diff --git a/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000480.py b/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000480.py
index bdfe5d91..4e14dcc2 100644
--- a/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000480.py
+++ b/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000480.py
@@ -24,6 +24,7 @@ from datatypes.epc.domain.epc_property_data import (
     SapBuildingPart,
     SapFloorDimension,
     SapRoomInRoof,
+    SapRoomInRoofSurface,
     SapVentilation,
     SapWindow,
 )
@@ -66,6 +67,36 @@ def build_epc() -> EpcPropertyData:
         ],
         sap_room_in_roof=SapRoomInRoof(
             floor_area=19.83, construction_age_band="B",
+            # U985 §3 lines 198-202 + 211-212: 5 uninsulated surfaces
+            # (Table 17 row "none" → U=2.30) lodged on Main, plus 2
+            # gable walls routed to party at U=0.25 per Table 4. All
+            # RR surfaces sit on Main — the RR (19.83 m²) is larger
+            # than the Main storey footprint (15.28 m²) so Main has
+            # no External roof line (the entire Main roof is the RR).
+            detailed_surfaces=[
+                SapRoomInRoofSurface(
+                    kind="flat_ceiling", area_m2=2.31,
+                    insulation_thickness_mm=0,
+                ),
+                SapRoomInRoofSurface(
+                    kind="stud_wall", area_m2=4.24,
+                    insulation_thickness_mm=0,
+                ),
+                SapRoomInRoofSurface(
+                    kind="stud_wall", area_m2=4.24,
+                    insulation_thickness_mm=0,
+                ),
+                SapRoomInRoofSurface(
+                    kind="slope", area_m2=10.78,
+                    insulation_thickness_mm=0,
+                ),
+                SapRoomInRoofSurface(
+                    kind="slope", area_m2=10.78,
+                    insulation_thickness_mm=0,
+                ),
+                SapRoomInRoofSurface(kind="gable_wall", area_m2=11.33),
+                SapRoomInRoofSurface(kind="gable_wall", area_m2=8.47),
+            ],
         ),
         wall_thickness_mm=380,
     )
@@ -82,6 +113,12 @@ def build_epc() -> EpcPropertyData:
                 total_floor_area_m2=17.01,
                 party_wall_length_m=7.84, heat_loss_perimeter_m=4.34,
                 floor=0,
+                # 000480 line 207: "Exposed floor Ext1 17.01 × U=1.20"
+                # — the Ext1 ground floor sits over an unheated space
+                # (passageway / over-garage), not soil. Routes via
+                # Table 20 (`u_exposed_floor`) to U=1.20 instead of
+                # the BS EN ISO 13370 ground-contact cascade.
+                is_exposed_floor=True,
             ),
             SapFloorDimension(
                 room_height_m=3.09,  # 2.84 internal + 0.25 floor structure
@@ -92,6 +129,9 @@ def build_epc() -> EpcPropertyData:
         ],
         # NB: no alternative wall on this cert (vs 000487 which had a
         # 1.43 m² timber-frame alt wall on the extension).
+        # 000480 line 207: External roof Ext1 17.01 × U=0.14 → Table 16
+        # joist insulation 300 mm (or ≈ 270 mm row at 0.16). Pin 300 mm.
+        roof_insulation_thickness=300,
         wall_thickness_mm=380,
     )
     return make_minimal_sap10_epc(