diff --git a/domain/epc/property_overrides/roof_sloping_ceiling_guard.py b/domain/epc/property_overrides/roof_sloping_ceiling_guard.py
index 22ade4d28..e9de671cf 100644
--- a/domain/epc/property_overrides/roof_sloping_ceiling_guard.py
+++ b/domain/epc/property_overrides/roof_sloping_ceiling_guard.py
@@ -1,9 +1,29 @@
 from __future__ import annotations
 
+import re
 from typing import Optional
 
 from domain.epc.property_overrides.roof_type import RoofType
 
+# The gov-API sloping-ceiling roof token (before any ``: <insulation>`` suffix),
+# normalised to lower alphanumerics. A slope-following ceiling (roof_construction
+# 8) has no loft void, so it must resolve to the `Pitched, sloping ceiling, …`
+# family, never the loft ladder (ADR-0066).
+_SLOPING_CEILING_TOKEN = "pitchedwithslopingceiling"
+
+
+def _normalise_roof_token(description: str) -> str:
+    token = description.split(":", 1)[0]
+    return re.sub(r"[^a-z0-9]", "", token.lower())
+
 
 def roof_sloping_ceiling_guard(description: str) -> Optional[RoofType]:
-    raise NotImplementedError
+    """Deterministically resolve a `PitchedWithSlopingCeiling` roof description to
+    its `Pitched, sloping ceiling, …` RoofType member (ADR-0066).
+
+    Returns None for anything that is not a sloping-ceiling marker, so the
+    party-ceiling guard and the LLM classifier still handle the rest.
+    """
+    if _normalise_roof_token(description) != _SLOPING_CEILING_TOKEN:
+        return None
+    return RoofType.PITCHED_SLOPING_CEILING_AS_BUILT