diff --git a/api/additional_endpoints.yaml b/api/additional_endpoints.yaml
new file mode 100644
index 0000000..123d1f8
--- /dev/null
+++ b/api/additional_endpoints.yaml
@@ -0,0 +1,29 @@
+# -------------------------------------------------------------------
+# ATTENTION: This file will not be parsed by Cheetah
+#            Use plain openapi/yaml syntax, no Cheetah
+#            escaping
+# -------------------------------------------------------------------
+
+
+  /v1/overhead_advance_flat_mappings/flat/{flatId}:
+    get:
+      tags: [ "overhead_advance_flat_mapping", "flat" ]
+      summary: Returns all overhead advance mappings for a given flat
+      operationId: additional_methods.get_overhead_advance_flat_mapping_by_flat
+      parameters:
+        - name: flatId
+          in: path
+          required: true
+          schema:
+            type: integer
+      responses:
+        '200':
+          description: $table.name response
+          content:
+            'application/json':
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/overhead_advance_flat_mapping'
+      security:
+      - jwt: ['secret']
diff --git a/api/additional_methods.py b/api/additional_methods.py
new file mode 100644
index 0000000..133d3ac
--- /dev/null
+++ b/api/additional_methods.py
@@ -0,0 +1,19 @@
+from db import dbGetMany, dbGetOne, dbInsert, dbUpdate
+from loguru import logger
+import werkzeug
+
+
+def get_overhead_advance_flat_mapping_by_flat(user, token_info, flatId=None):
+    return dbGetOne(user, token_info, {
+            "statement": """
+SELECT 
+  id
+  ,overhead_advance
+  ,flat
+  FROM overhead_advance_flat_mapping_t
+  WHERE flat = %s
+                         """, 
+            "params": (flatId, )
+        }
+    )
+
diff --git a/api/openapi.yaml b/api/openapi.yaml
index 2e5fc3e..cffd251 100644
--- a/api/openapi.yaml
+++ b/api/openapi.yaml
@@ -971,6 +971,36 @@ paths:
       security:
       - jwt: ['secret']
 
+# -------------------------------------------------------------------
+# ATTENTION: This file will not be parsed by Cheetah
+#            Use plain openapi/yaml syntax, no Cheetah
+#            escaping
+# -------------------------------------------------------------------
+
+
+  /v1/overhead_advance_flat_mappings/flat/{flatId}:
+    get:
+      tags: [ "overhead_advance_flat_mapping", "flat" ]
+      summary: Returns all overhead advance mappings for a given flat
+      operationId: additional_methods.get_overhead_advance_flat_mapping_by_flat
+      parameters:
+        - name: flatId
+          in: path
+          required: true
+          schema:
+            type: integer
+      responses:
+        '200':
+          description: $table.name response
+          content:
+            'application/json':
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/overhead_advance_flat_mapping'
+      security:
+      - jwt: ['secret']
+
 components:
   securitySchemes:
     jwt:
diff --git a/api/openapi.yaml.tmpl b/api/openapi.yaml.tmpl
index 87f1074..697da27 100644
--- a/api/openapi.yaml.tmpl
+++ b/api/openapi.yaml.tmpl
@@ -105,6 +105,8 @@ paths:
 #end if
 #end for
 
+#include raw "./api/additional_endpoints.yaml"
+
 components:
   securitySchemes:
     jwt: