diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index f9b004cfc..aee3d3b40 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -170,6 +170,14 @@ _MAIN_HEATING_CODES: dict[str, int] = {
     # Modern standalone oil room heater — SAP Table 4a 623 ("Oil room heater,
     # 2000 or later", no boiler). Natural fuel heating oil (ADR-0041).
     "Oil room heater, 2000 or later": 623,
+    # Gas room heaters — each catalogue variant to its own SAP Table 4a code
+    # (wide efficiency spread, so no single representative). Natural fuel mains
+    # gas; an LPG dwelling is refined by a `main_fuel` override (ADR-0041).
+    "Gas room heater, condensing fire": 611,
+    "Gas room heater, decorative fuel-effect": 612,
+    "Gas room heater, flush live-effect": 605,
+    "Gas room heater, open flue 1980 or later": 603,
+    "Gas room heater, open flue pre-1980": 601,
 }
 
 
diff --git a/domain/epc/property_overrides/main_heating_system_type.py b/domain/epc/property_overrides/main_heating_system_type.py
index c15afd602..eb4658b84 100644
--- a/domain/epc/property_overrides/main_heating_system_type.py
+++ b/domain/epc/property_overrides/main_heating_system_type.py
@@ -29,4 +29,9 @@ class MainHeatingSystemType(Enum):
     AIR_SOURCE_HEAT_PUMP = "Air source heat pump"
     COMMUNITY_BOILERS = "Community heating, boilers"
     OIL_ROOM_HEATER_POST_2000 = "Oil room heater, 2000 or later"
+    GAS_FIRE_CONDENSING = "Gas room heater, condensing fire"
+    GAS_FIRE_DECORATIVE = "Gas room heater, decorative fuel-effect"
+    GAS_FIRE_FLUSH_LIVE_EFFECT = "Gas room heater, flush live-effect"
+    GAS_FIRE_OPEN_FLUE_POST_1980 = "Gas room heater, open flue 1980 or later"
+    GAS_FIRE_OPEN_FLUE_PRE_1980 = "Gas room heater, open flue pre-1980"
     UNKNOWN = "Unknown"