diff --git a/packages/domain/src/domain/sap/calculator.py b/packages/domain/src/domain/sap/calculator.py
index 39f47d92..68b1f5c1 100644
--- a/packages/domain/src/domain/sap/calculator.py
+++ b/packages/domain/src/domain/sap/calculator.py
@@ -163,6 +163,7 @@ class SapResult:
     primary_energy_kwh_per_yr: float
     primary_energy_kwh_per_m2: float
     monthly: tuple[MonthlyEntry, ...]
+    intermediate: dict[str, float]
 
 
 def _solar_gains_w(
@@ -331,6 +332,12 @@ def calculate_sap_from_inputs(inputs: CalculatorInputs) -> SapResult:
     )
     primary_energy_per_m2 = primary_energy_kwh / tfa if tfa > 0 else 0.0
 
+    intermediate: dict[str, float] = {
+        "tfa_m2": inputs.dimensions.total_floor_area_m2,
+        "volume_m3": inputs.dimensions.volume_m3,
+        "storey_count": float(inputs.dimensions.storey_count),
+    }
+
     return SapResult(
         sap_score=sap_int,
         sap_score_continuous=sap_cont,
@@ -346,6 +353,7 @@ def calculate_sap_from_inputs(inputs: CalculatorInputs) -> SapResult:
         primary_energy_kwh_per_yr=primary_energy_kwh,
         primary_energy_kwh_per_m2=primary_energy_per_m2,
         monthly=monthly,
+        intermediate=intermediate,
     )
 
 
diff --git a/packages/domain/src/domain/sap/tests/test_calculator.py b/packages/domain/src/domain/sap/tests/test_calculator.py
index 5e17e07f..d3d0de47 100644
--- a/packages/domain/src/domain/sap/tests/test_calculator.py
+++ b/packages/domain/src/domain/sap/tests/test_calculator.py
@@ -124,6 +124,21 @@ def test_calculator_returns_twelve_month_breakdown_and_plausible_sap_score() ->
     )
 
 
+def test_calculate_exposes_dimensions_intermediates() -> None:
+    # Arrange — P5 trace mode: `result.intermediate` must surface the
+    # worksheet-named dimensions variables for per-section diffing
+    # against BRE worked examples and hand calcs (ADR-0010 / handover §11).
+    inputs = _baseline_inputs()
+
+    # Act
+    result = calculate_sap_from_inputs(inputs)
+
+    # Assert
+    assert result.intermediate["tfa_m2"] == inputs.dimensions.total_floor_area_m2
+    assert result.intermediate["volume_m3"] == inputs.dimensions.volume_m3
+    assert result.intermediate["storey_count"] == float(inputs.dimensions.storey_count)
+
+
 def test_higher_main_heating_efficiency_reduces_fuel_use() -> None:
     # Arrange — Direction check: doubling the boiler efficiency must halve
     # the main-heating fuel kWh, holding everything else constant.