I think there are some words missing from your enquiry, and to try to guess what they are (and where they should go) might drastically change the meaning. However, here is some insight into files.
Ignoring ACLs for the moment, when a file is created, its access permissions are more dependent on the environmental settings of the process than the permissions on the directory where it is due to be located. The process's 'umask' dictates what file permissions are given to a newly created file. The permissions on the directory only dictate whether the file can be created or not (and the file doesn't usually inherit permissions from the directory it has been placed in). Using the 'setgid' permission can affect the ownership of files.
For more information see the 'man pages' for:
umask acl setgid
and the file: /etc/default/login
I hope that helps.
Mike