diff --git a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
index 164063c6..f8a79eef 100644
--- a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
+++ b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
@@ -313,6 +313,33 @@ def test_summary_001479_secondary_heating_routes_mains_gas_fuel() -> None:
     assert epc.sap_heating.secondary_fuel_type == 26
 
 
+def test_summary_2102_secondary_heating_routes_house_coal_for_open_fire() -> None:
+    # Arrange — cohort-2 cert 2102-3018-0205-7886-5204 §14.1 lodges
+    # "Secondary Heating Code: SAP code 631" — "Open fire in grate"
+    # per SAP 10.2 Table 4a Category 10 (Room heaters), solid fuel
+    # column. Without the per-code routing the cascade defaults to
+    # standard electricity at 13.19 p/kWh and over-charges secondary
+    # heating by ~£340/yr, pushing SAP -15.81 below the worksheet's
+    # 63.87. Worksheet line (242) "Space heating - secondary 3585.24
+    # × 3.6700 = 131.58" confirms house-coal pricing (Table 32 fuel
+    # code 11 = 3.67 p/kWh).
+    cert_dir = Path(
+        "sap worksheets/additional with api 2/2102-3018-0205-7886-5204"
+    )
+    summary_pdf = next(cert_dir.glob("Summary_*.pdf"))
+    pages = _summary_pdf_to_textract_style_pages(summary_pdf)
+    site_notes = ElmhurstSiteNotesExtractor(pages).extract()
+
+    # Act
+    epc = EpcPropertyDataMapper.from_elmhurst_site_notes(site_notes)
+
+    # Assert
+    assert epc.sap_heating.secondary_heating_type == 631
+    # 11 = "Coal" in `_ELMHURST_MAIN_FUEL_TO_SAP10` → Table 32 lookup
+    # returns 3.67 p/kWh (house coal).
+    assert epc.sap_heating.secondary_fuel_type == 11
+
+
 def test_summary_9501_flat_has_no_built_form_in_summary_pdf() -> None:
     # Arrange — cert 9501 (Summary_000784.pdf) is a flat. The Elmhurst
     # Summary's §1.0 "Property type" section lodges the built-form
diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index ce8162ed..194d6d7d 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -3350,14 +3350,31 @@ def _elmhurst_secondary_fuel_from_sap_code(
     fitting live effect gas fire") but not the fuel int separately; the
     cascade's `_secondary_fuel_cost_gbp_per_kwh` defaults to standard
     electricity when `secondary_fuel_type` is None — correct for the
-    portable-electric default but wrong for cert 001479's mains-gas fire.
-    Returns 26 (mains gas) for SAP codes in the 600-630 range; None for
-    other codes (cascade default fires, matching cohort 000490 SAP code
-    691 electric panel)."""
+    portable-electric default but wrong for fuel-fired room heaters.
+
+    SAP 10.2 Table 4a Category 10 ("Room heaters") code blocks:
+      601-613: Gas (mains gas / LPG / biogas) — column A is mains gas;
+               column B for LPG. Cohort default is mains gas
+               (`_ELMHURST_MAIN_FUEL_TO_SAP10["Mains gas"] = 26`).
+      621-625: Liquid fuel room heaters (oil / bioethanol). Cohort
+               not yet exercised; deferred until a fixture surfaces.
+      631-634: Solid fuel room heaters (open fire, closed room
+               heater with/without boiler). House coal is the modal
+               default per Table 12 secondary rate (3.67 p/kWh).
+      691-699: Electric room heaters. Cascade default (None) routes
+               to standard electricity (13.19 p/kWh).
+
+    Cohort cert 2102-3018-0205-7886-5204 surfaces the 631 ("Open fire
+    in grate") path — pre-slice the cascade defaulted to electricity
+    at 13.19 p/kWh, over-charging secondary by ~£340/yr and pushing
+    SAP -15.81 below the worksheet's 63.87.
+    """
     if sap_code is None:
         return None
-    if 601 <= sap_code <= 630:
+    if 601 <= sap_code <= 613:
         return 26  # Mains gas, matching `_ELMHURST_MAIN_FUEL_TO_SAP10`
+    if 631 <= sap_code <= 634:
+        return 11  # House coal (Coal in `_ELMHURST_MAIN_FUEL_TO_SAP10`)
     return None