diff --git a/scripts/reclassify_party_ceiling_roofs.py b/scripts/reclassify_party_ceiling_roofs.py
new file mode 100644
index 000000000..3727fa7ef
--- /dev/null
+++ b/scripts/reclassify_party_ceiling_roofs.py
@@ -0,0 +1,132 @@
+"""One-time re-classification of party-ceiling roof overrides mis-read as roofs.
+
+#1376: a landlord roof description that is a **party-ceiling** marker ("another /
+same dwelling or premises above") was occasionally classified by the LLM to an
+external ``Pitched, N mm loft insulation`` value when it carried a trailing depth —
+inventing roof heat loss where a party ceiling has ~0 (RdSAP 10 Table 18: "There
+is no heat loss through the roof of a building part that has the same dwelling or
+another dwelling above"). ~106 ``property_overrides`` rows (party-ceiling markers
+on any non-party-ceiling value), inconsistent with the ~13k of the same family
+already resolving to the party-ceiling member.
+
+The live classifier now applies ``roof_party_ceiling_guard`` deterministically
+(so new intakes are correct); this fixes the rows written before it. The **same
+guard** decides the correction here, so the backfill and the live path cannot
+drift.
+
+Updates the TEXT ``property_overrides.override_value`` (what the modelling reads —
+the actual fix) and the ``landlord_roof_type_overrides.value`` classifier cache.
+The party-ceiling members already exist in the roof pgEnum (13k rows store them),
+so no FE migration is needed.
+
+DRY-RUN BY DEFAULT: prints the row count it would change and writes nothing. Pass
+``--apply`` to execute inside a transaction. Idempotent — only rows whose stored
+value differs from the guard's member are touched, so a second run is a no-op.
+"""
+
+from __future__ import annotations
+
+import argparse
+from collections.abc import Iterable
+
+from sqlalchemy import Connection, text
+
+from domain.epc.property_overrides.roof_party_ceiling_guard import (
+    roof_party_ceiling_guard,
+)
+from scripts.e2e_common import build_engine, load_env
+
+
+def party_ceiling_corrections(
+    stored: Iterable[tuple[str, str]],
+) -> dict[str, str]:
+    """``(description, stored override_value)`` → the corrected value, for the
+    descriptions the party-ceiling guard resolves whose stored value is not already
+    the guard's member. Descriptions the guard leaves to the LLM (``None``) and
+    rows already on the right member are omitted — so the result is exactly the set
+    to fix, and re-running against corrected data yields an empty map (idempotent).
+    """
+    corrections: dict[str, str] = {}
+    for description, value in stored:
+        member = roof_party_ceiling_guard(description)
+        if member is not None and value != member.value:
+            corrections[description] = member.value
+    return corrections
+
+
+_DISTINCT = text(
+    """
+    SELECT DISTINCT lower(original_spreadsheet_description) AS description,
+                    override_value AS value
+    FROM property_overrides
+    WHERE override_component = 'roof_type'
+    """
+)
+_OVERRIDES_UPDATE = text(
+    """
+    UPDATE property_overrides
+       SET override_value = :new_value
+     WHERE override_component = 'roof_type'
+       AND lower(original_spreadsheet_description) = :description
+       AND override_value <> :new_value
+    """
+)
+_CACHE_UPDATE = text(
+    """
+    UPDATE landlord_roof_type_overrides
+       SET value = :new_value, updated_at = now()
+     WHERE lower(description) = :description
+       AND value::text <> :new_value
+    """
+)
+_OVERRIDES_COUNT = text(
+    """
+    SELECT count(*) FROM property_overrides
+     WHERE override_component = 'roof_type'
+       AND lower(original_spreadsheet_description) = :description
+       AND override_value <> :new_value
+    """
+)
+
+
+def reclassify(conn: Connection, *, apply: bool) -> int:
+    """NULL-free re-map: set every mis-classified party-ceiling roof override to the
+    guard's member. Returns the number of ``property_overrides`` rows found (that
+    ``--apply`` would / did correct)."""
+    stored = [(r.description, r.value) for r in conn.execute(_DISTINCT)]
+    total = 0
+    for description, new_value in party_ceiling_corrections(stored).items():
+        params = {"description": description, "new_value": new_value}
+        total += conn.execute(_OVERRIDES_COUNT, params).scalar() or 0
+        if apply:
+            conn.execute(_OVERRIDES_UPDATE, params)
+            conn.execute(_CACHE_UPDATE, params)
+    return total
+
+
+def main() -> None:
+    load_env()
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "--apply",
+        action="store_true",
+        help="execute the updates (default: dry-run, writes nothing)",
+    )
+    args = parser.parse_args()
+
+    engine = build_engine()
+    with engine.begin() as conn:
+        conn.execute(text("SET statement_timeout = 120000"))
+        total = reclassify(conn, apply=args.apply)
+
+    verb = "re-classified" if args.apply else "would re-classify"
+    print(
+        f"{verb} {total} party-ceiling roof override row(s) from an external "
+        "roof value to the party-ceiling member."
+    )
+    if not args.apply:
+        print("\nDRY-RUN — nothing written. Re-run with --apply to execute.")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tests/scripts/test_reclassify_party_ceiling_roofs.py b/tests/scripts/test_reclassify_party_ceiling_roofs.py
new file mode 100644
index 000000000..513e510d5
--- /dev/null
+++ b/tests/scripts/test_reclassify_party_ceiling_roofs.py
@@ -0,0 +1,33 @@
+"""The party-ceiling roof reclassify corrects only the mis-read rows, to the
+guard's member, and is idempotent (#1376)."""
+
+from __future__ import annotations
+
+from scripts.reclassify_party_ceiling_roofs import party_ceiling_corrections
+
+
+def test_only_misclassified_party_ceiling_rows_are_corrected() -> None:
+    # Arrange — a party ceiling mis-read as an external pitched roof (the bug),
+    # one already on the correct member, and a genuine pitched roof.
+    stored = [
+        ("another dwelling above: 100mm", "Pitched, 100 mm loft insulation"),
+        ("another dwelling above: unknown", "(another dwelling above)"),
+        ("pitched, normal loft access: 150mm", "Pitched, 150 mm loft insulation"),
+    ]
+
+    # Act
+    corrections = party_ceiling_corrections(stored)
+
+    # Assert — only the mis-read party ceiling is corrected, to its member value;
+    # the already-correct row and the genuine pitched roof are left alone.
+    assert corrections == {
+        "another dwelling above: 100mm": "(another dwelling above)"
+    }
+
+
+def test_already_corrected_data_yields_no_further_corrections() -> None:
+    # Arrange — a re-run over data the first pass already fixed.
+    stored = [("another dwelling above: 100mm", "(another dwelling above)")]
+
+    # Act / Assert — idempotent: nothing left to change.
+    assert party_ceiling_corrections(stored) == {}