diff --git a/backend/documents_parser/tests/fixtures/Summary_001431_case44.pdf b/backend/documents_parser/tests/fixtures/Summary_001431_case44.pdf
new file mode 100644
index 00000000..4312e6c1
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_001431_case44.pdf differ
diff --git a/domain/sap10_calculator/worksheet/conservatory.py b/domain/sap10_calculator/worksheet/conservatory.py
new file mode 100644
index 00000000..b9729e1f
--- /dev/null
+++ b/domain/sap10_calculator/worksheet/conservatory.py
@@ -0,0 +1,149 @@
+"""RdSAP 10 §6.1 — non-separated (heated) conservatory geometry.
+
+A non-separated conservatory is treated as part of the dwelling
+(RdSAP 10 Specification, 9th June 2025, §6.1 + Table 25, pages 49-51):
+
+  - its floor area and volume are added to TFA (4) and volume (5);
+  - its fully-glazed walls bill as a window — line (27) — at the Table 25
+    "U-value of window"; its glazed roof bills as a rooflight — line (27a)
+    — at the Table 25 "U-value of roof window"; both U-values already
+    include the §3.2 curtain resistance (R=0.04 m²K/W);
+  - its floor adds a ground-loss term — line (28a) — via BS EN ISO 13370,
+    taken as an uninsulated solid floor with 300 mm walls (§5.12 note,
+    spec p.43), exposed perimeter = glazed perimeter;
+  - its glazed wall + glazed roof + floor areas count toward the total
+    exposed area (31) and hence thermal bridging (36); the fully-glazed
+    "structure" walls/roof themselves add nothing (the glazing IS the
+    window/rooflight).
+
+Its roof area is the floor area / cos(20°) and its wall area is the
+exposed perimeter × height; the height is translated from the lodged
+equivalent storey count (§6.1): 1 storey → ground-floor room height;
+1½ → ground + 0.25 + 0.5×first; 2 → ground + 0.25 + first; etc.
+
+A SEPARATED conservatory (§6.2) is disregarded entirely — the mapper
+maps it to None, so it never reaches this module.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from decimal import Decimal, ROUND_HALF_UP
+from math import cos, radians
+from typing import Final, Optional
+
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+
+# RdSAP 10 §6.1 — conservatory roof area = floor area / cos(20°); §6.1
+# also fixes the rooflight solar pitch at 20°.
+CONSERVATORY_ROOF_PITCH_DEG: Final[float] = 20.0
+_COS_ROOF_PITCH: Final[float] = cos(radians(CONSERVATORY_ROOF_PITCH_DEG))
+
+# RdSAP 10 Table 25 (PDF p.51) — default conservatory glazing U-values
+# (W/m²K, INCLUSIVE of the §3.2 curtain resistance) and g-values. The
+# Summary lodges only double vs single (no triple), so a bool selects the
+# row: True → double (6 mm gap), False → single.
+_TABLE_25_WALL_U: Final[dict[bool, float]] = {True: 3.1, False: 4.8}
+_TABLE_25_ROOF_U: Final[dict[bool, float]] = {True: 3.4, False: 5.3}
+_TABLE_25_G_VALUE: Final[dict[bool, float]] = {True: 0.76, False: 0.85}
+_TABLE_25_FRAME_FACTOR: Final[float] = 0.70  # Table 25 — wood/PVC frame
+
+# SAP 10.2 §3.2 formula (2) curtain/blind resistance. Table 25 U-values
+# are "adjusted for curtains" already, so the EFFECTIVE conduction U is
+# 1 / (1/U_table25 + 0.04) — the same transform `heat_transmission`
+# applies to regular windows/rooflights.
+_CURTAIN_RESISTANCE_M2K_PER_W: Final[float] = 0.04
+
+# RdSAP 10 §5.12 (spec p.43) — a non-separated conservatory floor is an
+# uninsulated solid ground floor with 300 mm walls.
+_CONSERVATORY_WALL_THICKNESS_MM: Final[int] = 300
+_AREA_ROUND_DP: Final[int] = 2
+
+
+def _round2(value: float) -> float:
+    """RdSAP 10 §15 (p.66): element areas + conservatory height → 2 d.p."""
+    return float(
+        Decimal(str(value)).quantize(Decimal("0.01"), rounding=ROUND_HALF_UP)
+    )
+
+
+@dataclass(frozen=True)
+class ConservatoryGeometry:
+    """Derived §6.1 geometry for one non-separated conservatory. Areas and
+    height are rounded to 2 d.p. per RdSAP 10 §15."""
+
+    height_m: float
+    floor_area_m2: float
+    glazed_wall_area_m2: float
+    glazed_roof_area_m2: float
+    glazed_perimeter_m: float
+    wall_u_raw: float          # Table 25 window U, pre-curtain
+    roof_u_raw: float          # Table 25 roof-window U, pre-curtain
+    wall_u_eff: float          # post-curtain conduction U for line (27)
+    roof_u_eff: float          # post-curtain conduction U for line (27a)
+    g_value: float
+    frame_factor: float
+    volume_m3: float
+
+
+def _conservatory_height_m(epc: EpcPropertyData, storeys: float) -> float:
+    """Translate the equivalent storey count into a metre height per
+    RdSAP 10 §6.1 using the dwelling's per-storey room heights:
+
+      1 storey  → ground-floor room height
+      1½ storey → ground + 0.25 + 0.5 × first-floor room height
+      2 storey  → ground + 0.25 + first-floor room height
+      etc.
+
+    Room heights are taken from the Main building part's floor
+    dimensions (floor 0 = ground, 1 = first, ...). Returns 0.0 when no
+    storeys are lodged (defensive; the conservatory then bills no walls)."""
+    parts = epc.sap_building_parts or []
+    heights: list[float] = []
+    if parts:
+        fds = sorted(
+            parts[0].sap_floor_dimensions,
+            key=lambda fd: fd.floor if fd.floor is not None else 0,
+        )
+        heights = [fd.room_height_m for fd in fds if fd.room_height_m]
+    if not heights:
+        return 0.0
+    n_full = int(storeys)
+    height = heights[0]
+    for s in range(1, n_full):
+        height += 0.25 + heights[min(s, len(heights) - 1)]
+    if storeys - n_full >= 0.5:
+        height += 0.25 + 0.5 * heights[min(n_full, len(heights) - 1)]
+    return _round2(height)
+
+
+def conservatory_geometry(
+    epc: EpcPropertyData,
+) -> Optional[ConservatoryGeometry]:
+    """Build the §6.1 conservatory geometry, or None when there is no
+    (non-separated) conservatory."""
+    cons = epc.sap_conservatory
+    if cons is None or cons.thermally_separated:
+        return None
+    height = _conservatory_height_m(epc, cons.room_height_storeys)
+    floor_area = cons.floor_area_m2
+    glazed_perimeter = cons.glazed_perimeter_m
+    glazed_wall = _round2(glazed_perimeter * height)
+    glazed_roof = _round2(floor_area / _COS_ROOF_PITCH)
+    dg = cons.double_glazed
+    wall_u_raw = _TABLE_25_WALL_U[dg]
+    roof_u_raw = _TABLE_25_ROOF_U[dg]
+    return ConservatoryGeometry(
+        height_m=height,
+        floor_area_m2=floor_area,
+        glazed_wall_area_m2=glazed_wall,
+        glazed_roof_area_m2=glazed_roof,
+        glazed_perimeter_m=glazed_perimeter,
+        wall_u_raw=wall_u_raw,
+        roof_u_raw=roof_u_raw,
+        wall_u_eff=1.0 / (1.0 / wall_u_raw + _CURTAIN_RESISTANCE_M2K_PER_W),
+        roof_u_eff=1.0 / (1.0 / roof_u_raw + _CURTAIN_RESISTANCE_M2K_PER_W),
+        g_value=_TABLE_25_G_VALUE[dg],
+        frame_factor=_TABLE_25_FRAME_FACTOR,
+        volume_m3=floor_area * height,
+    )
diff --git a/domain/sap10_calculator/worksheet/dimensions.py b/domain/sap10_calculator/worksheet/dimensions.py
index f48e24d5..792770b4 100644
--- a/domain/sap10_calculator/worksheet/dimensions.py
+++ b/domain/sap10_calculator/worksheet/dimensions.py
@@ -21,6 +21,7 @@ from dataclasses import dataclass
 from typing import Final
 
 from datatypes.epc.domain.epc_property_data import EpcPropertyData, SapBuildingPart
+from domain.sap10_calculator.worksheet.conservatory import conservatory_geometry
 
 _DEFAULT_STOREY_HEIGHT_M: Final[float] = 2.5
 
@@ -145,17 +146,28 @@ def dimensions_from_cert(epc: EpcPropertyData) -> Dimensions:
     total_storey_count = max(part_storey_counts) if part_storey_counts else 0
 
     has_storeys = sum_per_storey_area_m2 > 0
+    # `avg_height` (used by §2 (9) dwelling height → infiltration) is a
+    # property of the dwelling's storeys, so the conservatory is excluded
+    # from it. The conservatory IS added to TFA (4) and volume (5) per
+    # RdSAP 10 §6.1 ("The floor area and volume of a non-separated
+    # conservatory are added to the total floor area and volume of the
+    # dwelling") — it just doesn't form a storey.
     avg_height = (
         sum_per_storey_volume_m3 / sum_per_storey_area_m2
         if has_storeys
         else _DEFAULT_STOREY_HEIGHT_M
     )
+    cons = conservatory_geometry(epc)
+    cons_floor_area_m2 = cons.floor_area_m2 if cons is not None else 0.0
+    cons_volume_m3 = cons.volume_m3 if cons is not None else 0.0
     return Dimensions(
         total_floor_area_m2=(
-            sum_per_storey_area_m2 if has_storeys else epc.total_floor_area_m2
+            sum_per_storey_area_m2 + cons_floor_area_m2
+            if has_storeys
+            else epc.total_floor_area_m2
         ),
         volume_m3=(
-            sum_per_storey_volume_m3
+            sum_per_storey_volume_m3 + cons_volume_m3
             if has_storeys
             else epc.total_floor_area_m2 * _DEFAULT_STOREY_HEIGHT_M
         ),
diff --git a/domain/sap10_calculator/worksheet/heat_transmission.py b/domain/sap10_calculator/worksheet/heat_transmission.py
index 83668e6f..4d2971d8 100644
--- a/domain/sap10_calculator/worksheet/heat_transmission.py
+++ b/domain/sap10_calculator/worksheet/heat_transmission.py
@@ -71,6 +71,7 @@ from domain.sap10_ml.rdsap_uvalues import (
     u_wall,
     u_window,
 )
+from domain.sap10_calculator.worksheet.conservatory import conservatory_geometry
 from math import cos, floor, radians, sqrt
 
 
@@ -123,6 +124,9 @@ _DEFAULT_DOOR_AREA_M2: Final[float] = 1.85
 # deducts from that wall, not the main wall.
 _CORRIDOR_DOOR_U_W_PER_M2K: Final[float] = 1.4
 _DEFAULT_STOREY_HEIGHT_M: Final[float] = 2.5
+# RdSAP 10 §5.12 (spec p.43) — a non-separated conservatory floor is an
+# uninsulated solid ground floor with 300 mm walls.
+_CONSERVATORY_WALL_THICKNESS_MM: Final[int] = 300
 # SAP10.2 §3.2 curtain/blind thermal resistance applied to windows (and
 # roof windows) — turns raw window U into the worksheet's (27) effective U.
 _WINDOW_CURTAIN_RESISTANCE_M2K_PER_W: Final[float] = 0.04
@@ -1368,6 +1372,51 @@ def heat_transmission_from_cert(
     # door line.
     doors += _CORRIDOR_DOOR_U_W_PER_M2K * corridor_door_area
     roof_windows_w_per_k = roof_windows_w_per_k_total
+
+    # RdSAP 10 §6.1 (PDF p.49) + Table 25 (p.51) — a non-separated
+    # conservatory. Its fully-glazed walls bill as a window (27), its
+    # glazed roof as a rooflight (27a), and its floor adds a ground-loss
+    # term (28a) via BS EN ISO 13370 (uninsulated solid floor, 300 mm
+    # walls per §5.12; exposed perimeter = glazed perimeter). The glazed
+    # wall + roof + floor areas join (31)/(36) external area; the fully-
+    # glazed "structure" walls/roof add nothing (the glazing IS the
+    # window/rooflight). A separated conservatory (§6.2) is mapped to
+    # None upstream and never reaches here.
+    cons_geom = conservatory_geometry(epc)
+    cons_windows_w_per_k: float = 0.0
+    if cons_geom is not None:
+        cons_windows_w_per_k = (
+            cons_geom.glazed_wall_area_m2 * cons_geom.wall_u_eff
+        )
+        roof_windows_w_per_k += (
+            cons_geom.glazed_roof_area_m2 * cons_geom.roof_u_eff
+        )
+        u_cons_floor = u_floor(
+            country=country,
+            age_band=primary_age,
+            construction=None,
+            insulation_thickness_mm=0,
+            area_m2=cons_geom.floor_area_m2,
+            perimeter_m=cons_geom.glazed_perimeter_m,
+            wall_thickness_mm=_CONSERVATORY_WALL_THICKNESS_MM,
+            # Force the solid-floor branch of BS EN ISO 13370 regardless of
+            # age band (§5.12: conservatory floor is an uninsulated SOLID
+            # ground floor — the A/B suspended-timber default must not fire).
+            description="Solid",
+        )
+        floor += u_cons_floor * cons_geom.floor_area_m2
+        cons_external_area = (
+            cons_geom.glazed_wall_area_m2
+            + cons_geom.glazed_roof_area_m2
+            + cons_geom.floor_area_m2
+        )
+        total_external_area += cons_external_area
+        bridging += dwelling_y * cons_external_area
+    # Fold the conservatory glazed wall into the (27) window readout. The
+    # `windows` accumulator is partially-typed upstream (the per-window
+    # `u_value` arrives as `Any`); `float(...)` re-asserts the strict float
+    # type as we add the strictly-typed conservatory term.
+    windows = float(windows) + cons_windows_w_per_k
     fabric_heat_loss = (
         walls + roof + floor + party + windows + roof_windows_w_per_k + doors  # (33)
     )
diff --git a/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_001431_case44.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_001431_case44.py
new file mode 100644
index 00000000..39d7da49
--- /dev/null
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_001431_case44.py
@@ -0,0 +1,119 @@
+"""Mapper-driven cascade pin against the Elmhurst P960-0001-001431
+"simulated case 44" worksheet — a 2-storey mid-terrace with a NON-SEPARATED
+(heated, type-4) DOUBLE-glazed CONSERVATORY.
+
+Case 44 is the 1e-4 oracle for RdSAP 10 §6.1 (PDF p.49) + Table 25 (p.51).
+The Summary §5 lodges: Floor Area 12.00 m², Glazed Perimeter 9.00 m,
+Double Glazed Yes, thermally separated No, Room Height 1 Storey. From that
+the §6.1 cascade derives (all verified against the P960 §3 to 1e-4):
+
+  - conservatory height = ground-floor room height = 2.60 m (1 storey);
+  - glazed WALL → window (27): A = perimeter × height = 9.0 × 2.60 = 23.40,
+    U = 1/(1/3.1 + 0.04) = 2.758 (Table 25 double 3.1 + §3.2 curtain);
+  - glazed ROOF → rooflight (27a): A = floor_area / cos(20°) = 12.77,
+    U = 1/(1/3.4 + 0.04) = 2.993 (Table 25 roof 3.4 + curtain);
+  - FLOOR → ground floor (28a): A = 12.00, U = 0.89 via BS EN ISO 13370
+    (uninsulated solid, 300 mm walls, P = glazed perimeter 9.0);
+  - the fully-glazed structure walls/roof bill at U=0 (the glazing IS the
+    window/rooflight) — they contribute nothing but DO count their glazed
+    area toward (31)/(36);
+  - TFA (4) += 12.00 → 95.38; volume (5) += 12.00 × 2.60 = 31.20 → 257.16.
+
+Like the other `_elmhurst_worksheet_001431_case*` fixtures this does NOT
+hand-build the EpcPropertyData: it routes the Summary PDF through
+ElmhurstSiteNotesExtractor + from_elmhurst_site_notes so the pin exercises
+the WHOLE extractor + mapper + calculator pipeline.
+
+Source: user-simulated PDFs at `sap worksheets/golden fixture debugging/
+simulated case 44/`. The Summary is mirrored into the tracked
+`backend/documents_parser/tests/fixtures/Summary_001431_case44.pdf` so the
+test runs without depending on the unstaged workspace.
+
+Worksheet pin targets (P960-0001-001431, "11a. SAP rating" UK-average
+rating block our cascade reproduces):
+- (4)   TFA, m²                                = 95.3800
+- (5)   Dwelling volume, m³                     = 257.1630
+- (27)  Windows (31.5795 main + 64.5374 cons)   = 96.1169
+- (27a) Roof windows (conservatory glazed roof) = 38.2201
+- (28a) Ground floor (10.7364 main + 10.6800)   = 21.4164
+- (29a) External walls                          = 35.5852
+- (30)  External roof                           = 7.4688
+- (31)  Total net area of external elements     = 294.2900
+- (33)  Fabric heat loss, W/K                    = 207.3274
+- (36)  Thermal bridges (0.080 × (31))           = 23.5432
+
+Per [[feedback-zero-error-strict]]: pins are abs <= 1e-4 against the PDF.
+"""
+
+from __future__ import annotations
+
+import re
+import subprocess
+from pathlib import Path
+from typing import Final
+
+from backend.documents_parser.elmhurst_extractor import ElmhurstSiteNotesExtractor
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+
+# parents[0]=worksheet/, [1]=sap10_calculator/, [2]=domain/, [3]=tests/,
+# [4]=repo root.
+_SUMMARY_PDF: Final[Path] = (
+    Path(__file__).resolve().parents[4]
+    / "backend" / "documents_parser" / "tests" / "fixtures"
+    / "Summary_001431_case44.pdf"
+)
+
+LINE_4_TFA_M2: Final[float] = 95.3800
+LINE_5_VOLUME_M3: Final[float] = 257.1630
+LINE_27_WINDOWS_W_PER_K: Final[float] = 96.1169
+LINE_27A_ROOF_WINDOWS_W_PER_K: Final[float] = 38.2201
+LINE_28A_FLOOR_W_PER_K: Final[float] = 21.4164
+LINE_29A_WALLS_W_PER_K: Final[float] = 35.5852
+LINE_30_ROOF_W_PER_K: Final[float] = 7.4688
+LINE_31_EXTERNAL_AREA_M2: Final[float] = 294.2900
+LINE_33_FABRIC_W_PER_K: Final[float] = 207.3274
+LINE_36_THERMAL_BRIDGING_W_PER_K: Final[float] = 23.5432
+
+
+def _summary_pdf_to_textract_style_pages(pdf_path: Path) -> list[str]:
+    """Convert a Summary PDF into the per-page text format the
+    ElmhurstSiteNotesExtractor expects (label/value token sequences).
+    Mirror of the helper in the other `_elmhurst_worksheet_*` fixtures.
+    """
+    info = subprocess.run(
+        ["pdfinfo", str(pdf_path)], capture_output=True, text=True, check=True,
+    ).stdout
+    m = re.search(r"Pages:\s+(\d+)", info)
+    if m is None:
+        raise RuntimeError(f"Could not parse page count from {pdf_path}")
+    page_count = int(m.group(1))
+    pages: list[str] = []
+    for i in range(1, page_count + 1):
+        layout = subprocess.run(
+            [
+                "pdftotext", "-layout", "-f", str(i), "-l", str(i),
+                str(pdf_path), "-",
+            ],
+            capture_output=True, text=True, check=True,
+        ).stdout
+        tokens: list[str] = []
+        for line in layout.splitlines():
+            if not line.strip():
+                tokens.append("")
+                continue
+            parts = [p for p in re.split(r"\s{2,}", line.strip()) if p]
+            tokens.extend(parts)
+        pages.append("\n".join(tokens))
+    return pages
+
+
+def build_epc() -> EpcPropertyData:
+    """Route the simulated case-44 Summary through extractor + mapper.
+    No hand-built EpcPropertyData — the extractor and mapper are part of
+    the test target. This module is a pin PROVIDER (build_epc + LINE_*
+    constants); the collected assertions live in
+    `test_section_cascade_pins`."""
+    pages = _summary_pdf_to_textract_style_pages(_SUMMARY_PDF)
+    site_notes = ElmhurstSiteNotesExtractor(pages).extract()
+    return EpcPropertyDataMapper.from_elmhurst_site_notes(site_notes)
diff --git a/tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py b/tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py
index 4e7336e3..d4725df9 100644
--- a/tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py
+++ b/tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py
@@ -45,6 +45,7 @@ from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_001431_case6 as _w001431_case6,
     _elmhurst_worksheet_001431_case21 as _w001431_case21,
     _elmhurst_worksheet_001431_case43 as _w001431_case43,
+    _elmhurst_worksheet_001431_case44 as _w001431_case44,
 )
 
 
@@ -370,6 +371,62 @@ def test_case43_detailed_rr_dryline_and_mixed_roof_match_pdf() -> None:
     )
 
 
+def test_case44_non_separated_conservatory_fabric_matches_pdf() -> None:
+    """§3 fabric pin for simulated case 44 — a non-separated DOUBLE-glazed
+    conservatory (RdSAP 10 §6.1 + Table 25). The conservatory's glazed wall
+    bills as a window (27), its glazed roof as a rooflight (27a), its floor
+    adds a ground-loss term (28a), and its glazed wall + roof + floor areas
+    join (31)/(36); TFA (4) and volume (5) absorb its floor area + volume.
+    The main dwelling's walls (29a) / roof (30) are untouched — pinned to
+    guard against the conservatory leaking into the wrong element."""
+    # Arrange
+    epc = _w001431_case44.build_epc()
+
+    # Act
+    ht = heat_transmission_section_from_cert(epc)
+    dim = dimensions_from_cert(epc)
+
+    # Assert — §1 totals + §3 fabric, each at abs=1e-4.
+    _pin(dim.total_floor_area_m2, _w001431_case44.LINE_4_TFA_M2, "§1 (4) case44")
+    _pin(dim.volume_m3, _w001431_case44.LINE_5_VOLUME_M3, "§1 (5) case44")
+    _pin(
+        ht.windows_w_per_k,
+        _w001431_case44.LINE_27_WINDOWS_W_PER_K,
+        "§3 (27) case44",
+    )
+    _pin(
+        ht.roof_windows_w_per_k,
+        _w001431_case44.LINE_27A_ROOF_WINDOWS_W_PER_K,
+        "§3 (27a) case44",
+    )
+    _pin(
+        ht.floor_w_per_k,
+        _w001431_case44.LINE_28A_FLOOR_W_PER_K,
+        "§3 (28a) case44",
+    )
+    _pin(
+        ht.walls_w_per_k,
+        _w001431_case44.LINE_29A_WALLS_W_PER_K,
+        "§3 (29a) case44",
+    )
+    _pin(ht.roof_w_per_k, _w001431_case44.LINE_30_ROOF_W_PER_K, "§3 (30) case44")
+    _pin(
+        ht.total_external_element_area_m2,
+        _w001431_case44.LINE_31_EXTERNAL_AREA_M2,
+        "§3 (31) case44",
+    )
+    _pin(
+        ht.fabric_heat_loss_w_per_k,
+        _w001431_case44.LINE_33_FABRIC_W_PER_K,
+        "§3 (33) case44",
+    )
+    _pin(
+        ht.thermal_bridging_w_per_k,
+        _w001431_case44.LINE_36_THERMAL_BRIDGING_W_PER_K,
+        "§3 (36) case44",
+    )
+
+
 def test_case6_main_2_emitter_and_control_extracted() -> None:
     """Simulated case 6's §14.1 Main Heating2 lodges its OWN emitter
     ("Underfloor Heating") and control ("SAP code 2110, ...") — the two