diff --git a/backend/documents_parser/elmhurst_extractor.py b/backend/documents_parser/elmhurst_extractor.py
index 0f440f4a..16f32e07 100644
--- a/backend/documents_parser/elmhurst_extractor.py
+++ b/backend/documents_parser/elmhurst_extractor.py
@@ -269,8 +269,8 @@ class ElmhurstSiteNotesExtractor:
         )
 
     def _wall_details_from_lines(self, lines: List[str]) -> WallDetails:
-        thickness_raw = self._local_val(lines, "Wall Thickness")
-        thickness_mm = (
+        thickness_raw: Optional[str] = self._local_val(lines, "Wall Thickness")
+        thickness_mm: Optional[int] = (
             int(thickness_raw.split()[0]) if thickness_raw else None
         )
         # Composite / retrofit insulation thickness — Summary §7.0
@@ -280,8 +280,8 @@ class ElmhurstSiteNotesExtractor:
         # is local-scoped inside the §7 block so it does not collide
         # with the §8 Roofs / §9 Floors blocks. None when the PDF
         # omits the line (no retrofit lodged).
-        ins_thickness_raw = self._local_val(lines, "Insulation Thickness")
-        insulation_thickness_mm = self._parse_thickness_mm(ins_thickness_raw)
+        ins_thickness_raw: Optional[str] = self._local_val(lines, "Insulation Thickness")
+        insulation_thickness_mm: Optional[int] = self._parse_thickness_mm(ins_thickness_raw)
         return WallDetails(
             wall_type=self._local_str(lines, "Type"),
             insulation=self._local_str(lines, "Insulation"),
@@ -318,8 +318,10 @@ class ElmhurstSiteNotesExtractor:
                 continue
             if area <= 0:
                 continue
-            thickness_raw = self._local_val(lines, f"Alternative Wall {n} Thickness")
-            thickness_mm = self._parse_thickness_mm(thickness_raw)
+            thickness_raw: Optional[str] = self._local_val(
+                lines, f"Alternative Wall {n} Thickness"
+            )
+            thickness_mm: Optional[int] = self._parse_thickness_mm(thickness_raw)
             result.append(AlternativeWall(
                 area_m2=area,
                 wall_type=self._local_str(lines, f"Alternative Wall {n} Type"),
@@ -365,8 +367,8 @@ class ElmhurstSiteNotesExtractor:
         return int(match.group()) if match else None
 
     def _roof_details_from_lines(self, lines: List[str]) -> RoofDetails:
-        thickness_raw = self._local_val(lines, "Insulation Thickness")
-        thickness_mm = self._parse_thickness_mm(thickness_raw)
+        thickness_raw: Optional[str] = self._local_val(lines, "Insulation Thickness")
+        thickness_mm: Optional[int] = self._parse_thickness_mm(thickness_raw)
         insulation = self._local_str(lines, "Insulation")
         # The Summary PDF omits the "Insulation Thickness" line entirely
         # when no retrofit insulation is lodged (e.g. "Insulation: N None"
@@ -390,14 +392,14 @@ class ElmhurstSiteNotesExtractor:
         return self._roof_details_from_lines(lines)
 
     def _floor_details_from_lines(self, lines: List[str]) -> FloorDetails:
-        u_val_raw = self._local_val(lines, "Default U-value")
-        default_u = float(u_val_raw) if u_val_raw else None
+        u_val_raw: Optional[str] = self._local_val(lines, "Default U-value")
+        default_u: Optional[float] = float(u_val_raw) if u_val_raw else None
         # RdSAP 10 §5.13 Table 20 — retro-fitted upper floors lodge an
         # "Insulation Thickness: NNN mm" cell so the cascade can route
         # via the per-thickness column. Mirror of the §8 roof extractor
         # at `_roof_details_from_lines`.
-        thickness_raw = self._local_val(lines, "Insulation Thickness")
-        thickness_mm = self._parse_thickness_mm(thickness_raw)
+        thickness_raw: Optional[str] = self._local_val(lines, "Insulation Thickness")
+        thickness_mm: Optional[int] = self._parse_thickness_mm(thickness_raw)
         return FloorDetails(
             location=self._local_str(lines, "Location"),
             floor_type=self._local_str(lines, "Type"),