Set default file permission mode without ACLs

with umask:

umask 002 /the/directory

That will set the directory itself and the directories inside to have 775 permissions and the files to have 664 permissions.

The directory (and subdirectories) will have execute permissions for owner, group, and others in order to allow them to be traversed. The files will have read-write for the owner, read-write for the group, and read for others.

As mentioned below, this also depends on the processes writing to the directory. Other users with modify access can also change the umask itself or for the subdirectories inside if any exist.