diff --git a/CHANGES.rst b/CHANGES.rst
index 9d1f705d..c5802c53 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,7 +4,8 @@ Changes
 1.1rc2 (unreleased)
 -------------------
 
-- Nothing changed yet.
+- Remove no longer used ``content_grid_width`` and ``sidebar_left_grid_width``
+  properties from ``ILayoutConfig``.
 
 
 1.1rc1 (2024-05-23)
diff --git a/src/cone/app/__init__.py b/src/cone/app/__init__.py
index 4429fca4..be576a3b 100644
--- a/src/cone/app/__init__.py
+++ b/src/cone/app/__init__.py
@@ -73,8 +73,6 @@ def __init__(self, model=None, request=None):
         self.columns_fluid = True
         self.pathbar = True
         self.sidebar_left = ['navtree']
-        self.sidebar_left_grid_width = 3
-        self.content_grid_width = 9
 
 
 def import_from_string(path):
diff --git a/src/cone/app/interfaces.py b/src/cone/app/interfaces.py
index c1503b85..711af82f 100644
--- a/src/cone/app/interfaces.py
+++ b/src/cone/app/interfaces.py
@@ -95,8 +95,6 @@ class ILayoutConfig(IProperties):
     columns_fluid = Attribute(u'Flag whether columns are fluid')
     pathbar = Attribute(u'Flag whether to display pathbar')
     sidebar_left = Attribute(u'Tiles which should be rendered in sidebar')
-    sidebar_left_grid_width = Attribute(u'Sidebar grid width')
-    content_grid_width = Attribute(u'Content grid width')
 
 
 # B/C, removed as of cone.app 1.1
diff --git a/src/cone/app/testing/mock.py b/src/cone/app/testing/mock.py
index a21b36b1..b2ffcb10 100644
--- a/src/cone/app/testing/mock.py
+++ b/src/cone/app/testing/mock.py
@@ -118,8 +118,6 @@ def default_layout(context):
     config.columns_fluid = False
     config.pathbar = True
     config.sidebar_left = ['navtree']
-    config.sidebar_left_grid_width = 3
-    config.content_grid_width = 9
     return config
 
 
diff --git a/src/cone/app/tests/test_app.py b/src/cone/app/tests/test_app.py
index f27379a8..79c85055 100644
--- a/src/cone/app/tests/test_app.py
+++ b/src/cone/app/tests/test_app.py
@@ -171,8 +171,6 @@ def test_layout_config(self):
         self.assertTrue(config.columns_fluid)
         self.assertTrue(config.pathbar)
         self.assertEqual(config.sidebar_left, ['navtree'])
-        self.assertEqual(config.sidebar_left_grid_width, 3)
-        self.assertEqual(config.content_grid_width, 9)
 
         @layout_config(BaseNode)
         class BaseNodeLayout(LayoutConfig):