diff --git a/applications/landlord_description_overrides/handler.py b/applications/landlord_description_overrides/handler.py
index 4020bc512..a43413b4f 100644
--- a/applications/landlord_description_overrides/handler.py
+++ b/applications/landlord_description_overrides/handler.py
@@ -14,6 +14,12 @@ from domain.epc.property_overrides.main_fuel_type import MainFuelType
 from domain.epc.property_overrides.main_heating_system_type import MainHeatingSystemType
 from domain.epc.property_overrides.property_type import PropertyType
 from domain.epc.property_overrides.roof_type import RoofType
+from domain.epc.property_overrides.roof_party_ceiling_guard import (
+    roof_party_ceiling_guard,
+)
+from domain.data_transformation.guarded_column_classifier import (
+    GuardedColumnClassifier,
+)
 from domain.epc.property_overrides.water_heating_type import WaterHeatingType
 from domain.epc.property_overrides.wall_type import WallType
 from domain.epc.property_overrides.wall_type_construction_dates import (
@@ -115,8 +121,13 @@ def _build_columns(
         "roof_type": lambda src: ClassifiableColumn(
             name="roof_type",
             source_column=src,
-            classifier=ChatGptColumnClassifier(
-                chat_gpt, RoofType, RoofType.UNKNOWN
+            # A party ceiling ("another/same dwelling or premises above") has ~0
+            # heat loss and must never be classified as an external roof; the
+            # deterministic guard resolves those markers and the LLM handles the
+            # rest (#1376).
+            classifier=GuardedColumnClassifier(
+                guard=roof_party_ceiling_guard,
+                fallback=ChatGptColumnClassifier(chat_gpt, RoofType, RoofType.UNKNOWN),
             ),
             repo=LandlordOverridesRepository[RoofType](
                 session, LandlordRoofTypeOverrideRow