diff --git a/base.php b/base.php
index af41d3c..17c36f8 100644
--- a/base.php
+++ b/base.php
@@ -19,11 +19,11 @@
 
   <div class="wrap container" role="document">
     <div class="content row">
-      <main class="main <?php echo roots_main_class(); ?>" role="main">
+      <main class="main <?php echo apply_filters('roots/main_class'); ?>" role="main">
         <?php include roots_template_path(); ?>
       </main><!-- /.main -->
       <?php if (roots_display_sidebar()) : ?>
-        <aside class="sidebar <?php echo roots_sidebar_class(); ?>" role="complementary">
+        <aside class="sidebar <?php echo apply_filters('roots/sidebar_class'); ?>" role="complementary">
           <?php include roots_sidebar_path(); ?>
         </aside><!-- /.sidebar -->
       <?php endif; ?>
diff --git a/lib/config.php b/lib/config.php
index 930eb7b..5554c3f 100644
--- a/lib/config.php
+++ b/lib/config.php
@@ -28,6 +28,7 @@ function roots_main_class() {
 
   return $class;
 }
+add_filter('roots/main_class', 'roots_main_class');
 
 /**
  * .sidebar classes
@@ -35,6 +36,7 @@ function roots_main_class() {
 function roots_sidebar_class() {
   return 'col-sm-4';
 }
+add_filter('roots/sidebar_class', 'roots_sidebar_class');
 
 /**
  * Define which pages shouldn't have the sidebar