diff --git a/domain/epc_prediction/prediction_comparison.py b/domain/epc_prediction/prediction_comparison.py
index 9332bca6..391b5149 100644
--- a/domain/epc_prediction/prediction_comparison.py
+++ b/domain/epc_prediction/prediction_comparison.py
@@ -85,6 +85,49 @@ def _age_band_within_one(predicted: object, actual: object) -> Optional[bool]:
     return False
 
 
+# RdSAP roof-insulation thickness buckets, thinnest → thickest. Uninsulated is
+# lodged as either 0 or "NI" (not insulated), so both map to the bottom rung;
+# "ND" (no data) is off the scale entirely. Adjacent buckets carry near-identical
+# roof U-values, so an off-by-one bucket is treated as a (SAP-neutral) ±1 hit —
+# the same measurement honesty as the construction age band (issue #1222).
+_ROOF_THICKNESS_ORDINAL: dict[object, int] = {
+    0: 0,
+    "NI": 0,
+    "12mm": 1,
+    "25mm": 2,
+    "50mm": 3,
+    "75mm": 4,
+    "100mm": 5,
+    "125mm": 6,
+    "150mm": 7,
+    "175mm": 8,
+    "200mm": 9,
+    "225mm": 10,
+    "250mm": 11,
+    "270mm": 12,
+    "300mm": 13,
+    "350mm": 14,
+    "400mm+": 15,
+}
+
+
+def _roof_insulation_within_one(
+    predicted: object, actual: object
+) -> Optional[bool]:
+    """A ±1-bucket roof-insulation hit: None when the actual is absent, True on an
+    exact or adjacent-bucket match, else False. Off the ordered scale (e.g. the
+    "ND" no-data category) only an exact match counts."""
+    if actual is None:
+        return None
+    if predicted == actual:
+        return True
+    pred_rung = _ROOF_THICKNESS_ORDINAL.get(predicted)
+    actual_rung = _ROOF_THICKNESS_ORDINAL.get(actual)
+    if pred_rung is None or actual_rung is None:
+        return False
+    return abs(pred_rung - actual_rung) <= 1
+
+
 def _main_heating_detail(epc: EpcPropertyData) -> Optional[MainHeatingDetail]:
     """The primary heating system's detail row, or None when none is lodged."""
     details = epc.sap_heating.main_heating_details
@@ -159,6 +202,10 @@ def _renewables_and_fabric_hits(
             _main(predicted).roof_insulation_thickness,
             _main(actual).roof_insulation_thickness,
         ),
+        "roof_insulation_thickness_pm1": _roof_insulation_within_one(
+            _main(predicted).roof_insulation_thickness,
+            _main(actual).roof_insulation_thickness,
+        ),
         "floor_insulation": _classify(
             _main_floor_insulation(predicted), _main_floor_insulation(actual)
         ),
diff --git a/tests/domain/epc_prediction/test_component_accuracy_gate.py b/tests/domain/epc_prediction/test_component_accuracy_gate.py
index f14942f7..71e19fd1 100644
--- a/tests/domain/epc_prediction/test_component_accuracy_gate.py
+++ b/tests/domain/epc_prediction/test_component_accuracy_gate.py
@@ -45,6 +45,7 @@ _RATE_FLOORS: dict[str, float] = {
     "cylinder_insulation_type": 0.5000,
     "secondary_heating_type": 0.0000,
     "roof_insulation_thickness": 0.4118,
+    "roof_insulation_thickness_pm1": 0.4118,
     "floor_insulation": 0.9375,
     "has_room_in_roof": 0.8333,
     "modal_glazing_type": 0.5278,
diff --git a/tests/domain/epc_prediction/test_prediction_comparison.py b/tests/domain/epc_prediction/test_prediction_comparison.py
index ab19f5ef..357530bc 100644
--- a/tests/domain/epc_prediction/test_prediction_comparison.py
+++ b/tests/domain/epc_prediction/test_prediction_comparison.py
@@ -38,9 +38,9 @@ def _epc(
     door_count: int = 2,
     has_pv: bool = False,
     solar_water_heating: bool = False,
-    main_fuel_type: Optional[int] = 20,
+    main_fuel_type: Union[int, str] = 20,
     main_heating_category: Optional[int] = 2,
-    main_heating_control: Optional[Union[int, str]] = 2100,
+    main_heating_control: Union[int, str] = 2100,
     water_heating_fuel: Optional[int] = 20,
     water_heating_code: Optional[int] = 901,
     has_hot_water_cylinder: bool = True,
@@ -125,6 +125,49 @@ def test_age_band_two_apart_misses_both() -> None:
     assert hits["construction_age_band_pm1"] is False
 
 
+def test_scores_roof_insulation_within_one_bucket() -> None:
+    # Arrange — predicted 250mm, actual 270mm (adjacent RdSAP buckets). Adjacent
+    # thicknesses carry near-identical roof U-values, so it misses the exact hit
+    # but counts as a ±1-bucket hit, like the age band (issue #1222).
+    predicted = _epc(roof_insulation_thickness="250mm")
+    actual = _epc(roof_insulation_thickness="270mm")
+
+    # Act
+    hits = compare_prediction(predicted, actual).categorical_hits
+
+    # Assert
+    assert hits["roof_insulation_thickness"] is False
+    assert hits["roof_insulation_thickness_pm1"] is True
+
+
+def test_roof_insulation_two_buckets_apart_misses_both() -> None:
+    # Arrange — predicted 100mm, actual 200mm (three buckets apart: 100/150/200):
+    # a real miss on both exact and ±1.
+    predicted = _epc(roof_insulation_thickness="100mm")
+    actual = _epc(roof_insulation_thickness="200mm")
+
+    # Act
+    hits = compare_prediction(predicted, actual).categorical_hits
+
+    # Assert
+    assert hits["roof_insulation_thickness"] is False
+    assert hits["roof_insulation_thickness_pm1"] is False
+
+
+def test_roof_insulation_off_scale_no_data_only_exact_counts() -> None:
+    # Arrange — actual is the off-scale "ND" (no-data) category; a non-equal
+    # prediction can't be an adjacent-bucket hit.
+    predicted = _epc(roof_insulation_thickness="200mm")
+    actual = _epc(roof_insulation_thickness="ND")
+
+    # Act
+    hits = compare_prediction(predicted, actual).categorical_hits
+
+    # Assert
+    assert hits["roof_insulation_thickness"] is False
+    assert hits["roof_insulation_thickness_pm1"] is False
+
+
 def test_flags_a_correct_main_wall_construction_classification() -> None:
     # Arrange — predicted and actual agree on cavity (1).
     predicted = _epc(wall_construction=1)