diff --git a/city_model_structure/attributes/surface.py b/city_model_structure/attributes/surface.py
index 168b8eb8..65be7837 100644
--- a/city_model_structure/attributes/surface.py
+++ b/city_model_structure/attributes/surface.py
@@ -50,11 +50,13 @@ class Surface:
     :return str
     """
     if self._id is None:
-      self._id = self.name.replace('-', '').replace('a', '').replace('b', '').replace('c', '').replace('d', '')
-      self._id = self._id.replace('e', '').replace('f', '')
-      print(self._id)
+      raise ValueError('Undefined surface id')
     return self._id
 
+  @id.setter
+  def id(self, value):
+    self._id = value
+
   @property
   def swr(self):
     """
diff --git a/city_model_structure/building.py b/city_model_structure/building.py
index 71d2282f..cc6916e8 100644
--- a/city_model_structure/building.py
+++ b/city_model_structure/building.py
@@ -59,10 +59,11 @@ class Building(CityObject):
     self._thermal_zones.append(ThermalZone(zone_surfaces))
     for t_zones in self._thermal_zones:
       t_zones.bounded = [ThermalBoundary(s, [t_zones]) for s in t_zones.surfaces]
-    for surface in self.surfaces:
+    for surface_id, surface in enumerate(self.surfaces):
       self._min_x = min(self._min_x, surface.bounds_lower_corner[0])
       self._min_y = min(self._min_y, surface.bounds_lower_corner[1])
       self._min_z = min(self._min_z, surface.bounds_lower_corner[2])
+      surface.id = surface_id
       if surface.type == 'Ground':
         self._grounds.append(surface)
       elif surface.type == 'Wall':