diff --git a/landscape.c b/landscape.c
--- a/landscape.c
+++ b/landscape.c
@@ -246,14 +246,17 @@ bool hasFoundation(TileInfo *ti, bool di
 {
 	bool south, other; // southern corner and east/west corner
 	uint slope = _tile_type_procs[ti->type]->get_slope_tileh_proc(ti);
-	south = ((ti->tileh) & 2) != (slope & 2);
+	uint tileh = ti->tileh;
+
+	if(slope==0 && slope!=tileh) tileh=15;
+	south = (tileh & 2) != (slope & 2);
 
 	if(direction)
-		other = ((ti->tileh) & 4) != (slope & 4);
+		other = (tileh & 4) != (slope & 4);
 	else
-		other = ((ti->tileh) & 1) != (slope & 1);
+		other = (tileh & 1) != (slope & 1);
+	return south || other;
 
-	return south || other;
 }
 
 void DrawFoundation(TileInfo *ti, uint f)