diff --git a/datatypes/epc/domain/tests/test_from_site_notes.py b/datatypes/epc/domain/tests/test_from_site_notes.py
index da5b68768..8e31f0ae6 100644
--- a/datatypes/epc/domain/tests/test_from_site_notes.py
+++ b/datatypes/epc/domain/tests/test_from_site_notes.py
@@ -615,6 +615,29 @@ class TestFloorExposureMapping:
         assert upper.is_exposed_floor is False
         assert upper.is_above_partially_heated_space is False
 
+    def test_same_dwelling_below_lodges_party_floor_with_no_heat_loss(self) -> None:
+        # "Same dwelling below" is an internal floor between heated storeys of
+        # one dwelling — RdSAP 10 §3 gives it NO floor heat loss. Mirrors the
+        # gov-API code-8 precedent: normalize to the "(another dwelling
+        # below)" suppression string `heat_transmission.py` substring-matches
+        # to zero the part's floor loss, and keep both Table 20/§5.14
+        # exposure flags off (it is neither exposed nor above a partially
+        # heated space).
+        # Arrange
+        data = load("pashub_rdsap_site_notes_example1.json")
+        data["building_construction"]["floor"]["floor_type"] = "Same dwelling below"
+        survey = from_dict(PasHubRdSapSiteNotes, data)
+
+        # Act
+        result = EpcPropertyDataMapper.from_site_notes(survey)
+
+        # Assert — the party-floor suppression string and no exposure flags.
+        part = result.sap_building_parts[0]
+        assert part.floor_type == "(another dwelling below)"
+        ground = self._ground(part)
+        assert ground.is_exposed_floor is False
+        assert ground.is_above_partially_heated_space is False
+
     def test_ground_floor_type_leaves_both_flags_off(self) -> None:
         # Arrange — the fixture as lodged ("Ground Floor").
         survey = from_dict(