diff --git a/lib/permissions/thread-permissions.js b/lib/permissions/thread-permissions.js
--- a/lib/permissions/thread-permissions.js
+++ b/lib/permissions/thread-permissions.js
@@ -405,6 +405,47 @@
   return getRolePermissionBlobsForCommunity(threadType);
 }
 
+function getUniversalCommunityRootPermissionsBlob(
+  threadType: ThreadType,
+): ThreadRolePermissionsBlob {
+  const openDescendantKnowOf = DESCENDANT + OPEN + threadPermissions.KNOW_OF;
+  const openDescendantVoiced = DESCENDANT + OPEN + threadPermissions.VOICED;
+  const openDescendantVisible = DESCENDANT + OPEN + threadPermissions.VISIBLE;
+  const openChildJoinThread = CHILD + OPEN + threadPermissions.JOIN_THREAD;
+  const openTopLevelDescendantJoinThread =
+    DESCENDANT + OPEN_TOP_LEVEL + threadPermissions.JOIN_THREAD;
+
+  const genesisUniversalCommunityPermissions = {
+    [threadPermissions.KNOW_OF]: true,
+    [threadPermissions.VISIBLE]: true,
+    [openDescendantKnowOf]: true,
+    [openDescendantVisible]: true,
+    [openTopLevelDescendantJoinThread]: true,
+  };
+
+  const baseUniversalCommunityPermissions = {
+    ...genesisUniversalCommunityPermissions,
+    [threadPermissions.JOIN_THREAD]: true,
+    [threadPermissions.CREATE_SIDEBARS]: true,
+    [threadPermissions.LEAVE_THREAD]: true,
+    [openDescendantVoiced]: true,
+    [openChildJoinThread]: true,
+  };
+
+  if (threadType === threadTypes.GENESIS) {
+    return genesisUniversalCommunityPermissions;
+  } else if (threadType === threadTypes.COMMUNITY_ANNOUNCEMENT_ROOT) {
+    return baseUniversalCommunityPermissions;
+  } else if (threadType === threadTypes.COMMUNITY_ROOT) {
+    return {
+      ...baseUniversalCommunityPermissions,
+      [threadPermissions.VOICED]: true,
+    };
+  } else {
+    return {};
+  }
+}
+
 export {
   permissionLookup,
   getAllThreadPermissions,
@@ -412,4 +453,5 @@
   makePermissionsForChildrenBlob,
   getRoleForPermissions,
   getRolePermissionBlobs,
+  getUniversalCommunityRootPermissionsBlob,
 };