diff --git a/domain/epc/property_overlays/roof_type_overlay.py b/domain/epc/property_overlays/roof_type_overlay.py
index a2ba1811b..bf47c67cd 100644
--- a/domain/epc/property_overlays/roof_type_overlay.py
+++ b/domain/epc/property_overlays/roof_type_overlay.py
@@ -50,6 +50,12 @@ def _overlay_for(roof_type_value: str) -> Optional[BuildingPartOverlay]:
     match = _LOFT_MM.search(roof_type_value)
     if match is not None:
         return BuildingPartOverlay(roof_insulation_thickness=int(match.group(1)))
+    if roof_type_value.startswith("Pitched, sloping ceiling"):
+        # ADR-0066: a slope-following ceiling (gov-API roof_construction 8) has no
+        # loft void. Assert the sloping-ceiling shape so the calculator's
+        # `is_pitched_sloping_ceiling` drives the Table 18 col (3) age-band default
+        # ("as built"), never the loft ladder. Leave thickness None here.
+        return BuildingPartOverlay(roof_construction_type="Pitched, sloping ceiling")
     if roof_type_value.startswith("Flat,"):
         flat_depth = _FLAT_MM.search(roof_type_value)
         if flat_depth is not None: