diff --git a/src/tilearea.cpp b/src/tilearea.cpp
--- a/src/tilearea.cpp
+++ b/src/tilearea.cpp
@@ -118,6 +118,27 @@ bool OrthogonalTileArea::Contains(TileIn
 }
 
 /**
+ * Expand a tile area by rad tiles in each direction, keeping within map bounds.
+ * @param rad Number of tiles to expand
+ * @return The OrthogonalTileArea.
+ */
+OrthogonalTileArea &OrthogonalTileArea::Expand(int rad)
+{
+	int x = TileX(this->tile);
+	int y = TileY(this->tile);
+
+	int sx = max(x - rad, 0);
+	int sy = max(y - rad, 0);
+	int ex = min(x + this->w + rad, MapSizeX());
+	int ey = min(y + this->h + rad, MapSizeY());
+
+	this->tile = TileXY(sx, sy);
+	this->w    = ex - sx;
+	this->h    = ey - sy;
+	return *this;
+}
+
+/**
  * Clamp the tile area to map borders.
  */
 void OrthogonalTileArea::ClampToMap()