "MappedRepresentation" representation of "Model/Body/MODEL_VIEW"
 
-Scenario: Assign type - assign to a type with a material layer set
+Scenario: Assign type - assign to a type with a material layer set, which automatically recreates the shape
     Given an empty IFC project
     And I add a cube
     And the object "Cube" is selected
@@ -45,17 +64,50 @@ Scenario: Assign type - assign to a type with a material layer set
     And I press "bim.add_material(obj='')"
     And I set "active_object.BIMObjectMaterialProperties.material_type" to "IfcMaterialLayerSet"
     And I press "bim.assign_material"
-    And I press "bim.enable_editing_assigned_material"
-    And the variable "layer_set" is "{ifc}.by_type("IfcMaterialLayerSet")[0].id()"
-    And I press "bim.add_layer(layer_set={layer_set})"
-    And the variable "layer" is "{ifc}.by_type("IfcMaterialLayer")[0].id()"
-    And I press "bim.enable_editing_material_set_item(material_set_item={layer})"
-    And I set "active_object.BIMObjectMaterialProperties.material_set_item_attributes[0].float_value" to "0.1"
-    And I press "bim.edit_material_set_item(material_set_item={layer})"
-    And I press "bim.edit_assigned_material(material_set={layer_set})"
     When the variable "type" is "{ifc}.by_type('IfcWallType')[0].id()"
     And I press "bim.assign_type(relating_type={type}, related_object='IfcWall/Cube')"
     Then the object "IfcWall/Cube" has a "SweptSolid" representation of "Model/Body/MODEL_VIEW"
+    And the object "IfcWall/Cube" has the material "Default"
+    And the object "IfcWall/Cube" has a "0.1" thick layered material containing the material "Default"
+    And the object "IfcWall/Cube" dimensions are "2,.1,3"
+
+Scenario: Assign type - assign to a dfferent type with a material layer set
+    Given an empty IFC project
+    And I add a cube
+    And the object "Cube" is selected
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
+    And I press "bim.assign_class"
+    And I add an empty
+    And the object "Empty" is selected
+    And I set "scene.BIMRootProperties.ifc_product" to "IfcElementType"
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWallType"
+    And I press "bim.assign_class"
+    And the variable "type" is "{ifc}.by_type('IfcWallType')[-1].id()"
+    And I press "bim.add_material(obj='')"
+    And I set "active_object.BIMObjectMaterialProperties.material_type" to "IfcMaterialLayerSet"
+    And I press "bim.assign_material"
+    And I add an empty
+    And the object "Empty" is selected
+    And I set "scene.BIMRootProperties.ifc_product" to "IfcElementType"
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWallType"
+    And I press "bim.assign_class"
+    And I set "active_object.BIMObjectMaterialProperties.material_type" to "IfcMaterialLayerSet"
+    And I press "bim.assign_material"
+    And the variable "type2" is "[w for w in {ifc}.by_type('IfcWallType') if w.id() != {type}][0].id()"
+    And the variable "layer_set" is "ifcopenshell.util.element.get_material({ifc}.by_id({type2})).id()"
+    And the variable "layer" is "{ifc}.by_id({layer_set}).MaterialLayers[0].id()"
+    And I press "bim.enable_editing_material_set_item(material_set_item={layer})"
+    And I set "active_object.BIMObjectMaterialProperties.material_set_item_attributes[0].float_value" to "0.2"
+    And I press "bim.edit_material_set_item(material_set_item={layer})"
+    And I press "bim.edit_assigned_material(material_set={layer_set})"
+    When I press "bim.assign_type(relating_type={type}, related_object='IfcWall/Cube')"
+    Then the object "IfcWall/Cube" has a "SweptSolid" representation of "Model/Body/MODEL_VIEW"
+    And the object "IfcWall/Cube" has the material "Default"
+    And the object "IfcWall/Cube" has a "0.1" thick layered material containing the material "Default"
+    And the object "IfcWall/Cube" dimensions are "2,.1,3"
+    When I press "bim.assign_type(relating_type={type2}, related_object='IfcWall/Cube')"
+    Then the object "IfcWall/Cube" has a "0.2" thick layered material containing the material "Default"
+    And the object "IfcWall/Cube" dimensions are "2,.2,3"
 
 Scenario: Assign type - assign to a type with a material profile set
     Given an empty IFC project
diff --git a/src/blenderbim/test/bim/test_feature.py b/src/blenderbim/test/bim/test_feature.py
index 1aa4c06bc4..b75c7e18d1 100644
--- a/src/blenderbim/test/bim/test_feature.py
+++ b/src/blenderbim/test/bim/test_feature.py
@@ -48,6 +48,10 @@ def replace_variables(value):
     return value
 
 
+def is_x(number, x):
+    return abs(number - x) < 1e-6
+
+
 @given("an untestable scenario")
 def an_untestable_scenario():
     pass
@@ -498,6 +502,27 @@ def the_object_name_has_the_material_material(name, material):
     assert material in [ms.material.name for ms in the_object_name_exists(name).material_slots]
 
 
+@then(
+    parsers.parse('the object "{name}" has a "{thickness}" thick layered material containing the material "{material}"')
+)
+def the_object_name_has_the_thickness_thick_layered_material_containing_the_material_material(
+    name, thickness, material
+):
+    material_name = material
+    element = tool.Ifc.get_entity(the_object_name_exists(name))
+    material = ifcopenshell.util.element.get_material(element)
+    assert material and "LayerSet" in material.is_a()
+    if material.is_a("IfcMaterialLayerSetUsage"):
+        material = material.ForLayerSet
+    total_thickness = 0
+    material_names = []
+    for layer in material.MaterialLayers or []:
+        total_thickness += layer.LayerThickness
+        material_names.append(layer.Material.Name)
+    assert is_x(total_thickness, float(thickness))
+    assert material_name in material_names
+
+
 @then(parsers.parse('the object "{name}" does not have the material "{material}"'))
 def the_object_name_does_not_have_the_material_material(name, material):
     assert material not in [ms.material.name for ms in the_object_name_exists(name).material_slots]
@@ -548,7 +573,10 @@ def the_object_name_has_no_scale(name):
 
 @then(parsers.parse('the object "{name}" dimensions are "{dimensions}"'))
 def the_object_name_dimensions_are_dimensions(name, dimensions):
-    assert list(the_object_name_exists(name).dimensions) == [float(co) for co in dimensions.split(",")]
+    actual_dimensions = list(the_object_name_exists(name).dimensions)
+    expected_dimensions = [float(co) for co in dimensions.split(",")]
+    for i, number in enumerate(actual_dimensions):
+        assert is_x(number, expected_dimensions[i])
 
 
 @then(parsers.parse('the object "{name}" bottom left corner is at "{location}"'))
diff --git a/src/ifcopenshell-python/ifcopenshell/api/material/unassign_material.py b/src/ifcopenshell-python/ifcopenshell/api/material/unassign_material.py
index e4517f500b..b79318e984 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/material/unassign_material.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/material/unassign_material.py
@@ -75,11 +75,8 @@ class Usecase:
         for rel in self.settings["product"].HasAssociations:
             if rel.is_a("IfcRelAssociatesMaterial"):
                 if rel.RelatingMaterial.is_a() in ["IfcMaterialLayerSetUsage", "IfcMaterialProfileSetUsage"]:
-                    # Usages cannot be unassigned, as all occurrences of a type
-                    # which has a parametric material must use the parametric
-                    # material. Instead, unassign the parametric material from
-                    # the type.
-                    continue
+                    # Warning: this may leave the model in a non-compliant state.
+                    self.file.remove(rel.RelatingMaterial)
                 if len(rel.RelatedObjects) == 1:
                     self.file.remove(rel)
                     continue