diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index a1631ee2..95e48b45 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -2063,6 +2063,14 @@ class EpcPropertyDataMapper:
                     from_dict(RdSapSchema20_0_0, data)
                 )
             )
+        if schema == "RdSAP-Schema-18.0":
+            from datatypes.epc.schema.rdsap_schema_18_0 import RdSapSchema18_0
+
+            return _clear_basement_flag_when_system_built(
+                EpcPropertyDataMapper.from_rdsap_schema_18_0(
+                    from_dict(RdSapSchema18_0, data)
+                )
+            )
 
         raise ValueError(f"Unsupported EPC schema: {schema!r}")
 
diff --git a/datatypes/epc/schema/rdsap_schema_18_0.py b/datatypes/epc/schema/rdsap_schema_18_0.py
index 4ce2f887..0d798a35 100644
--- a/datatypes/epc/schema/rdsap_schema_18_0.py
+++ b/datatypes/epc/schema/rdsap_schema_18_0.py
@@ -1,4 +1,4 @@
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from typing import List, Optional, Union
 
 from .common import CostAmount, DescriptionV1, Measurement
@@ -159,7 +159,7 @@ class RenewableHeatIncentive:
     impact_of_solid_wall_insulation: Optional[int] = None
 
 
-@dataclass
+@dataclass(kw_only=True)
 class RdSapSchema18_0:
     uprn: int
     roofs: List[EnergyElement]
@@ -202,7 +202,7 @@ class RdSapSchema18_0:
     registration_date: str
     sap_energy_source: SapEnergySource
     secondary_heating: EnergyElement
-    lzc_energy_sources: List[int]
+    lzc_energy_sources: List[int] = field(default_factory=list)
     sap_building_parts: List[SapBuildingPart]
     low_energy_lighting: int
     solar_water_heating: str
@@ -221,7 +221,7 @@ class RdSapSchema18_0:
     hot_water_cost_current: CostAmount
     mechanical_ventilation: int
     percent_draughtproofed: int
-    suggested_improvements: List[SuggestedImprovement]
+    suggested_improvements: List[SuggestedImprovement] = field(default_factory=list)
     co2_emissions_potential: float
     energy_rating_potential: int
     lighting_cost_potential: CostAmount