diff --git a/core/modules/auto_updates/auto_updates.install b/core/modules/auto_updates/auto_updates.install
index 173d1ceaef..7994d74219 100644
--- a/core/modules/auto_updates/auto_updates.install
+++ b/core/modules/auto_updates/auto_updates.install
@@ -34,7 +34,7 @@ function auto_updates_requirements($phase) {
       ]);
     }
   }
-  elseif (\Drupal::time()->getRequestTime() > $last_check_timestamp + ReadinessCheckerManagerInterface::LAST_CHECKED_WARNING) {
+  elseif (!$checker_manager->hasRunRecently()) {
     $requirements['auto_updates_readiness']['severity'] = REQUIREMENT_ERROR;
     $time_ago = \Drupal::service('date.formatter')->formatTimeDiffSince($last_check_timestamp);
     $requirements['auto_updates_readiness']['value'] = t('Your site has not recently checked if it is ready to apply <a href="@readiness_checks">automatic updates</a>.', ['@readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']);
diff --git a/core/modules/auto_updates/auto_updates.module b/core/modules/auto_updates/auto_updates.module
index 70a68230aa..800549bec2 100644
--- a/core/modules/auto_updates/auto_updates.module
+++ b/core/modules/auto_updates/auto_updates.module
@@ -32,15 +32,14 @@ function auto_updates_page_top(array &$page_top) {
     if (in_array(\Drupal::routeMatch()->getRouteName(), $disabled_routes, TRUE)) {
       return;
     }
-    $last_check_timestamp = \Drupal::service('auto_updates.readiness_checker_manager')->timestamp();
-    if (\Drupal::time()->getRequestTime() > $last_check_timestamp + ReadinessCheckerManagerInterface::LAST_CHECKED_WARNING) {
+    /** @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker_manager */
+    $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
+    if (!$checker_manager->hasRunRecently()) {
       $readiness_settings = Url::fromRoute('auto_updates.settings');
       \Drupal::messenger()->addError(t('Your site has not recently run an update readiness check. <a href=":url">Administer automatic updates</a> and run readiness checks manually.', [
         ':url' => $readiness_settings->toString(),
       ]));
     }
-    /** @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker_manager */
-    $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
     $results = $checker_manager->getResults(ReadinessCheckerManagerInterface::ERROR);
     if ($results) {
       \Drupal::messenger()->addError(t('Your site is currently failing readiness checks for automatic updates. It cannot be <a href=":readiness_checks">automatically updated</a> until further action is performed:', [':readiness_checks' => 'https://www.drupal.org/docs/8/update/auto-updates#readiness-checks']));
@@ -82,7 +81,7 @@ function auto_updates_cron() {
 function auto_updates_modules_installed($modules) {
   /** @var ReadinessCheckerManagerInterface $checker_manager */
   $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
-  if ($checker_manager->clearResultsStaleResults()) {
+  if ($checker_manager->clearStaleResults()) {
     $checker_manager->run();
   }
 }
diff --git a/core/modules/auto_updates/auto_updates.services.yml b/core/modules/auto_updates/auto_updates.services.yml
index 461fbcd4fb..4b8c52678b 100644
--- a/core/modules/auto_updates/auto_updates.services.yml
+++ b/core/modules/auto_updates/auto_updates.services.yml
@@ -6,6 +6,6 @@ services:
       - { name: readiness_checker, category: error}
   auto_updates.readiness_checker_manager:
     class: Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManager
-    arguments: ['@keyvalue', '@config.factory']
+    arguments: ['@keyvalue', '@config.factory', '@datetime.time']
     tags:
       - { name: service_collector, tag: readiness_checker, call: addChecker }
diff --git a/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
index 69bd3f6b22..42bd0acda4 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
@@ -10,12 +10,12 @@
 class DiskSpace extends FilesystemBase {
 
   /**
-   * Minimum disk space (in bytes) is 10mb.
+   * Minimum disk space (in bytes) is 100mb.
    *
    * @todo Determine how much the minimum should be now that we will be using
-   *   Composer.
+   *   Composer in https://www.drupal.org/node/3166416.
    */
-  const MINIMUM_DISK_SPACE = 10000000;
+  const MINIMUM_DISK_SPACE = 100000000;
 
   /**
    * Megabyte divisor.
@@ -45,7 +45,7 @@ protected function diskSpaceCheck() {
           '@space' => $minimum_megabytes,
         ]);
       }
-      if (is_dir($this->getVendorPath()) && disk_free_space($this->getVendorPath()) < static::MINIMUM_DISK_SPACE) {
+      if (disk_free_space($this->getVendorPath()) < static::MINIMUM_DISK_SPACE) {
         $messages[] = $this->t('Vendor filesystem "@vendor" has insufficient space. There must be at least @space megabytes free.', [
           '@vendor' => $this->getVendorPath(),
           '@space' => $minimum_megabytes,
diff --git a/core/modules/auto_updates/src/ReadinessChecker/FilesystemBase.php b/core/modules/auto_updates/src/ReadinessChecker/FilesystemBase.php
index 622b7795d1..9b5c4b0f3a 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/FilesystemBase.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/FilesystemBase.php
@@ -17,13 +17,6 @@ abstract class FilesystemBase implements ReadinessCheckerInterface {
    */
   protected $rootPath;
 
-  /**
-   * The vendor file path.
-   *
-   * @var string
-   */
-  protected $vendorPath;
-
   /**
    * Filesystem constructor.
    *
@@ -38,10 +31,18 @@ public function __construct(string $app_root) {
    * {@inheritdoc}
    */
   public function run() {
+    $messages = [];
     if (!file_exists($this->getRootPath() . DIRECTORY_SEPARATOR . implode(DIRECTORY_SEPARATOR, ['core', 'core.api.php']))) {
-      return [$this->t('The web root could not be located.')];
+      $messages[] = $this->t('The web root could not be located.');
+    }
+    if (!is_dir($this->getVendorPath())) {
+      $messages[] = $this->t('Vendor folder "@vendor" is not a valid directory. Alternate vendor folder locations are not currently supported.', [
+        '@vendor' => $this->getVendorPath(),
+      ]);
+    }
+    if ($messages) {
+      return $messages;
     }
-
     return $this->doCheck();
   }
 
@@ -60,9 +61,6 @@ public function run() {
    *   The root file path.
    */
   protected function getRootPath() {
-    if (!$this->rootPath) {
-      $this->rootPath = (string) \Drupal::root();
-    }
     return $this->rootPath;
   }
 
@@ -73,10 +71,9 @@ protected function getRootPath() {
    *   The vendor file path.
    */
   protected function getVendorPath() {
-    if (!$this->vendorPath) {
-      $this->vendorPath = $this->getRootPath() . DIRECTORY_SEPARATOR . 'vendor';
-    }
-    return $this->vendorPath;
+    // @todo Support finding the 'vendor' directory dynamically in
+    // https://www.drupal.org/node/3166435.
+    return $this->getRootPath() . DIRECTORY_SEPARATOR . 'vendor';
   }
 
   /**
diff --git a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
index e813912603..42e2059156 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\auto_updates\ReadinessChecker;
 
+use Drupal\Component\Datetime\TimeInterface;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\KeyValueStore\KeyValueFactoryInterface;
 
@@ -10,6 +11,11 @@
  */
 class ReadinessCheckerManager implements ReadinessCheckerManagerInterface {
 
+  /**
+   * Last checked ago warning (in seconds).
+   */
+  private const LAST_CHECKED_WARNING = 3600 * 24;
+
   /**
    * The key/value storage.
    *
@@ -34,6 +40,13 @@ class ReadinessCheckerManager implements ReadinessCheckerManagerInterface {
    */
   protected $checkers = [];
 
+  /**
+   * The time service.
+   *
+   * @var \Drupal\Component\Datetime\TimeInterface
+   */
+  protected $time;
+
   /**
    * ReadinessCheckerManager constructor.
    *
@@ -41,10 +54,13 @@ class ReadinessCheckerManager implements ReadinessCheckerManagerInterface {
    *   The key/value service.
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
    *   The config factory.
+   * @param \Drupal\Component\Datetime\TimeInterface $time
+   *   The time service.
    */
-  public function __construct(KeyValueFactoryInterface $key_value, ConfigFactoryInterface $config_factory) {
+  public function __construct(KeyValueFactoryInterface $key_value, ConfigFactoryInterface $config_factory, TimeInterface $time) {
     $this->keyValue = $key_value->get('auto_updates');
     $this->configFactory = $config_factory;
+    $this->time = $time;
   }
 
   /**
@@ -81,7 +97,7 @@ public function run() {
         'checkers' => $this->getCurrentCheckerIds(),
       ]
     );
-    $this->keyValue->set('readiness_check_timestamp', \Drupal::time()->getRequestTime());
+    $this->keyValue->set('readiness_check_timestamp', $this->time->getRequestTime());
     return $messages_by_category;
   }
 
@@ -100,7 +116,7 @@ public function getResults($category) {
   /**
    * {@inheritdoc}
    */
-  public function clearResultsStaleResults() {
+  public function clearStaleResults() {
     $results = $this->keyValue->get('readiness_check_results');
     if (isset($results['checkers']) && $this->getCurrentCheckerIds() !== $results['checkers']) {
       $this->keyValue->delete('readiness_check_results');
@@ -133,10 +149,10 @@ public function getCategories() {
   /**
    * Sorts checkers according to priority.
    *
-   * @return \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerInterface[]
-   *   A sorted array of checker objects.
-   *
-   * @todo Add more detail to @return.
+   * @return \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerInterface[][]
+   *   A nested and sorted array of checker objects. The first level of the
+   *   array is keyed by checker categories. The second level array is checker
+   *   objects in the category order by priority.
    */
   protected function getSortedCheckers() {
     $sorted = [];
@@ -166,4 +182,11 @@ protected function getCurrentCheckerIds(): string {
     return implode('::', $service_ids);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function hasRunRecently() {
+    return !($this->time->getRequestTime() > $this->timestamp() + self::LAST_CHECKED_WARNING);
+  }
+
 }
diff --git a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
index b794df6af0..be26011f3f 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
@@ -17,11 +17,6 @@ interface ReadinessCheckerManagerInterface {
    */
   const WARNING = 'warning';
 
-  /**
-   * Last checked ago warning (in seconds).
-   */
-  const LAST_CHECKED_WARNING = 3600 * 24;
-
   /**
    * Appends a checker to the checker chain.
    *
@@ -90,6 +85,14 @@ public function getCategories();
    * @return bool
    *   Return TRUE if the results were cleared, otherwise returns FALSE.
    */
-  public function clearResultsStaleResults();
+  public function clearStaleResults();
+
+  /**
+   * Determines whether the readiness checkers have been run recently.
+   *
+   * @return bool
+   *   True if the checkers have been run recently, otherwise false.
+   */
+  public function hasRunRecently();
 
 }
diff --git a/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php b/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
index 51a09e5aad..08066f8dcf 100644
--- a/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
+++ b/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
@@ -42,6 +42,13 @@ public function testDiskSpace() {
     $this->assertStringMatchesFormat('Drupal root filesystem "%s" has insufficient space. There must be at least %s megabytes free.', (string) $messages[0]);
     $this->assertStringMatchesFormat('Vendor filesystem "%s" has insufficient space. There must be at least %s megabytes free.', (string) $messages[1]);
     $this->assertStringMatchesFormat('Directory "%s" has insufficient space. There must be at least %s megabytes free.', (string) $messages[2]);
+
+    // Web root and vendor path are invalid.
+    $disk_space = new DiskSpace("if_there_was_ever_a_folder_with_this_path_this_test_would_fail");
+    $messages = $disk_space->run();
+    $this->assertCount(2, $messages);
+    $this->assertEquals('The web root could not be located.', (string) $messages[0]);
+    $this->assertStringMatchesFormat('Vendor folder "if_there_was_ever_a_folder_with_this_path_this_test_would_fail/vendor" is not a valid directory. Alternate vendor folder locations are not currently supported.', (string) $messages[1]);
   }
 
 }