diff --git a/domain/epc/property_overlays/water_heating_overlay.py b/domain/epc/property_overlays/water_heating_overlay.py
index 3ec952de2..290182c50 100644
--- a/domain/epc/property_overlays/water_heating_overlay.py
+++ b/domain/epc/property_overlays/water_heating_overlay.py
@@ -26,6 +26,10 @@ _WATER_HEATING_CODES: dict[str, tuple[int, int]] = {
     "From main system, LPG (bulk)": (901, 27),
     "From main system, bottled LPG": (901, 3),
     "From main system, house coal": (901, 33),
+    # Wood logs — RdSAP water_heating_fuel 6 (biomass ~0.028 kgCO2/kWh), from
+    # main (901). A wood-fired individual-main dwelling's DHW must not fall to
+    # house coal 33 (~0.395), a ~14x carbon overstatement (ADR-0043).
+    "From main system, wood logs": (901, 6),
     "Electric immersion, electricity": (903, 29),
     # "boiler/circulator for water heating only" — SAP Table 4a code 911 (gas).
     "Gas boiler/circulator, mains gas": (911, 26),
diff --git a/domain/epc/property_overrides/water_heating_type.py b/domain/epc/property_overrides/water_heating_type.py
index e85a195d8..32e929acb 100644
--- a/domain/epc/property_overrides/water_heating_type.py
+++ b/domain/epc/property_overrides/water_heating_type.py
@@ -21,6 +21,7 @@ class WaterHeatingType(Enum):
     FROM_MAIN_LPG_BULK = "From main system, LPG (bulk)"
     FROM_MAIN_BOTTLED_LPG = "From main system, bottled LPG"
     FROM_MAIN_HOUSE_COAL = "From main system, house coal"
+    FROM_MAIN_WOOD_LOGS = "From main system, wood logs"
     ELECTRIC_IMMERSION = "Electric immersion, electricity"
     GAS_BOILER_CIRCULATOR_MAINS_GAS = "Gas boiler/circulator, mains gas"
     UNKNOWN = "Unknown"