now spaces created with spatial tool have relative zero elevation origin point

src/blenderbim/blenderbim/core/spatial.py

@@ -214,7 +214,7 @@ def generate_spaces_from_walls(ifc, spatial, collector):
 
         obj = spatial.get_named_obj_from_bmesh(name, bmesh=bm)
 
-        spatial.set_obj_origin_to_bboxcenter(obj)
+        spatial.set_obj_origin_to_bboxcenter_and_zero_elevation(obj)
         spatial.traslate_obj_to_z_location(obj, z)
 
         spatial.link_obj_to_active_collection(obj)

src/blenderbim/blenderbim/core/tool.py

@@ -872,6 +872,7 @@ class Spatial:
     def get_transformed_mesh_from_local_to_global(cls, mesh): pass
     def edit_active_space_obj_from_mesh(cls, mesh): pass
     def set_obj_origin_to_bboxcenter(cls, obj): pass
+    def set_obj_origin_to_bboxcenter_and_zero_elevation(cls, obj): pass
     def set_obj_origin_to_cursor_position(cls, obj): pass
     def get_selected_objects(cls): pass
     def get_active_obj(cls): pass

src/blenderbim/blenderbim/tool/spatial.py

@@ -582,6 +582,24 @@ class Spatial(blenderbim.core.tool.Spatial):
             vert.co = inverted @ aux_vector
         obj.location = newLoc
 
+    @classmethod
+    def set_obj_origin_to_bboxcenter_and_zero_elevation(cls, obj):
+        mat = obj.matrix_world
+        inverted = mat.inverted()
+        local_bbox_center = 0.125 * sum((Vector(b) for b in obj.bound_box), Vector())
+        global_bbox_center = mat @ local_bbox_center
+        global_obj_origin = global_bbox_center
+        global_obj_origin.z = 0
+
+        oldLoc = obj.location
+        newLoc = global_obj_origin
+        diff = newLoc - oldLoc
+        for vert in obj.data.vertices:
+            aux_vector = mat @ vert.co
+            aux_vector = aux_vector - diff
+            vert.co = inverted @ aux_vector
+        obj.location = newLoc
+
     @classmethod
     def set_obj_origin_to_cursor_position(cls, obj):
         mat = obj.matrix_world