diff --git a/recommendations/recommendation_utils.py b/recommendations/recommendation_utils.py
index d5788544..00da6107 100644
--- a/recommendations/recommendation_utils.py
+++ b/recommendations/recommendation_utils.py
@@ -205,7 +205,7 @@ def get_wall_u_value(
 
         mapped_value = wall_uvalues_df[
             wall_uvalues_df["Wall_type"] == mapped_description
-            ][age_band].values[0]
+        ][age_band].values[0]
 
         if pd.isnull(mapped_value) and "Park home" in mapped_description:
             # We don't know enough in this case so we default to 0
@@ -257,7 +257,7 @@ def extract_thickness(thickness, is_roof_room, is_at_rafters, is_loft, is_flat):
         try:
             thickness = int(thickness)
             return thickness
-        except ValueError:
+        except (TypeError, ValueError):
             # If thickness is not a valid number (could be a string or None), return None
             return None
 
@@ -350,7 +350,7 @@ def get_roof_u_value(
         is_roof_room=is_roof_room,
         is_at_rafters=is_at_rafters,
         is_loft=is_loft,
-        is_flat=is_flat
+        is_flat=is_flat,
     )
 
     # Step 1: Try to get the U-value from table S9 based on the insulation thickness
@@ -395,9 +395,9 @@ def get_roof_u_value(
     # Get the U-value from table S10 based on the age band and the determined column
     if is_flat and thickness is not None:
         u_value = s10.loc[
-            (s10["Insulation_Thickness"] == thickness) |
-            s10["Age_band"].str.contains(age_band),
-            column
+            (s10["Insulation_Thickness"] == thickness)
+            | s10["Age_band"].str.contains(age_band),
+            column,
         ].values.min()
     else:
         u_value = s10.loc[s10["Age_band"].str.contains(age_band), column].values[0]
@@ -560,7 +560,7 @@ def get_floor_u_value(
         insulation_lookup = s11[
             s11["Age_band"].str.contains(age_band) & s11["Floor_construction"]
             == floor_type
-            ]
+        ]
         if insulation_lookup.empty:
             insulation_thickness = 0
         else: