diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index 0f1b8bad..bc8c7957 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -2549,7 +2549,9 @@ class EpcPropertyDataMapper:
                 SapFlatDetails(
                     level=schema.sap_flat_details.level,
                     top_storey=schema.sap_flat_details.top_storey,
-                    flat_location=schema.sap_flat_details.flat_location,
+                    flat_location=_flat_location_int(
+                        schema.sap_flat_details.flat_location
+                    ),
                     heat_loss_corridor=schema.sap_flat_details.heat_loss_corridor,
                     storey_count=schema.sap_flat_details.storey_count,
                     unheated_corridor_length_m=(
@@ -3111,6 +3113,17 @@ def _clear_basement_flag_when_system_built(
     return replace(epc, sap_building_parts=new_parts)
 
 
+def _flat_location_int(value: Any) -> int:
+    """`sap_flat_details.flat_location` is the flat's floor number, lodged by the
+    gov API as a plain int on most certs but as a banded string `"20+"` (floor 20
+    or above) on high floors. The `epc_flat_details.flat_location` column is a
+    NOT-NULL integer, so the raw band crashed the modelling_e2e insert. Coerce the
+    band to its floor (`"20+"` → 20); Elmhurst caps the floor number at 30."""
+    if isinstance(value, int):
+        return value
+    return int(str(value).strip().rstrip("+"))
+
+
 def _measurement_value(field: Any) -> float:
     """SAP measurements arrive as a `Measurement` (with `.value`), a raw dict
     {'value': N, 'quantity': '...'} when `from_dict` didn't coerce, or a plain