diff --git a/backend/SearchEpc.py b/backend/SearchEpc.py
index 8dde4f8b..6fbdb3ea 100644
--- a/backend/SearchEpc.py
+++ b/backend/SearchEpc.py
@@ -472,8 +472,9 @@ class SearchEpc:
                         # missing, so we fill with 1
                         epc_data["weight"] = epc_data["weight"].fillna(1)
 
-                    epc_property_type = self._estimate_str(key="property-type", estimation_data=epc_data)
-                    estimation_property_type = epc_property_type if property_type == "" else property_type
+                    estimation_property_type = self._estimate_str(
+                        key="property-type", estimation_data=epc_data
+                    ) if property_type == "" else property_type
 
                     epc_built_form = self._estimate_str(
                         key="built-form",
@@ -482,7 +483,7 @@ class SearchEpc:
 
                     if built_form == "Semi-Detached" and epc_built_form in ["End-Terraced", "Mid-Terraced"]:
                         estimation_built_form = "End-Terraced"
-                    elif built_form == "":
+                    elif (built_form == "") or (pd.isnull(built_form)):
                         estimation_built_form = epc_built_form
                     else:
                         estimation_built_form = built_form
@@ -492,13 +493,17 @@ class SearchEpc:
                     # We also add some additional logic for Park homes, because they are far less common than other
                     # property types
 
-                    if (estimation_property_type == "Maisonette") & (
+                    is_maisonette_with_bad_built_form = (estimation_property_type == "Maisonette") & (
                         estimation_built_form in ["Detached", "Semi-Detached"]
-                    ):
-                        epc_data = epc_data[epc_data["property-type"] == estimation_property_type]
-                    elif (estimation_property_type == "Park home") & (
+                    )
+
+                    is_park_home_without_built_form = (estimation_property_type == "Park home") & (
                         sum(epc_data["built-form"] == estimation_built_form) == 0
-                    ):
+                    )
+
+                    has_missing_built_form = not estimation_built_form
+
+                    if is_maisonette_with_bad_built_form or is_park_home_without_built_form or has_missing_built_form:
                         epc_data = epc_data[epc_data["property-type"] == estimation_property_type]
                     else:
                         epc_data = epc_data[