diff --git a/src/blenderbim/blenderbim/bim/module/model/wall.py b/src/blenderbim/blenderbim/bim/module/model/wall.py
index 4cfbe60653..0be02b718a 100644
--- a/src/blenderbim/blenderbim/bim/module/model/wall.py
+++ b/src/blenderbim/blenderbim/bim/module/model/wall.py
@@ -924,15 +924,19 @@ class DumbWallPlaner:
         IfcStore.edited_objs.add(obj)
 
     def thicken_face(self, face, delta_thickness):
-        slide_magnitude = abs(delta_thickness) / 2
+        slide_magnitude = abs(delta_thickness)
         for vert in face.verts:
             slide_vector = None
             for edge in vert.link_edges:
                 other_vert = edge.verts[1] if edge.verts[0] == vert else edge.verts[0]
                 if delta_thickness > 0:
                     potential_slide_vector = vert.co - other_vert.co
+                    if potential_slide_vector.y < 0:
+                        continue
                 else:
                     potential_slide_vector = other_vert.co - vert.co
+                    if potential_slide_vector.y > 0:
+                        continue
                 if abs(potential_slide_vector.x) > 0.9 or abs(potential_slide_vector.z) > 0.9:
                     continue
                 slide_vector = potential_slide_vector