diff --git a/src/qtile_bonsai/core/tree.py b/src/qtile_bonsai/core/tree.py
index 26f468a..c68dd88 100644
--- a/src/qtile_bonsai/core/tree.py
+++ b/src/qtile_bonsai/core/tree.py
@@ -14,6 +14,7 @@
 from qtile_bonsai.core.geometry import (
     Axis,
     AxisParam,
+    Box,
     Direction,
     DirectionParam,
     PerimieterParams,
@@ -110,6 +111,15 @@ def set_config(self, key: str, value: Any, *, level: int | None = None):
 
         self._config[level][key] = value
 
+    def validate_config(self):
+        """Validate config across config keys.
+
+        Raises:
+            `ValueError`: if there are any validation errors.
+        """
+        for level in self._config:
+            self._validate_tab_bar_config(level)
+
     def get_config(
         self,
         key: str,
@@ -1136,6 +1146,29 @@ def _notify_subscribers(self, event: TreeEvent, nodes: list[Node]):
         for callback in self._event_subscribers[event].values():
             callback(nodes)
 
+    def _validate_tab_bar_config(self, level: int):
+        bar_height = self.get_config(
+            "tab_bar.height", level=level, fall_back_to_default=True
+        )
+        bar_margin = self.get_config(
+            "tab_bar.margin", level=level, fall_back_to_default=True
+        )
+        bar_border_size = self.get_config(
+            "tab_bar.border_size", level=level, fall_back_to_default=True
+        )
+        bar_padding = self.get_config(
+            "tab_bar.padding", level=level, fall_back_to_default=True
+        )
+        try:
+            Box(
+                Rect(0, 0, self.width, bar_height),
+                margin=bar_margin,
+                border=bar_border_size,
+                padding=bar_padding,
+            ).validate()
+        except ValueError as err:
+            raise ValueError(f"Error in tab_bar config. {err}") from err
+
 
 def tree_matches_repr(tree: Tree, test_str: str) -> bool:
     """Tests if the provided `Tree` instance has a str representation that matches the
diff --git a/src/qtile_bonsai/layout.py b/src/qtile_bonsai/layout.py
index 1a8d68b..d208729 100644
--- a/src/qtile_bonsai/layout.py
+++ b/src/qtile_bonsai/layout.py
@@ -793,6 +793,7 @@ def _reset(self):
         # We initialize the tree with arbitrary dimensions. These get reset soon as this
         # layout's group is assigned to a screen.
         self._tree = BonsaiTree(100, 100, config=config)
+        self._tree.validate_config()
 
         self._tree.subscribe(
             TreeEvent.node_added, lambda nodes: self._handle_added_tree_nodes(nodes)
@@ -836,8 +837,6 @@ def parse_multi_level_config(self) -> BonsaiTree.MultiLevelConfig:
 
             multi_level_config[level][key] = value
 
-        validation.validate_across_options(multi_level_config)
-
         return multi_level_config
 
     def _handle_added_tree_nodes(self, nodes: list[BonsaiNodeMixin]):
diff --git a/src/qtile_bonsai/validation.py b/src/qtile_bonsai/validation.py
index 5579a89..366ff89 100644
--- a/src/qtile_bonsai/validation.py
+++ b/src/qtile_bonsai/validation.py
@@ -7,11 +7,6 @@
 from qtile_bonsai.tree import BonsaiTree
 
 
-def validate_across_options(multi_level_config: BonsaiTree.MultiLevelConfig):
-    for level, config in multi_level_config.items():
-        pass
-
-
 def validate_border_size(key: str, value: Any) -> tuple[bool, str | None]:
     if not isinstance(value, int):
         err_msg = (