SharePoint 2013 – Community site auto-approval option missing

The owner of a Community site has the option to control the flow of new members. By default there is a button called “Join this community”. You can set an approval to this process:

Auto-approval for permissions requests

This option is only available when you create a Community site as a root site collection. If you create a Community site as sub site the option is not available. This is by design:

http://office.microsoft.com/en-us/office365-sharepoint-online-enterprise-help/create-a-community-HA102891678.aspx#_Toc336864906

See the Configure community settings header.