diff --git a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
index f89c4c72..a495addd 100644
--- a/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
+++ b/backend/documents_parser/tests/test_summary_pdf_mapper_chain.py
@@ -1540,6 +1540,23 @@ def test_summary_mapper_raises_on_unmapped_cylinder_insulation_label() -> None:
     assert excinfo.value.value == "Polyester wool"
 
 
+def test_elmhurst_glazing_type_code_strips_interleaved_alternative_wall() -> None:
+    # Arrange — when a property lodges an Alternative Wall (cert 001431
+    # storage-heater variants, "simulated case 34"), pdftotext interleaves
+    # the §11 "Alternative wall 1" location column into the wrapped
+    # glazing-type cell, e.g. "Double between 2002 Alternative wall and 2021
+    # 1 Alternative wall". The wall-location fragments are not part of the
+    # glazing type — the helper must recover "Double between 2002 and 2021".
+
+    # Act
+    code = _elmhurst_glazing_type_code(
+        "Double between 2002 Alternative wall and 2021 1 Alternative wall"
+    )
+
+    # Assert
+    assert code == _elmhurst_glazing_type_code("Double between 2002 and 2021")
+
+
 def test_elmhurst_immersion_type_code_maps_dual_and_single() -> None:
     # Arrange — Elmhurst Summary §15.1 "Immersion Heater" lodges "Dual"
     # or "Single". RdSAP 10 §10.5 (PDF p.54): an immersion is "assumed
diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index e5c794c8..d6573aac 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -5470,6 +5470,21 @@ _ELMHURST_GLAZING_LABEL_TRAILING_GAP_RE: Final[re.Pattern[str]] = re.compile(
 _ELMHURST_GLAZING_LABEL_TRAILING_BP_RE: Final[re.Pattern[str]] = re.compile(
     r"\s+(?:\d+(?:st|nd|rd|th)|Main)$"
 )
+# Fallback only: when a property lodges an Alternative Wall, pdftotext
+# INTERLEAVES the §11 location column ("Alternative wall 1") into the
+# wrapped glazing-TYPE cell, e.g. "Double between 2002 Alternative wall
+# and 2021 1 Alternative wall" (cert 001431 storage-heater variants,
+# `simulated case 34`). The greedy trailing-suffix strip truncates at the
+# first "Alternative wall" (losing "and 2021"), so remove EVERY
+# wall-location fragment + any stray 1-2 digit location index globally and
+# retry. Loss-free: no glazing-type key contains a wall-location phrase or
+# a bare 1-2 digit number (install-date years are 4 digits).
+_ELMHURST_GLAZING_LABEL_EMBEDDED_WALL_RE: Final[re.Pattern[str]] = re.compile(
+    r"\s*(?:External|Alternative|Party)\s+wall(?:\s+\d+)?"
+)
+_ELMHURST_GLAZING_LABEL_STRAY_LOCATION_DIGIT_RE: Final[re.Pattern[str]] = re.compile(
+    r"\b\d{1,2}\b"
+)
 
 
 def _elmhurst_glazing_type_code(label: Optional[str]) -> int:
@@ -5501,6 +5516,18 @@ def _elmhurst_glazing_type_code(label: Optional[str]) -> int:
         code = _ELMHURST_GLAZING_LABEL_TO_SAP10.get(debp)
         if code is not None:
             return code
+    # Fallback: remove INTERLEAVED wall-location fragments from the raw
+    # label (Alternative/External/Party wall + stray location index) and
+    # collapse whitespace. Operates on `label`, not the greedily-truncated
+    # `cleaned`, so "Double between 2002 ... and 2021" survives.
+    dewall = _ELMHURST_GLAZING_LABEL_EMBEDDED_WALL_RE.sub(" ", label)
+    dewall = _ELMHURST_GLAZING_LABEL_STRAY_LOCATION_DIGIT_RE.sub(" ", dewall)
+    dewall = _ELMHURST_GLAZING_LABEL_NOISE_PREFIX_RE.sub("", dewall)
+    dewall = re.sub(r"\s+", " ", dewall).strip()
+    if dewall != cleaned:
+        code = _ELMHURST_GLAZING_LABEL_TO_SAP10.get(dewall)
+        if code is not None:
+            return code
     raise UnmappedElmhurstLabel("glazing_type", label)