diff --git a/build.py b/build.py
index 09e5b67..e1ee714 100644
--- a/build.py
+++ b/build.py
@@ -187,7 +187,12 @@ def build_managed(output_dir: Path, cfg_name: str, config: dict):
             if item.is_file():
                 copy_path(item, managed_dir / item.name, quiet=True)
             elif item.is_dir():
-                copy_path(item, managed_dir / item.name)
+                target = managed_dir / item.name
+                if target.exists():
+                    # Merge into existing repo directory
+                    merge_into(item, target)
+                else:
+                    copy_path(item, target)
 
     # Scripts from ctrl/ -> output_dir/ctrl/ (sibling of managed, link, soleprint)
     room_ctrl = room_cfg / "ctrl"