CentOS - Aug 2014 - Upgrade to m7.0 retaining some existing partitions

Hi,

I want to install 7.0 replacing  an existing 6.5 installation.

When I choose custom partitioning I can delete the old 6.5 partitions 
and create new partitions 7.0 but there doesn't appear to be any way 
to retain an existing partition, say /home for instance, over the 
installation.

Am I just missing something obvious or any ideas on what the magic is.

Regards,

Tony
-- 
Linux nogs.tonyshome.ie 2.6.32-431.23.3.el6.x86_64 #1 SMP Thu Jul 31 
17:20:51 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux