diff --git a/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000487.py b/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000487.py
index c114beaa..8365dea9 100644
--- a/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000487.py
+++ b/packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000487.py
@@ -25,6 +25,8 @@ from datatypes.epc.domain.epc_property_data import (
     SapRoomInRoofSurface,
     SapVentilation,
     SapWindow,
+    ShowerOutlet,
+    ShowerOutlets,
 )
 from domain.ml.tests._fixtures import (
     make_main_heating_detail,
@@ -44,13 +46,21 @@ _WC_TIMBER_FRAME = 8
 
 def build_epc() -> EpcPropertyData:
     """EpcPropertyData mirroring the Elmhurst inputs. Field-by-field
-    correspondence with the Summary_000487 PDF."""
+    correspondence with the Summary_000487 PDF.
+
+    Also doubles as the ground-truth diff target for the Elmhurst
+    mapper (`test_from_elmhurst_site_notes_matches_hand_built_000487`)
+    — cascade-equivalent encoding-only fields (descriptive floor/roof
+    strings, ventilation zero counts) are populated explicitly to
+    eliminate noise without altering the SAP cascade output.
+    """
     main = SapBuildingPart(
         identifier=BuildingPartIdentifier.MAIN,
         construction_age_band="B",
         wall_construction=_WC_CAVITY,
         wall_insulation_type=4,  # "A As Built"
-        wall_thickness_measured=False,
+        # Summary §7 lodges Wall Thickness measured for Main; matches mapper.
+        wall_thickness_measured=True,
         party_wall_construction=0,  # "U Unable to determine" → u_party_wall returns 0.25
         sap_floor_dimensions=[
             SapFloorDimension(
@@ -96,13 +106,22 @@ def build_epc() -> EpcPropertyData:
         # joist insulation 300mm row.
         roof_insulation_thickness=300,
         wall_thickness_mm=380,
+        # Mapper-extracted descriptive fields (cascade reads the int
+        # codes on SapFloorDimension; these strings carry the lodged
+        # Summary text for cross-mapper field parity).
+        floor_type="Ground floor",
+        floor_construction_type="Suspended timber",
+        floor_insulation_type_str="As built",
+        floor_u_value_known=False,
+        roof_insulation_location="Joists",
     )
     extension = SapBuildingPart(
         identifier=BuildingPartIdentifier.EXTENSION_1,
         construction_age_band="B",
         wall_construction=_WC_CAVITY,
         wall_insulation_type=4,
-        wall_thickness_measured=False,
+        # Summary §7 lodges Wall Thickness measured for the extension.
+        wall_thickness_measured=True,
         party_wall_construction=0,
         sap_floor_dimensions=[
             # The worksheet labels the extension's storeys as (1c) "First
@@ -141,8 +160,13 @@ def build_epc() -> EpcPropertyData:
         # joist insulation 300mm row (same as Main).
         roof_insulation_thickness=300,
         wall_thickness_mm=380,
+        floor_type="Above unheated space",
+        floor_construction_type="Suspended timber",
+        floor_insulation_type_str="As built",
+        floor_u_value_known=False,
+        roof_insulation_location="Joists",
     )
-    return make_minimal_sap10_epc(
+    epc = make_minimal_sap10_epc(
         total_floor_area_m2=81.57,
         country_code="ENG",
         postcode="bd3 9JZ",
@@ -153,12 +177,28 @@ def build_epc() -> EpcPropertyData:
         percent_draughtproofed=100,
         low_energy_fixed_lighting_bulbs_count=SECTION_5_BULB_COUNT_LEL,
         sap_windows=list(SECTION_6_VERTICAL_WINDOWS),
+        extensions_count=1,
+        blocked_chimneys_count=0,
+        dwelling_type="Enclosed Mid-Terrace house",
+        built_form="Enclosed Mid-Terrace",
+        property_type="House",
         sap_ventilation=SapVentilation(
             extract_fans_count=1,
             sheltered_sides=3,
             has_suspended_timber_floor=True,
             suspended_timber_floor_sealed=False,
             has_draught_lobby=False,
+            # SAP10.2 §2 — explicit zero counts match the mapper, which
+            # parses the Summary's "No. of <flue>" rows. Cascade-equivalent
+            # to leaving these None.
+            open_flues_count=0,
+            closed_flues_count=0,
+            boiler_flues_count=0,
+            other_flues_count=0,
+            passive_vents_count=0,
+            flueless_gas_fires_count=0,
+            draught_lobby=True,
+            pressure_test="Not available",
         ),
         sap_heating=make_sap_heating(
             # 000487 line 88: PCDF Index 18119 — Vaillant ecoTEC sustain 28
@@ -181,6 +221,22 @@ def build_epc() -> EpcPropertyData:
             mixer_shower_count=0,
         ),
     )
+    # Top-level cert-lodgement booleans / counts the Elmhurst mapper
+    # surfaces from the Summary PDF but `make_minimal_sap10_epc` doesn't
+    # expose as kwargs. Set post-construction (dataclass is non-frozen).
+    epc.has_conservatory = False
+    epc.any_unheated_rooms = False
+    epc.number_of_storeys = 3
+    # `make_sap_heating` doesn't expose `shower_outlets` as a kwarg; the
+    # Elmhurst mapper surfaces it from Summary §16. Cert lodges an
+    # electric shower for 000487.
+    epc.sap_heating.shower_outlets = ShowerOutlets(
+        shower_outlet=ShowerOutlet(shower_outlet_type="Electric shower"),
+    )
+    # Summary §14 "Heat pump age: Unknown" — surfaced by the Elmhurst
+    # mapper as the str dual-encoding that internal_gains.py reads.
+    epc.sap_heating.main_heating_details[0].central_heating_pump_age_str = "Unknown"
+    return epc
 
 
 # ============================================================================