diff --git a/tests/domain/modelling/test_roof_recommendation.py b/tests/domain/modelling/test_roof_recommendation.py
index 77e9c0124..6759341ed 100644
--- a/tests/domain/modelling/test_roof_recommendation.py
+++ b/tests/domain/modelling/test_roof_recommendation.py
@@ -170,9 +170,12 @@ def test_vaulted_ceiling_with_measured_thickness_yields_no_recommendation() -> N
 def test_loft_roof_with_nd_thickness_on_pre_1950_dwelling_yields_loft_insulation() -> None:
     # Arrange — the loft fallback shares the sentinel semantics (ADR-0047):
     # "ND" on an age-band-C pitched loft resolves to as-built uninsulated, so
-    # the joist measure fires just as it does for an explicit 0.
+    # the joist measure fires just as it does for an explicit 0. The lodged
+    # type is the gov-API code-4 string — sentinel resolution needs a KNOWN
+    # pitched roof (an unlodged type could be a party ceiling; see below).
     baseline: EpcPropertyData = build_epc()
     main: SapBuildingPart = _part(baseline, BuildingPartIdentifier.MAIN)
+    main.roof_construction_type = "Pitched (slates/tiles), access to loft"
     main.roof_insulation_thickness = "ND"
     main.construction_age_band = "C"
 
@@ -191,6 +194,28 @@ def test_loft_roof_with_nd_thickness_on_pre_1950_dwelling_yields_loft_insulation
     )
 
 
+def test_unlodged_roof_type_with_nd_thickness_yields_no_recommendation() -> None:
+    # Arrange — a part with NO lodged roof type reaching the loft fallback can
+    # be a party ceiling ("(another dwelling above)", gov-API codes 6/7 map the
+    # type to None and real code-7 certs lodge "ND"): zero roof heat loss, so
+    # insulating it contradicts the dwelling. Sentinel resolution therefore
+    # requires a KNOWN pitched/thatched roof; an unlodged type keeps the
+    # explicit-0-only trigger (ADR-0047).
+    baseline: EpcPropertyData = build_epc()
+    main: SapBuildingPart = _part(baseline, BuildingPartIdentifier.MAIN)
+    main.roof_construction_type = None
+    main.roof_insulation_thickness = "ND"
+    main.construction_age_band = "B"
+
+    # Act
+    recommendation: Recommendation | None = recommend_roof_insulation(
+        baseline, _StubProducts()
+    )
+
+    # Assert
+    assert recommendation is None
+
+
 def test_loft_option_carries_cost_from_roof_area_and_product() -> None:
     # Arrange
     baseline: EpcPropertyData = build_epc()  # MAIN roof area 14.85 m^2