diff --git a/core/includes/file.inc b/core/includes/file.inc
index 3e5eb8c..16fdf8a 100644
--- a/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -332,7 +332,17 @@ function file_ensure_htaccess() {
     file_save_htaccess('private://', TRUE);
   }
   file_save_htaccess('temporary://', TRUE);
-  file_save_htaccess(config_get_config_directory(CONFIG_SYNC_DIRECTORY), TRUE);
+
+  // If a staging directory exists then it should contain a .htaccess file.
+  try {
+    $staging = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+  }
+  catch (\Exception $e) {
+    $staging = FALSE;
+  }
+  if ($staging) {
+    file_save_htaccess($staging, TRUE);
+  }
 }
 
 /**
diff --git a/core/modules/config/config.install b/core/modules/config/config.install
new file mode 100644
index 0000000..c971ae6
--- /dev/null
+++ b/core/modules/config/config.install
@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the config module.
+ */
+
+/**
+* Implements hook_requirements().
+*/
+function config_requirements($phase) {
+  $requirements = [];
+  try {
+    $directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+  }
+  catch (\Exception $e) {
+    // system_requirements() guarantees that the CONFIG_SYNC_DIRECTORY exists
+    // as the config.storage.staging service relies on it.
+    $directory = FALSE;
+  }
+  // Ensure the configuration sync directory is writable. This is only a warning
+  // because only configuration import from a tarball requires the folder to be
+  // web writable.
+  if ($phase !== 'install' && !is_writable($directory)) {
+    $requirements['config directory ' . CONFIG_SYNC_DIRECTORY] = [
+      'title' => t('Configuration directory: %type', ['%type' => CONFIG_SYNC_DIRECTORY]),
+      'description' => t('The directory %directory is not writable.', ['%directory' => $directory]),
+      'severity' => REQUIREMENT_WARNING,
+    ];
+  }
+  return $requirements;
+}
diff --git a/core/modules/config/src/Form/ConfigImportForm.php b/core/modules/config/src/Form/ConfigImportForm.php
index c16dfe8..733e1d1 100644
--- a/core/modules/config/src/Form/ConfigImportForm.php
+++ b/core/modules/config/src/Form/ConfigImportForm.php
@@ -72,6 +72,11 @@ public function buildForm(array $form, FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function validateForm(array &$form, FormStateInterface $form_state) {
+    $directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+    if (!is_writable($directory)) {
+      $form_state->setErrorByName('import_tarball', $this->t('The directory %directory is not writable.', ['%directory' => $directory]));
+    }
+
     $file_upload = $this->getRequest()->files->get('files[import_tarball]', NULL, TRUE);
     if ($file_upload && $file_upload->isValid()) {
       $form_state->setValue('import_tarball', $file_upload->getRealPath());
diff --git a/core/modules/config/src/Tests/ConfigImportUploadTest.php b/core/modules/config/src/Tests/ConfigImportUploadTest.php
index 33f6171..da1e159 100644
--- a/core/modules/config/src/Tests/ConfigImportUploadTest.php
+++ b/core/modules/config/src/Tests/ConfigImportUploadTest.php
@@ -50,6 +50,12 @@ function testImport() {
     $edit = array('files[import_tarball]' => drupal_realpath($text_file->uri));
     $this->drupalPostForm('admin/config/development/configuration/full/import', $edit, t('Upload'));
     $this->assertText(t('Could not extract the contents of the tar file'));
+
+    // Make the sync directory read-only.
+    $directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+    \Drupal::service('file_system')->chmod($directory, 0555);
+    $this->drupalPostForm('admin/config/development/configuration/full/import', $edit, t('Upload'));
+    $this->assertRaw(t('The directory %directory is not writable.', ['%directory' => $directory]));
   }
 
 }
diff --git a/core/modules/config/src/Tests/ConfigInstallWebTest.php b/core/modules/config/src/Tests/ConfigInstallWebTest.php
index 221d09f..a192e9b 100644
--- a/core/modules/config/src/Tests/ConfigInstallWebTest.php
+++ b/core/modules/config/src/Tests/ConfigInstallWebTest.php
@@ -31,7 +31,7 @@ class ConfigInstallWebTest extends WebTestBase {
   protected function setUp() {
     parent::setUp();
 
-    $this->adminUser = $this->drupalCreateUser(array('administer modules', 'administer themes'));
+    $this->adminUser = $this->drupalCreateUser(array('administer modules', 'administer themes', 'administer site configuration'));
 
     // Ensure the global variable being asserted by this test does not exist;
     // a previous test executed in this request/process might have set it.
@@ -192,4 +192,23 @@ public function testUnmetDependenciesInstall() {
     $this->rebuildContainer();
     $this->assertTrue(entity_load('config_test', 'other_module_test_with_dependency'), 'The config_test.dynamic.other_module_test_with_dependency configuration has been created during install.');
   }
+
+  /**
+   * Tests config_requirements().
+   */
+  public function testConfigModuleRequirements() {
+    $this->drupalLogin($this->adminUser);
+    $this->drupalPostForm('admin/modules', array('modules[Core][config][enable]' => TRUE), t('Install'));
+
+    $directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+    file_unmanaged_delete_recursive($directory);
+    $this->drupalGet('/admin/reports/status');
+    $this->assertRaw(t('The directory %directory does not exist.', array('%directory' => $directory)));
+
+    file_prepare_directory($directory, FILE_CREATE_DIRECTORY);
+    \Drupal::service('file_system')->chmod($directory, 0555);
+    $this->drupalGet('/admin/reports/status');
+    $this->assertRaw(t('The directory %directory is not writable.', ['%directory' => $directory]));
+  }
+
 }
diff --git a/core/modules/system/src/Tests/System/StatusTest.php b/core/modules/system/src/Tests/System/StatusTest.php
index 5bb9578..130a709 100644
--- a/core/modules/system/src/Tests/System/StatusTest.php
+++ b/core/modules/system/src/Tests/System/StatusTest.php
@@ -29,6 +29,16 @@ class StatusTest extends WebTestBase {
   protected function setUp() {
     parent::setUp();
 
+    // Unset the sync directory in settings.php to trigger $config_directories
+    // error.
+    $settings['config_directories']  = array(
+      CONFIG_SYNC_DIRECTORY => (object) array(
+        'value' => '',
+        'required' => TRUE,
+      ),
+    );
+    $this->writeSettings($settings);
+
     $admin_user = $this->drupalCreateUser(array(
       'administer site configuration',
     ));
@@ -65,6 +75,9 @@ public function testStatusPage() {
     // If a module is fully installed no pending updates exists.
     $this->assertNoText(t('Out of date'));
 
+    // blah
+    $this->assertRaw(t('Your %file file must define the $config_directories variable as an array containing the name of a directories in which configuration files can be written. It must contain a %sync_key key.', array('%file' => $this->siteDirectory . '/settings.php', '%sync_key' => CONFIG_SYNC_DIRECTORY)));
+
     // Set the schema version of update_test_postupdate to a lower version, so
     // update_test_postupdate_update_8001() needs to be executed.
     drupal_set_installed_schema_version('update_test_postupdate', 8000);
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 44212b1..d57a1a3 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -548,15 +548,22 @@ function system_requirements($phase) {
   // defined, the installer will create a valid config directory later, but
   // during runtime we must always display an error.
   if (!empty($GLOBALS['config_directories'])) {
-    foreach ($GLOBALS['config_directories'] as $type => $directory) {
-      $directories[] = config_get_config_directory($type);
+    foreach (array_keys(array_filter($GLOBALS['config_directories'])) as $type) {
+      $directory = config_get_config_directory($type);
+      if (!is_dir($directory)) {
+        $requirements['config directory ' . $type] = array(
+          'title' => t('Configuration directory: %type', ['%type' => $type]),
+          'description' => t('The directory %directory does not exist.', array('%directory' => $directory)),
+          'severity' => REQUIREMENT_ERROR,
+        );
+      }
     }
   }
-  elseif ($phase != 'install') {
+  if ($phase != 'install' && (empty($GLOBALS['config_directories']) || empty($GLOBALS['config_directories'][CONFIG_SYNC_DIRECTORY]) )) {
     $requirements['config directories'] = array(
       'title' => t('Configuration directories'),
       'value' => t('Not present'),
-      'description' => t('Your %file file must define the $config_directories variable as an array containing the name of a directories in which configuration files can be written.', array('%file' => $site_path . '/settings.php')),
+      'description' => t('Your %file file must define the $config_directories variable as an array containing the name of a directories in which configuration files can be written. It must contain a %sync_key key.', array('%file' => $site_path . '/settings.php', '%sync_key' => CONFIG_SYNC_DIRECTORY)),
       'severity' => REQUIREMENT_ERROR,
     );
   }