diff --git a/src/Mod/Arch/ArchRoof.py b/src/Mod/Arch/ArchRoof.py
index f2e3d677dd..399958bb9d 100644
--- a/src/Mod/Arch/ArchRoof.py
+++ b/src/Mod/Arch/ArchRoof.py
@@ -177,6 +177,7 @@ class _Roof(ArchComponent.Component):
         obj.addProperty("App::PropertyInteger","Face","Base",        QT_TRANSLATE_NOOP("App::Property","The face number of the base object used to build this roof"))
         obj.addProperty("App::PropertyLength","RidgeLength","Arch",  QT_TRANSLATE_NOOP("App::Property","The total length of ridges and hips of this roof"))
         obj.addProperty("App::PropertyLength","BorderLength","Arch", QT_TRANSLATE_NOOP("App::Property","The total length of borders of this roof"))
+        obj.addProperty("App::PropertyBool","Flip","Arch",QT_TRANSLATE_NOOP("App::Property","Flip the roof direction if going the wrong way"))
         self.Type = "Roof"
         obj.Proxy = self
         obj.setEditorMode("RidgeLength",1)
@@ -200,6 +201,9 @@ class _Roof(ArchComponent.Component):
     def getPerpendicular(self, vec, rotEdge, l):
         " Get the perpendicular vec of given edge on xy plane "
         norm = FreeCAD.Vector(0,0,1)
+        if hasattr(self,"normal"):
+            if self.normal:
+                norm = FreeCAD.Vector(self.normal)
         perpendicular = vec.cross(norm)
         if  -180. <= rotEdge < -90.:
             perpendicular[0] = abs(perpendicular[0])*-1
@@ -218,6 +222,9 @@ class _Roof(ArchComponent.Component):
         perpendicular[2] = abs(perpendicular[2])
         perpendicular.normalize()
         perpendicular = perpendicular.multiply(l)
+        if hasattr(self,"flip"):
+            if self.flip:
+                return perpendicular.negative()
         return perpendicular
 
     def makeRoofProfilsDic(self, id, angle, run, idrel, overhang, thickness,):
@@ -518,7 +525,10 @@ class _Roof(ArchComponent.Component):
         import Part, math, DraftGeomUtils
         pl = obj.Placement
         #self.baseface = None
-
+        self.flip = False
+        if hasattr(obj,"Flip"):
+            if obj.Flip:
+                self.flip = True
         base = None
         w = None
         if obj.Base: